Pen-Write E-Library

TOPIC: Heat Energy, Concept of Heat and Temperature and Effects of Heat
CONTENT
 Concept of Heat
 Temperature
 Effect of Heat on bodies.

Concept of Heat
Heat is a concept of physics that deals with the study of relative motion of fluid (liquid and gas) from one body to another. It is a form of energy that can be transferred from one body due to temperature differences.

Temperature
Temperature is the degree of hotness and coldness of a body or an object. It is a scalar quantity, measured in Kelvin. Heat and Temperature are similar but not the same
https://youtu.be/LL54E5CzQ-A

Differences Between Heat and Temperature
1. Heat is a measure of the total internal energy of a body while temperature is the degree of hotness or coldness of the body.
2. Heat takes place due to temperature difference while temperature occurs due to slight change of substance.
3. Heat is measured in joules while temperature is measured in Kelvin / Celsius.

Effect of Heat
When heat is applied to a body the following effect may occur
1. Expansion: when heat is applied, volumes increases while density decreases.
2. Change in temperature: When heat is added on a body, the temperature increases
3. Change of state : melting, freezing, condensation, evaporation etc.
4. Thermion emission : Addition of heat on metal may result in the emission of electron from the surface of the metal
5. Photo electric emission: The emission of electron when sufficient light of high frequency is illuminated on a metal surface e.g. zinc plate.
https://youtu.be/2wqtK3GNFdQ
EVALUATION
1. Differentiate between heat and temperature
2. Mention five effect of heat
Reading Assignment-www.google.com(click on google search, type “concept of heat”,click on search) and New School Physics pg36

ASSIGNMENT
1 . Which of the following is not an effect of heat? (a) expansion (b) contraction (c) change of state. (d) increase in weight
2. Temperature can be measured in the following units except (a) degree celsius (b) kelvin (c) degree Fahrenheit (d) centigrade-meter
3. When heat is extracted from water it changes from liquid to gas. What is this process called....................
4. The process of by which a gas is converted to a solid is called .................
5. farenheit is a unit of ...............................

THEORY
1. Differentiate between heat and temperature.
2. Mention five effect of heat.





TOPIC: RECTILINEAR ACCELERATION:
CONTENT:
Concept of acceleration - Uniform/non-uniform acceleration, deceleration
Worked examples on acceleration and deceleration.

CONCEPT OF ACCELERATION
When an object increases or changes its velocity within a set time, the object is said to undergo acceleration (or to accelerate). We therefore define acceleration as the rate of change of velocity with time.

i.e, acceleration=(change in velocity)/(time taken)

∴ a=(v-u)/t

Where
a: acceleration
v: final velocity
u: initial velocity

Acceleration is a vector quantity and its SI unit is m/s2.
However, still be reminded that:
When a body starts from rest, its initial velocity, ‘u’ is zero.
When a body comes to rest, its final velocity, ‘v’ is zero.

https://youtu.be/Sz-1Hg8_l-0

UNIFORM AND NON-UNIFORM ACCELERATION
Acceleration is said to be uniform if the velocity increases by equal amounts in equal intervals of time. That is, the rate of change of velocity with time is constant. If the rate of change of velocity with time is not constant, then, the acceleration is non-uniform.
https://youtu.be/Ravz8_jz15w

DECELERATION
Deceleration is defined as a negative change in velocity with time. When such happens, the body is said to be coming to rest.
Deceleration is said to be uniform if the velocity decreases by equal amounts in equal intervals of time. That is, the negative change in velocity with time is constant.

Also, deceleration = (change in velocity)/(time taken) = (v-u)/t

Deceleration is also called retardation and its SI unit is m/s2. It is also a vector quantity.
https://youtu.be/0EdTeT7HHZ8

Evaluation:
1. Define acceleration.
2. Differentiate between acceleration and deceleration.
3. Quote the formula for acceleration and its SI unit.


WORKED EXAMPLES ON ACCELERATION & DECELERATION
Ex 1: A body experienced a change in velocity of 10m/s in 15s. What is the acceleration of the body?
Solution:
Data: ∆v=10m/s ,t=15s,a=?

Now,a = ∆v/∆t=10/15

∴ a = 0.67m/s2



Ex 2: A car accelerated uniformly at 6m/s^2 in 20s. What was the change in velocity?
Solution:

Data: a = 6m/s2 , t = 20s, ∆v = ?

Now, a = ∆v/∆t

∴ ∆v = a×∆t
∴ ∆v = 6×20
∴ ∆v = 120m/s



Ex 3: The velocity of a lorry decreased from 60km/h to 35km/h within 0.5mins. Find the deceleration.
Solution:

Data: u=60km/h=(60×1000)/(60×60) = 60,000/3600 = 16.67m/s ,
v = 35km/h = 9.72m/s, t = 0.5mins = 30s, d = ?

Now, d = ∆v/∆t = (v-u)/t = (9.72-16.67)/30 =-6.95/30

∴ d=-0.23m/s2
The negative sign shows that it is decelerating thus coming to rest.



https://youtu.be/k8w1iuvATSc

Evaluation:
Find the deceleration of a car whose change in velocity within a time interval of 10s is -30m/s.

GENERAL EVALUATION:
1. What is the similarity between acceleration and deceleration?
2. Differentiate between acceleration and deceleration.
3. Write down the formula for acceleration.

ASSIGNMENT
1. The SI unit of acceleration is ---

(a) m/s2 (b) m/s (c ) m2/s (d) ms

2. A car starts from rest and accelerates uniformly at 2m/s2 for 4s. The velocity attained at this time is ---
2m/s
4m/s
6m/s
8m/s
3. a lorry moving with uniform acceleration accelerate from 20m/s to 80m/s in 2 seconds. What is the acceleration of the lorry?
30m/s2
250m/s2
1250m/s2
100m/s2
4. Which of the below statements describe deceleration?
A positive change in velocity with time.
A negative change in velocity with time.
A uniform change in velocity with time.
A constant change in velocity with time.
5. One of the below physical quantities has the same SI unit with acceleration.
Impulse
Velocity
Retardation
Displacement
Essay
A car started from rest and accelerates uniformly until it reaches a maximum velocity of 80km/h in 20s. It is then brought to rest in further 12s. Find the deceleration of the car.

READING ASSIGNMENT
Read up the topic: ‘’Velocity-Time Graph’’ in the following text books.
Senior Secondary School Physics by P.N. Okeke et al.
New School Physics for Senior Secondary Schools by Anyakoha, M.W.

TOPIC : Thermometer and Its Type. Evaporation and Boiling
CONTENT
 Thermometer And Their Thermometric Substance
 Fixed Point of Thermometer
 Evaporation and Boiling

Thermometer and Their Thermometric Substance
Thermometric substances are substances which changes in proportion to temperature.


ADVANTAGES OF MERCURY AS A THERMOMETRIC SUBSTANCE.
1. Mercury does not wet glass
2. Mercury response quickly to slight change in temperature
3. The liquid does not vaporize easily
4. Mercury is opaque Hence, it can be seen easily
5. It has a regular or uniform expansion.

DISADVANTAGES
1. Mercury is expensive
2. Mercury can not be used to measure very low temperature because it’s freezing point - 39˚C

ADVANTAGES OF ALCOHOL AS A THERMOMETRIC SUBSTANCE
1. Alcohol is less expensive than mercury
2. It has larger expansion on heating than mercury (it expands 6 times more than mercury).
3. It can be used to measure very low temperature.

DISADVANTAGES
1. It is not opaque and so most be colored
2. It vaporizes easily
3. It wet glass
4. It has an irregular expansion
5. It has low boiling point of 78˚C

CONSTANT VOLUME GAS THERMOMETER
1. It gives more accurate measurement of temperature than any other thermometer
2. It is very sensitive and can measure wider range of temperature

DISADVANTAGES
1. It is very expensive and so require handling with special care
2. It is very cumbersome

EVALUATION
1. What advantage does a constant volume gas thermometer has over other thermometers?
2. Mention five types of thermometer, their thermometric substance and physical property

FIXED POINT OF THERMOMETER
Fixed temperature point are two reference temperature (usually upper and lower fix point) chosen, when preparing a scale for reading temperatures.
Upper Fixed Point: is the temperature of steam from pure water at the normal atmospheric pressure.
Lower Fixed Point: is the temperature of mixture of pure ice and water at normal pressure.
Fundamental Intervals: is the interval between the upper and lower fixed point.


REASON WHY WATER IS NOT USED AS A THERMOMETRIC
1. Water wet glass
2. They are colour less
3. It does not expand uniformly
4. It has small range of expansion (0˚C to 100˚C)

CLINICAL THERMOMETER
It is used for measuring the temperature of human body. The body temperature ranges from (35˚C to 45˚C). It is not advisable to sterilize a clinical thermometer in boiling water because a short range of 35˚C to 43˚C which shall result to
1. Cracking or breaking of thermometer due to excessive expansion of the mercury.
2. Demal function of the thermometer due to over expansion of the capillary tube and the mercury inside the bulb.




Evaporation and Boiling
Evaporation is the process where a liquid turns into vapour below its boiling point. Evaporation takes place at all temperature. Wind assist evaporation
Boling is the change from liquid to vapour at the boilng point. It occurs throughout the entire volume of the liquid. Wind has no effect on boiling

https://youtu.be/qL2ct9d_cMc

EVALUATION
1. Why is water not used as a thermometric substance
2. Differentiate between evaporation and boiling
Reading Assignment-www.google.com(click on google search, type “temperature & its measurement”, click on search) and New School Physics pg 202 - 209

ASSIGNMENT
1. The clinical thermometer is characterized by having a (a)wide range of temperature (b) wide bore (c) long stem (d) constriction
2. A short response time is obtained in a liquid - in-glass thermometer when the (a) bulb is large and thiclk walled (b) bulb is small and thin walled (c) stem is long and thin (d)bulb is thin walled and the liquid is a good conductor of heat.
3. Change in volume with temperature is the physical propety of ………. thermometer (a) constant volume gas (b) liquid-in-glass (c) resistant (d) thermoelectric
4. Convert 27ºC to kelvin (a) 290K (b) 300K (c) 300ºC (d) 310K
5. The following are units of temperature except (a) kelvin (b) degree Celsius (c) ampere (d) Fahrenheit


THEORY
1. Mention five types of thermometer, their thermometric substance and physical property
2. Why is it not advisable to sterilize a clinical thermometer in boiling water






TOPIC: RECTILINEAR ACCELERATION (CONT):
Velocity-time graphs.
Worked Examples on v-t graphs
Analysis of rectilinear motion.


VELOCITY-TIME (v-t) GRAPH.
When the velocity of a body moving uniformly is plotted against the time, a straight line is obtained and the slope gives the acceleration or deceleration depending on the ascending or descending nature of the graph. This is shown below.



The slope of line OA gives the acceleration. ∴a=∆v/∆t It is a positive value because the graph ascends from left to right.



The slope of line BC gives the deceleration. ∴ d =-∆v/∆t It is a negative value because the graph descends from left to right.

Supposing a body accelerates from rest until it attains a final velocity v in time t1 and then brought to rest in time t2, the v-t graph is shown below.


(i) Slope of line OA gives acceleration.
(ii) Slope of line AB gives deceleration.
(iii) Area of ∆OAC gives the distance travelled during the acceleration.
(iv) Area of ∆ABC gives the distance travelled during the deceleration.
(v) Area of the whole shape, ∆OAB gives the total distance travelled. You can equally add up the distances in (iii) and (iv) above to give the total distance travelled.

Supposing another body now accelerates uniformly from rest until it reaches a final velocity V in time, t1 and continues with uniform

speed at this velocity in time, t2 then brought to rest in a further time , t3, the v-t graph is shown below:



(i) Slope of line OA gives the acceleration.
(ii) Slope of line BC gives the retardation.
(iii) Area of ∆OAE gives the distance covered during the acceleration.
(iv) Area of rectangle ABDE gives the distance travelled during the uniform speed.
(v) Area of ∆BCD gives the distance travelled during the deceleration.
(iv) Area of the whole shape (trapezium OABC) gives the total distance travelled during the entire journey.
You can also add up the distances in (iii), (iv) & (v) to get the total distance travelled during the entire journey.
https://youtu.be/b0VKlpetP9A

EVALUATION
Examine the below v-t graph and answer the questions that follows.


(i) Area of rectangle OVAC will give ---
(ii) Area of triangle ABC will give ---
(iii) How would you find the total distance travelled?
(iv) Did the body accelerate?
(v) The slope of line AB will give ---
(vi) Did the body start from rest?
(vii) Briefly discuss the motion of the body.


WORKED EXAMPLES ON V-T GRAPH

1. A body starts from rest and accelerates at 2m/s2 until it gets to a final velocity in 20s. It is then brought to rest in another 10s. With the aid of a v-t graph, find the final velocity attained and the total distance travelled.
Solution:


i) Slope of line OA = acceleration

∴ a = ∆y/∆x = (A-C)/(C-O) = (V-0)/(20-0)

∴ a = V/20

∴ V = 2×20

Hence, V=40m/s


ii) Total distance travelled is the area of the whole shape =area of ∆OAB=½bh = ½(OB)(AC)
Note that VO = AC

∴Total distance covered=½ (30)(40)=(30×40)/2

Hence, total distance travelled= 1200/2 = 600m
https://youtu.be/YCVSQp428GI

2. A car starts from rest and accelerates uniformly at xm/s^2 until it reaches a final velocity of 60m/s in 23s. It is then brought to rest for further 15s.

1. Sketch the v-t graph.
2. Find the value of x
3. Find the distance travelled during the acceleration and the deceleration.
4. Find the total distance travelled.

Solution:
i)

ii) Acceleration=slope of line OP=∆y/∆x

∴x=(P-R)/(R-O)=(60-0)/(23-0)

∴x=60/23

∴x=2.6m/s2

Hence, the acceleration of that car is 2.6m/s2

iii) Distance travelled during the acceleration is the area of ∆OPR=½bh= ½(OR)(PR)

Note that PR=60

∴Distance travelled=½(23)(60)=(23×60)/2 = 690m

Hence, the distance covered during the acceleration=690m

For the distance covered during the deceleration, it is area of ∆PQR = ½bh= ½(QR)(PR)

Note that PR=60

∴Distance travelled during the deceleration=½(15)(60)=(15×60)/2 = 450m

Hence, the distance covered during the deceleration=450m

iii) Total distance travelled = 690m + 450m = 1,140m

Alternatively, total distance travelled is the area of the whole shape =area of ∆OPQ = ½(OQ)(PR)

Note that PR=60

Total distance travelled = ½(38)(60)=(38×60)/2=1,140m
https://youtu.be/ON4m9_BvTKg

Evaluation
A car starts from rest and accelerates uniformly at 8m/s^2 until it attains a maximum velocity of 80m/s in 10s. It continues with this speed for further 100s until it is brought to rest for another 25s. Using a v-t graph, find the total distance travelled.



ANALYSIS OF RECTILINEAR MOTION.
Supposing a body moving at an initial velocity 'u' later attains a final velocity 'v' in time t,
Its acceleration is given as:

a=(change in velocity)/(time taken)

∴a=(v-u)/t-----(1)

By making v subject of the formula,

We have v=u+at-----(2)

Recall that speed = distance/time

∴v=s/t

∴s=vt


Since the body above experienced two velocities, u & v, thus, the average velocity is (v+u)/2

Hence, s=(v+u)t/2-----(3)

Putting (2) into (3), we have

s=(u+at+u)t/2=(2ut+at2)/2=2ut/2+(at2)/2

Hence, s=ut+½ (at2 )-----(4)

From (1),

t=(v-u)/a-----(5)

Putting (5) into (3), we have

s=(v+u)/2×(v-u)/a=(v+u)(v-u)/2a

But (v+u)(v-u) is a different of two squares, implying that (v+u)(v-u)=v2-u2

Hence, s=(v2-u2)/2a

Making v2 subject of the formula, we have

v2=u2+2as------(6)



Thus, in summary, the equations of motion include:
v=u+at

s=ut+½ at2

v2=u2+2as

Under gravity, for a body descending, g is +ve. Therefore, the above equations become:
v = u+gt

s=ut+½ gt2

v2=u2+2gs

Under gravity, for a body ascending, g is-ve. Therefore, the above equations become:
v=u-gt

s=ut-½ gt2

v2=u2-2gs
https://youtu.be/GX5zToM_Vvg

WORKED EXAMPLES
1. A body starts from rest and accelerates at 2m/s2 until it gets to a final velocity in 20s. It is then brought to rest in another 10s. Using equations, find the final velocity attained and the total distance travelled.
Solution:


2. A car starts from rest and accelerates uniformly at xm/s2 until it reaches a final velocity of 60m/s in 23s. It is then brought to rest for further 15s. Using equations,

1. find the value of x
2. find the distance travelled during the acceleration and the deceleration.
3. find the total distance travelled.

Solution:


https://youtu.be/Avv05JX3lX4

Evaluation
A car starts from rest and accelerates uniformly at 8m/s^2 until it attains a maximum velocity of 80m/s in 10s. It continues with this speed for further 100s until it is brought to rest for another 25s. Using equations, find the total distance travelled.

https://youtu.be/0YsudDWJlf8

GENERAL EVALUATION:
1. Write down the equations of motion.
2. Write down the various transformation of the above equations under gravity.

ASSIGNMENT:
1. The following are equations of motion. Except ---
A. v=u+at

B. s=ut+½at2

C. s=(v+u)t/2

D. V2=u2+at2

2. When velocity is plotted against the time taken, the gradient of the uniform graph obtained gives ---
[A.] Speed
[B.Deceleration
[C]Acceleration
[D]Uniform speed
3. In a v-t graph, area of the entire shape obtained gives ---
[A]Acceleration
[B.]Deceleration
[C]Distance
[D]Total distance travelled
4. For a body thrown upward, its acceleration is usually ---
[A]Negative
[B.]Neutral
[C]Positive
[D]Valueless
5. When a body comes to rest, the final velocity is ---
[A]Neutral
[B.]Zero
[C]Uniform
[D]Constant
Essay
1. Derive the equations of motion.
2. What is the acceleration of a body at uniform speed?

READING ASSIGNMENT
Read up the topic: ‘’Scalars and Vectors’’ in the following text books.
Senior Secondary School Physics by P.N. Okeke et al.
New School Physics for Senior Secondary Schools by Anyakoha, M.W.

TOPIC : Expansion of Solid, Effect and Applications of Expansion
CONTENT
 Effect and Application of Thermal Expansion of Solid
 Advantages and Disadvantages of Thermal Expansion of Solid

Effect and Application of Thermal Expansion of Solid
1. When hot water is poured in a glass tumbler, it might crack due to the uneven expansion of the inner wall of the tumbler.
2. The cracking noise of zinc roof during the day and night
3. Thermal expansion of solid is used in the construction of bridges in which one side is fixed and the other is placed on rollers to allow for expansion
4. The stopper of a bottle can be removed due to the expansion of the glass.
5. In the construction of concrete pavement, little spaces are left within the concrete to allow for expansion
6. Gaps are left in the construction of railway tracks to give room for expansion
7. Bimetallic stripes are use in thermostat for controlling or regulating the flow of electric current.
https://youtu.be/6pScZaNz7nY

Advantages and Disadvantages of Thermal Expansion of Solid
Advantages
1. Fire alarm e.g. electric bell
2. The fittings of wheels in rims
3. Bimetallic thermometer
4. Red hot rivet in ship building
5. Bimetallic stripes used in thermometer e.g. electric cooker etc

Disadvantages
1. Cracking of drinking glass when hot liquid poured inside
2. If the balance wheel of a watch expands the time will be fast and if the balance wheel of a watch contrasts the time will be slow
3. Expansion of metal of concrete bridges which can lead to eventual after a long period
4. Sagging of overhead wire due to contraction in winter season
5. Expansion of railway tracks thereby forming distant railway tracks.
6. Bursting of water metal pipes.
https://youtu.be/EnyMoYbJvjc

EVALUTION
1. Mention four effect of thermal expansion of solid
2. Mention four the advantages and disadvantages of thermal expansion of solid
Reading Assignment-www.google.com(click on google search, type “expansion of solid”,click on search) and New School Physics pg 37 - 42

ASSIGNMENT
1. Gaps are left in the construction of railway tracks to give room for …………. (a) contraction (b) evaporation (c) expansion (d) vaporization
2. When hot water is poured in a glass tumbler, it might crack due to the ………… of the inner walls of the tumbler (a) even expansion (b) uneven expansion (c) uneven contraction (d) even contraction
3. The stopper of a bottle can be removed due to the ………… of the glass (a) contraction (b) expansion (c) evaporation (d) none of the above
4. The following are advantages of thermal expansion of solids except (a) bimetallic thermometer (b) fire alarm (c) sagging of overhead wire (d) fitting of wheels in rims
5. If heat is removed from solids they (a) contract (b) evaporate (c) expand (d) none of the above

THEORY
1. Mention four effect of thermal expansion of solid
2. Mention four the advantages and disadvantages of thermal expansion of solid





TOPIC: Scalars and vectors:
Concept of scalars
Concept of vectors
Distinction between scalars and vectors.

CONCEPT OF SCALARS
Scalars are physical quantities that have magnitude but no direction. This means that a scalar quantity has value which is the magnitude but has no direction. E.g, 10km. This 10km could be in any direction since there is no actual direction. The ‘10’ is the value- the magnitude. Therefore, just 10km is a scalar quantity. Scalar quantities are always not directional.
Other examples of scalar quantities include:
Speed
Time
Density
Mass
Distance, etc.


https://youtu.be/V_CJXlgar8Y

CONCEPT OF VECTORS
Vectors are physical quantities that have both magnitude and direction. This means that vectors quantities have values and are always directional. E.g, 10km due North. Here, the value, which is the magnitude, is ‘10’ while the direction is North.
Other examples of vector quantities are:
25km at N60°E
Displacement
Force
Acceleration
Momentum
Impulse
Velocity
Weight, etc.


https://youtu.be/wAs1TIiF7A0

Evaluation:
1. What are vector quantities?
2. List five examples of each of the two types of the physical quantities.




DISTINCTION BETWEEN SCALARS AND VECTORS.

S/N SCALARS VECTORS
1. Scalars are non directional physical quantities. Vectors are directional physical quantities.
2. Always directed towards different directions. Always directed towards a particular direction.
3. E.g, 100km 100km due east.
4. E.g, mass Weight

https://youtu.be/rcDXQ-5H8mk
Their similarities include:
They are both physical quantities;
They both have values, which are the magnitudes.

Evaluation:
1. State three differences between scalars and vectors.
2. State the similarities between them.

GENERAL EVALUATION:
1. What is the difference between 20km and 20km due South?
2. How would you differentiate a scalar from a vector quantity?
3. List five examples of scalar quantities.
4. Mention five physical quantities you consider as vectors and why.
https://youtu.be/sXKiAKn0WCM
ASSIGNMENT:
1. 200inches due east is an example of ---
Displacement
Speed
Acceleration
Distance
2. 20km due east is an example of ---
Scalar quantity
Vector quantity
Fundamental quantity
Basic quantity
3. 500 miles is an example of,..
Displacement
Distance
Force
Speed
4. The following are examples of scalar quantities. Except ---
Time
Density
Velocity
Mass
5. One of the following is a vector quantity.
Force
Distance
Mass
Speed

Essay
Tabulate the below physical quantities into scalars and vectors.
Force, acceleration, speed, velocity, time, mass, weight, distance, momentum, displacement.

READING ASSIGNMENT
Read up the topic: ‘’Work, Energy and Power’’ in the following text books.
Senior Secondary School Physics by P.N. Okeke et al.
New School Physics for Senior Secondary Schools by Anyakoha, M.W.

TOPIC : Expansivity and Its Application – Linear, Area and Volume. Anomalous Expansion of Water. Real and Apparent Expansivity

CONTENT
 Linear Expansivity of Solid
 Area Expansivity of Solid
 Cubic Expansivity of solid and Liquid
 Anomalous Behaviour of Water
https://youtu.be/4UE_cxd7TEw

Linear Expansivity
Linear expansivity of a solid can be defined as increase in length per unit length, per unit degree rise in temperature. It is denoted by (α) and measure in per Kelvin or per degree Celsius.

Mathematical representation


L1 is the original length

L2 is the final length

Ө1 is the initial temperature

Ө2 is the final temperature


EXPANSION IN SOLID
N.B.
▲L = L2 – L1

▲Ө = Ө2 - Ө1

1.A brass rod is 2m long at a certain temperature. What will be the length for a temperature rise of 100K , if the linear expansivity of brass 18 x 10-6K-1
SOLUTION
L1 = 2m, L2 =?, ▲Ө = 100K, α = 18x1o-6k-1

L2 = L1 (1 + α▲Ө)

L2 = 2 (1 + (18 X 10-6 X 100)

= 2(1 + 0.00018)

= 2 (1.OOO18)

= 2.0036m

Area Expansivity
The area/superficial expansivity is the increase in area of per unit area per degree rise in temperature. It is donated by (β) and measured in per Kelvin and per 8C

https://youtu.be/Hr4g2EzE3Tc

EVALUATION
1. A brass rod is 2m long at a certain temperature. What will be its length for a temperature rise of 90K , if the linear expansivity of brass is 1.8 x 10-6K-1
2. Prove that A2 = A1 ( 1 + β ▲ Ө)


Volume/Cubic Expansivity
It is denoted by (Y). It is the increase in volume per unit volume per degree rise in temperature


Real and Apparent Cubic Expansivity of Water
Real or absolute cubic expansivity (Yr ).
The real / absolute of the liquid is the increase in volume by unit volume per degree rise in temperature

Apparent Cubic Expansivity (Ya )
The apparent cubic expansivity is the increase in volume per unit rise when heated in an expansible vessel.
Yr = Ya + Y

Anomalous Behaviour of Water
Most liquid except water expand when heated. This abnormal behaviour of water is what is refer to as anomalous expansion of water. When water is heated from 0ºC, it contracts until it reaches 4ºC and beyond this point, water expand normally. The anomalous expansion of water takes place between 0ºC and 4ºC.
https://youtu.be/ziWegVVAnCI

https://youtu.be/LkzmVn3alwY

EVALUATION
1. With the aid of a diagram, explain the anomalous behaviour of water
2. Describe an experiment to determine the apparent cubic expansivity of a liquid
Reading Assignment : New School Physics pg 38 – 40,43 - 46

ASSIGNMENT
1. The anomalous expansion of water takes place between/at ………………..(a) 1ºC and 4ºC
(b) 0ºC and 4ºC (c) 4ºC and 25ºC (d) all temperature

2. The SI unit of linear expansivity is ……… (a) per celcius (b) per fehreinheit (c) per Kelvin (d) per Joules

3. If the linear expansivity of a solid is 1.8 X 10-6 k-1, the area expansivity will be

(a)0.9 X 10-6 (b) 3.6 X 10-6 (c) 1.8 X 10-6 (d) 5.4 X 10-6

4. A metal of length 15.01m is heated until its temperature rises by 60ºC. If its new length is 15.05, calculate its linear expansivity
(a) 0.0004/K (b) 0.00004/K (c) 0.004/K (d) 0.04/K

5. The increase in volume of 10cm3 of mercury when the temperature rises by 100ºC is 0.182cm3. What is the cubic expansivity of mercury (a) 0.000182/K (b) 0.0000182/K (c) 0.000187/K (d) 0.000178/K

THEORY
1. Explain the anomalous behavior of water
2. If a cube metal box made of iron of side 2cm is to be used for construction, and the expected temperature difference is 900C. What will be the expected change in volume of the cube box if the linear expansivity of iron is 1.25 X 10-5.




TOPIC: WORK, ENERGY AND POWER
CONTENT:
1. Concept of work, energy and power
2. Interchangeability of work and energy
3. Determination of work, energy and power

Definition of work, energy and power.
Work done in Physics is simply defined as the product of force and distance in the direction of the force. If work done is w, distance covered is s and force is f, then mathematically,
Work done = force x distance
W = f x s
the S.I unit of work done is Joules ( J ). Since unit of force ‘f’ is Newton (N), unit of distance ‘s’ is metre, the unit of work done is also Newton-Metre (Nm). Other units are kilojoules and mega joules. Note: If no distance is covered, work done is zero. Work done is a scalar quantity.
Energy is the ability or capacity to do work. Its unit is Joules
Power can be defined in a number of ways 1. Power is the time rate at which work is done. 2. Power is energy expended with time. 3. Power is work done in a given time interval. Its unit is watt. Larger units are horse power (hp), kilowatt (kw) and megawatt (mw).
Mathematically.

Power (P) = (work done (w)or energy expended )/(time taken (t)

= w/t

= (f X s)/t

= f x v
Where f is force and v is velocity which is distance / time i.e s / t.



That means power can also be defined as the product of force and velocity. The instrument for measuring power is watt-metre.
https://youtu.be/zVRH9d5PW8g

https://youtu.be/zaceSCDATjg

Interchangeability of work and energy
Energy and work can be used interchangeably because they are almost the same thing. They have the same unit which is Joule. For example, if someone has energy, it means he can do some work and if someone can do some work, it means he has some energy. Thus work and energy cannot be separated.
https://youtu.be/_MR1Dp8-F8w

Evaluation
Define work, energy and power. State the unit of each
Can energy and work be used interchangeably? explain



Determination of work, energy and power
When calculating work done and power, we start by first stating the formula as illustrated in the following examples below.
https://youtu.be/8jC8AzyuiwM

Example 1
A body of weight 300N climbs to the top of a hill of height 20m. What is the work done by the body against the force of gravity?

Solution
Force f = 300N, distance s = 20m
Work done = force x distance
= f x s
= 300 x 20 = 6000J

Example 2.
An object of mass 12kg is held at a height of 10m above the ground for 15 minutes. Calculate the work done within this period.

Solution
Since the body is not falling freely under gravity, acceleration due to gravity is zero. Hence work done is also zero.

Example 3
A bag of rice of mass 50kg was pushed through a distance of 5m for 10seconds. Calculate the work done.(g = 10ms-2)

Solution
m = 50.0kg, g = 10ms-2, s = 5m and t = 10 seconds.
Work done = force x distance
= f x s
= mg x s. Since f = mg
= 50 x 10 x 5
= 2500J
Notice that we did not use the value 10 because it is irrelevant since the definition of work done does not involve time.

Example 4
Calculate the power of a pump which lifts 1000kg of water through a vertical height of 2m in 10 seconds. ( g = 10ms-2)

Solution
Mass (m) = 1000kg, distance (s) = 2m, time (t) = 10s

Power = Work done/ Time taken

= force x distance/Time

= m x g x s/ T

= 1000 x 10 x 2/10

= 2000W


Example 5
An engine develops a power of 750W while moving a car at constant velocity of 3ms-s. Calculate the force exerted on the car by the engine.
Solution
Power = 750W, velocity = 3m/s, f = ?
Power = force x velocity

Force = power/Velocity

= 750 / 3 = 250N

https://youtu.be/t9gRaBOQMGU

Evaluation
Differentiate between work done and power
What other unit is used in measuring work done?
A girl applied a force of 20N on an object for 5s. if the object remains stationary, calculate the work done
A boy lifted up a bag of yam of weight 5N through a height of 2m in 10s. Calculate his power.

Assignment
Reading assignment: read on types of energy and the law of conservation of energy

A boy of mass 50kg runs a set of step of steps of total height 10cm. calculate the work done (take g = 10ms-2)
A 70kg man ascends a flight of stairs of height 4m in 7 seconds. Calculate the power expended by the man
A 40kg girl climbs up a stair and expends energy at the rate of 50W. calculate the time taken for her to reach a height of 20m

TOPIC : Heat Transfer – Conduction, Convection, Radiation and Their Applications
CONTENT
 Conduction
 Convection
 Radiation
 Thermo Flask
Heat can be transferred by conduction, convection or radiation

CONDUCTION
This is the process of transfer of heat through a material by vibration of the molecules fixed in position. N.B. Metals that allow heat to pass through them are said to be good conductors of heat. Though all metals are classified as good conductors, they differ in an ability to conduct heat. Non metal (wood / plastic) are bad conductors that does not allow heat to pass through it. Thermal conductivity is simply the ability of a metal to conduct heat.


PRACTICAL CONDUCTION OF HEAT
1. Kettle, pans and other utensils made of metals are provided with wooden or ebonite utensils so that heat from to utensils is not conducted
2. house old source pans are made of metals because metals are good conductors of heat and electricity
3. Thick brick walls are used in the construction of storage rooms. Bricks are bad conductors of heat, so it will not allow heat to enter the storage room.
4. A stone floor feels cold to the feet than a rug or a carpet on the same floor feels warm



CONVECTION
Convection is the process by which heat energy is transferred in a fluid (liquid or gas) by actual movement of the heated fluid. The direction of the motion of a filter paper indicates the circulation of heated water. Circulation of a liquid is called CONVECTION CURRENT.


RADIATION
Radiation is the process by which heat is transferred or conveyed from one place / point to another without heating the interview medium. In radiation molecules are not involved, it differs from another method because it does not require a medium for heat to be transferred. Heat from the sun reaches us by this method. The energy given out as radiant heat is known as RADIANT ENERGY. This energy displace electrical and magnetic properties and it said to be electromagnetic radiation and the name is INFARED.


RADIATION CAN BE DETECTED BY
1. Radiometer
2. Thermo pile
3. Leslie cube
Dark surface are good absorber of heat and poor he meter of radiation. Highly polished surface are good he meter of radiation and poor he meter of heat.

APPLICATION OF RADIATION
1. It is not advisable to wear a dark shirt in the tropical sun
2. Roofs of factories are coated with aluminium paint.
3. Shinning roofs and outside walls are painted with light colour in hot climate to keep the house cool.
Cooking utensils are darkening at the bottom and polished in the upper surface. The blacking surface will allow the heat while the silver surface won’t allow the heat to go out.
https://youtu.be/9joLYfayee8

Thermos Flask
A thermos flask is used to keep the temperature of its content constant. The essential feature of a thermos flask are as follows :
1. Cork stopper – Prevent heat loss by conduction, conduction and Evaporation
2. Vacuum in the double wall – Reduce heat loss or gain by conduction and convection
3. Silvered wall surface – Minimise heat loss by radiation
4. Cork support – Prevent heat loss by conduction
Thermos flask is also known as vacuum flask.
https://youtu.be/EZmTo1SVYZo

EVALUATION
1. Define the following terms (a) conduction (b) Convection (c) Radiation
2. State two application of radiation.
3. Define the following terms (a) Conduction (b) Convection (c) Radiation
4. With the aid of a diagram, explain how the construction of a thermos flask minimizes heat exchange with the surrounding

Reading Assignment : New School Physics pg 46 - 53

ASSIGNMENT
1. The silver surface of a thermos flask minimizes heat loss by (a) conduction (b) radiation (c) convection (d) evaporation
2. Is it advisable to wear a dark shirt in the tropical sun? (a) yes it is (b) No it is not (c) Cannot say (d) All of the above
3. The following are good conductors of heat except (a) steel (b) aluminium (c) copper (d) wool
4. The thermal conductivity of copper is greater than lead (a) true (b) false (c) cannot say (d) none of the above
5. A stone floor feels warm to the feet but a rug or a carpet on the same floor feels cold (a) true (b) false (c) cannot say (d) none of the above
THEORY
1. Define the following terms (a) Conduction (b) Convection (c) Radiation
2. With the aid of a diagram, explain how the construction of a thermos flask minimizes heat exchange with the surrounding






TOPIC: WORK, ENERGY AND POWER (CONT’D)
CONTENTS
1. Work done in a force field
2. Types of energy
3. Law of conservation of energy

Work done in a force field
Every object on the earth’s surface is under the influence of the force of gravity. This force pulls the object towards its centre. The earth’s gravitational field is an example of force field. If a body is to be lifted vertically upwards, work has to be done against this force of gravity. The work done is given as
Work done = force x distance
= m x g x h
Where m = mass of the body in kilogram, g = acceleration due to gravity and h is height in metres. If on the other hand, the body falls freely from a vertical height h to the ground, the work done is also mgh.
https://youtu.be/viOoooQNP6I

Example 1
A stone of mass 10kg falls from a height of 2.0m. Calculate the work done. (take g = 10ms2)
Solution
Mass (m) = 10kg, height (h) = 2.0m
Work done = mgh
= 10 x 10 x 2 = 200J



Types of energy
Energy exists in various forms some of which are;
1. Mechanical energy
2. Chemical energy
3. Solar energy
4. Heat energy
5. Sound energy
6. Electrical energy
7. Nuclear energy




Mechanical energy
Kinetic energy and potential energy constitutes mechanical energy. Kinetic energy is the energy a body possesses as a result of its motion. Potential energy on the other hand, is the energy possessed by a body because of its position. A body can also possess potential energy as a result of its nature. For example, an elastic material when stretched stores up energy (potential energy) which is given as ½ k e2 where k is what we call the elastic constant and e is extension in metres. Another form of potential energy is chemical potential energy which is energy stored up in a substance because of its chemical composition. Examples are; energy in the food we eat, electrolytes in cells or batteries.
Mathematically, Kinetic energy K. E = ½( mv2). m is mass in kilogram, v is velocity in m/s.
If a body is raised to a height h, its potential energy is given as
P.E = mgh. Where m is mass in kilogram, h is height in metres and g is acceleration due to gravity.

Example 2
A body of mass 100kg is released from a height of 200m. With what energy does the body strike the ground? (g = 10 m/s2)
Solution
Gravitational potential energy is given as P.E = mgh = 100 x 10 x 200 = 200,000J

Example 3
A stone of mass 50.0kg is moving with a velocity of 20 m/s. calculate the kinetic energy
Solution
mass = 50.0kg, velocity = 20 m/s
K. E = ½ mv2 = ½ x 50.0 x 20.0 = 500J

https://youtu.be/jhKejoBqiYc

Evaluation
1. Differentiate between potential energy and kinetic energy
2. What is the formula for calculating kinetic energy and potential energy


Law of conservation of energy
https://youtu.be/Vx0yAS2u8gI
Energy as we have treated earlier exists in various forms. Although energy can be converted from one form to the other, the total energy remains conserved. This is the law of conservation of energy. It states that energy can neither be created nor destroyed but can be converted from one form to the other. This law can be illustrated by mechanical systems as shown in the figures below.


Fig. 1 illustrates the energy transformation that takes place in a simple pendulum. Point B is the mean position or rest position while points A and C are the extreme points of oscillation of the pendulum. At point (A), the velocity of the bob reduces to zero and the height (h) of the bob from the horizontal ground is maximum. Hence Kinetic Energy (K.E) of the bob is zero and potential energy is maximum. The same thing applies to point (C). At point (B), the speed or velocity of the bob as it moves from (A) to (B) is maximum, while the height (h) of the bob reduces to zero. Therefore at this point, the potential energy is zero and the kinetic energy is maximum. As the bob moves from point (B) to points (A) and (c), its velocity and kinetic energy reduces and the kinetic energy is totally converted to potential energy at the two extreme points. As the bob moves from the two extreme points (A) and (C) to (B), the velocity increases and is maximum at point (B) and the potential energy is totally converted to kinetic energy.
In fig. 2, as the body moves from the horizontal ground C to A, its velocity reduces and at point A, at height h, where the body is stationary, the velocity v is zero. Consequently its kinetic energy is zero but the potential energy is maximum. As the body drops to the ground, its velocity increases and the vertical height h reduces to zero. Therefore, potential energy just before it touches the ground is zero and the body has maximum kinetic energy. At point B, the body possesses both Kinetic energy and potential energy. From the two illustrations we see that although the energy changes from kinetic to potential energy and vice versa, the total energy of the system is conserved or remains unchanged.
https://youtu.be/gW9fSb9cZnc

Evaluation
1. List eight forms of energy you know
2. State the law of conservation of energy and apply it to any mechanical system

Assignment
1. Reading assignment: Read on heat energy temperature and the kinetic theory of matter.
2. Give two sources each of the following forms of energy; kinetic energy, heat energy, electrical energy, chemical energy, solar energy
3. If the maximum speed of a pendulum bob is 4.5 m/s at the lowest point O, calculate the height h of the pendulum bob above O where its velocity is zero
4. (a) Define the following terms (i) Work (ii) Energy (iii) kinetic energy
(iv) potential energy.
(b) State two differences and two similarities between power and energy.
(c) Calculate the power of a pump which can lift 100kg of water through a
vertical height of 5m in 20secs ( g = 10m/s2 ).
(d) A ball of mass 8kg falls from rest from a height of 100m. Neglecting air
resistance, calculate its kinetic energy after falling a distance of 30m.
(take g as 10m/s2).
5. A drum of mass 1000kg is rolled into the deck of a lorry 1.5m above a
horizontal floor using a plank 4m long. calculate the work done against
gravity during the process. ( g = 10m/s2 ).
A ball of mass 1kg is dropped from a height of 5m and bounces to a height
of 10m. Calculate (i) its kinetic energy just before impact.
(ii) its initial bouncing velocity and kinetic energy.
6. A stone of mass 1.0kg is thrown vertically upwards with a velocity of
10m/s.
Find (i) the potential energy at the greatest height h and the value of h.
(ii) the kinetic energy on reaching the ground again ( g = 10m/s2).

Objectives
1. Power is defined as the
A. capacity to exert a force
B. product of force and time
C. product of force and distance
D. energy expended per unit
time.

2. What is the unit equivalent of joules?
A. Nm B. Nm2
C. kgm/s D. kgm/s2

What is the unit equivalent of watt?
A. Nm/s B. Nm
C. kg/m D. kg/m

3. Which of the following sources has the same unit as energy?
A. Power B. Work
C. Force D. Momentum

4. Which of the following sources of energy is renewable?
A. sun B. Petroleum
C. Coal D. Uranium

4. Which of the following statements correctly defines quantitatively, the work done by a force? The product of the force and the distance moved
A. parallel to the line of action
of the force from a reference point.
B. perpendicular to the line of
action of the force from a
reference point.
C. on a line through the
reference point.
D. by the object.

5. The mass on a loaded spiral spring oscillates vertically between two extreme positions P
and R equidistant from the
equilibrium position Q. Which of
the following statements about
the system is not correct?
A. The momentum of the mass
is maximum at Q.
B. The elastic potential energy
of the spring is maximum at Q.
C. The kinetic energy of the
mass is maximum at P.
D. The total energy of the
system is always constant.

6. A stone of mass 0.5kg is dropped
from a height of 12m. Calulate its
maximum kinetic energy.
( g = 10m/s2)
A. 3.0J B. 6.0J
C. 30.0J D. 60.0J
7. The diagram below shows the
position of a simple pendulum
set in motion. At which of the
positions does the pendulum
have maximum kinetic energy?
A. 5 B. 4
C. 3 D. 2 and 6


8. A 70 kg man ascends a flight of
stairs of height 4m in 7s. The
power expended by the man is
A. 40W B. 100W
C. 280W D. 400W


9. A pump lifts water into an
overhead tank at a height of 12m
at the rate of 5kg/s. The power of
the pump is
A. 60W B. 600W
C. 720W D. 1200W

10 A 40kg girl climbing a flight of
stairs expends energy at the rate
of 50W. The time taken for her to
reach a height of 20m is
A. 16s B. 32s
C. 80s D. 160s

11. A boy of weight 300N climbs to
the top of a hill of height 20m.
the work done by the boy against
the force of gravity is
A. 6000J B. 600J
C. 320J D. 15J

12. Under which of the following
conditions is work done
A. A man supports a heavy
Load above his head with his hands
B. A woman holds a pot of
water
C. A boy climbs unto a table.
D. A man pushes against a
stationary petrol tanker.

13. At what height above the ground
must a body of mass 10kg be
situated in order to have
potential energy equal in value
to the kinetic energy possessed
by another body of mass 10kg
moving with a velocity of
10m/s?
A. 5m B. 10m
C. 100m D. 500m

14. The time taken to complete one
revolution is…..
A. period B. frequency
C. velocity D. speed

15. The number of oscillations per
second is known as
A. period B. frequency
C. velocity D. speed.

TOPIC : ELECTRIC CHARGES→ Production, Types, Distribution and Storage
CONTENT:
 Production of Charges
 Types of Charges
 Distribution of Charges
 Storage of Charges
 Production of Charges
https://youtu.be/TFlVWf8JX4A
If a plastic pen is rub vigorously on the hair or on a coat and it is hold near a very small piece of paper, the paper will be attracted by the pen. Some substances are found to poses the ability to attract light objects once they are rubbed. The light object as well as the rubbed material are said to be charged or electrified with static electricity.
https://youtube.com/shorts/nvnUFOloUnQ?feature=share

Types of Charges
There are two types of charges- positive and negative charges. An ebonite rod rubbed with fur has a negative charge, but a glass rod rubbed with silk has a positive charge.
The fundamental law of static electricity or electrostatic states that like charges repel will unlike charges attract.
https://youtu.be/2aip8PCv9qE

Distribution of Charges
Charges are unusually concentrated at places where the surface is sharply curved. The charge density i.e charge per unit area is highest at the sharpest point of the conductor.

Storage of Charges
The electrophorus is a device for transferring and storing charges. It produces electric charges by electrostatic induction. Another device for the storage of electric charges is the capacitor
https://youtu.be/z6CVc_9Xreg

EVALUATION
1. State the fundamental law of electrostatic
2. What is electrostatic
3. With the aid of a diagram, explain charge distribution
4. Name two devices that can store charge

Reading Assignment : New School Physics pg 56 – 58, 63 - 65

ASSIGNMENT
1. Electophorus and capacitor can store charges (a) true (b) false (c) cannot say (d) none of the above
2. When an ebonite rod is rub with fur, the fur becomes (a) positively charge (b) negatively charge (c) neutral (d) none of the above
3. The ebonite rod in question 2 becomes (a) positively charge (b) negatively charge (c) neutral (d) none of the above
4. Like charges (a) attract (b) repel (c) disappear (d) evaporate
5. Charges are unusually concentrated at places where the surface is …………. (a) straight (b) sharply curved (c) oval in shape (d) none of the above

THEORY
1. State the fundamental law of electrostatic
2. What is electrostatic




TOPIC: Heat Energy
CONTENTS
1. Concept of heat and temperature
2. The kinetic theory of matter
3. Effects of heat on substances ( expansion, vaporization)

Concept of heat and temperaturee
Heat is a form of energy that moves from one point to the other due to temperature difference. When you dip one end of an iron rod into fire and hold the other end with your hand, this other end soon becomes hot because energy has flowed from the point dipped into the fire to this other end. This energy flow is what is known as heat. Temperature is a measure of how cold or hot a body is.
https://youtu.be/LL54E5CzQ-A

Differences between heat and temperature
Heat ----------------------------------------------Temperature
It is a form of energy ---- It is the degree of hotness or coldness of a body
It is measured in joules ---- It is measured in Kelvin
it is not determined directly by an instrument ----it is directly determined by a thermometer
it is a derived quantity ---- It is a fundamental quantity




The kinetic theory of matter
The kinetic theory of matter states that
1. Matter is made up of atoms and molecules
2. The molecules are in a state of constant random motion
3. They possess kinetic energy because of their motion
4. The kinetic energy of the molecules is directly proportional to the temperature of the body.

Evaluation.
1. Define temperature and state its unit
2. State three assumptions of the kinetic theory of matter


Effects of heat on substances ( expansion, vaporization)
When heat is applied to a substance, it can lead to the following changes
1. Chemical changes
2. Temperature changes
3. Expansion/contraction
4. Change of state (melting, vaporization, sublimation)
5. Change in pressure
6. Thermionic emission

Thermal expansion
Most solid substances expand when heated. The rate of expansion varies from solid to solid. Expansion is more pronounced in gases followed by liquids and least in solids. A substance whether solid, liquid or gaseous consists of molecules. When the substance is heated, the molecules gain kinetic energy and move faster and hence the molecules take up more space in the substance. This leads to expansion.

Ball and ring experiment
An experiment can be carried out to demonstrate expansion of a solid.
Apparatus: Bunsen burner, ball and ring apparatus



Procedure: Allow the metal ball to pass through the ring. Heat the metal ball for some time in the Bunsen burner and make it pass through the same ring. The metal ball will no longer pass through the same ring it passed through earlier as a result of expansion. When allowed to cool down for some time and allowed to pass through the ring once more, it will pass through because it has contracted and regained its original size.
Using kinetic theory to explain temperature of a body
https://youtu.be/GgrnhHMqZDY

According to the kinetic theory of matter, the average kinetic energy of the molecules is directly proportional to the temperature. This means that as the kinetic energy of the molecules increases, the temperature also increases. When a body is subjected to heat, the velocities of the molecules increases and hence they gain more kinetic energy this of course will lead to increase in the temperature of the body. On the other hand, if we reduce or lower the heat, the velocities of the molecules will decrease leading to a decrease in the kinetic energy of the molecules. Hence the temperature falls or reduces.

Evaluation
1. Give three differences between heat and temperature
2. Explain the phenomenon of expansion using the kinetic theory of matter
3. Give four effects of heat on a substance

Assignment
1. Give three applications of expansion/contraction
2. What is a bimetallic strip? Give two applications of a bimetallic strip
3. Explain how a thermostat regulates the temperature of an electric iron
4. Mention three solids that undergoes sublimation

TOPIC: THERMAL EXPANSIVITY

CONTENT: 1. Linear expansion, Coefficient of linear expansivity
2. Experimental determination of linear expansivity , Area expansivity
3. Cubic expansivity, Experiment to determine the apparent cubic expansivity.
4. Applications of expansion

Linear expansion, Coefficient of linear expansivity

TYPES OF EXPANSION:
I. Linear expansion
2. Area or Superficial Expansion
3. Volume or cubic Expansion

LINEAR EXPANSION: linear expansion is expansion in length of a body. Different solids expand at different rates, this is because they have different coefficient of linear expansivity.
https://youtu.be/LYt4IpuKW3M

COEFFICIENT OF LINEAR EXPANSIVITY (α)
It is defined as increase in length per unit length per degree rise in temperature. The unit is per Kelvin or 1/k or k – 1



Question 1.
What is meant by the statement, the linear expansivity of copper is 0.000017/k.
Solution:
It means that the increase in length per unit length per degree rise in temperature of copper is 0.000017m.

Question 2:
A brass is 2 meters long at a certain temperature. What is its length for a temperature rise of 100k, if expansivity of brass is 1.8 x 10-5/k
Solution:


Question 3:
A metal of length 15.01m is heated until its temperature rises to 60ºC. If its new length is 15.05m, calculate its linear expansivity.

Solution:



EVALUATION:
I. What is meant by the statement that the linear expansivity of copper is 0.000017/k.
2. Steel bars each of length 3m at 29ºc are to be used for constructing a rail line. If the linear expansivity of steel is 1.0 x 10-5/k. Calculate the safety gap that must be kept between successive bars, If the highest temperature expected is 40ºc.


1. Experiment to determine the linear expansivity of a metal block.
2. Area expansivity

1. Experiment to determine the linear expansivity of a metal block.



Aim: Experiment to determine the linear expansivity of a metal block
Apparatus: Thermometer, Micrometer screw guage, steam jacket, metal rod, meter rule
Method:
i. Measure the length of the metal rod (L1).

ii. Insert the metal rod in the steam jacket and take the initial temperature of the metal rod with thermometer (θ1).

iii. Screw the micro-meter to touch the end of the rod and take the reading of micro-meter (xi).

iv. Unscrew micro meter to make room for expansion of metal rod.

v. Introduce steam into the steam jacket for several minutes then the metal rod will expand.

vi. Screw the micrometer screw guage to touch the end of the metal rod again and take the reading again (x2).

vii. Record the final temperature (θ2).

https://youtu.be/-5E759UfTKY

Calculation:


Conclusion: Since all parameters are known α can be calculated.

https://youtu.be/ZTHKDG3t9So

2. Area or Superficial expansivity(β)
It is defined as the increase in area per unit area per degree rise in temperature


Relationship between Linear expansivity and Area expansivity:
Β = 2α

Question 1: A metal cube of cross sectional area 3.45m2 at 0ºc is heated at a temperature rise of 70k, when the final length of the cube is 3m. Find the:
i. coefficient of superficial expansivity.
ii. coefficient of linear expansivity.
Solution:


EVALUATION:
1. The linear expansivity of a metal is 0.000019 per k. What will the area of 400mm2 be if its temperature is raised by 10ºC.


Cubic expansivity, Experiment to determine the apparent cubic expansivity.

Cubic or volume expansivity(γ)
It is defined as the increase in volume per unit volume per degree rise in temperature


Relationship between Linear expansivity and Cubic expansivity:
γ = 3α

Question 2: The increase in the volume of 10cm3 of mercury when the temperature rises by 100ºc is 0.182cm3. What is cubic expansivity of mercury.




EXPANSION IN LIQUIDS:
Expansion in liquid is complicated by the expansion of the container because while the liquid expands the container equally expands. So it is important to differentiate between real and apparent cubic expansivity.

REAL OR ABSOLUTE CUBIC EXPANSIVITY (γr): It is defined as the increase in volume per unit volume per degree rise in temperature.

APPARENT CUBIC EXPANSIVITY (γa): It is defined as the increase in volume per unit volume per degree rise in temperature when the liquid is heated in an expansible vessel.

γr = γa+ γ

γr = Real or cubic expansivity of liquid

γa = Apparent cubic expansivity of liquid

γ = cubic expansivity of the container


QUESTION 3:
A cube with side 100cm at 0ºC is heated to 100ºC. If the side becomes 101cm long find,
a. The linear expansivity
b. The cubic expansivity

SOLUTION:




DETERMINATION OF THE APPARENT CUBIC EXPANSIVITY OF A LIQUID.



APPARATUS: Thermometer, Density bottle, Retort stand, Water, Source of heat, Beaker, Beam balance, Liquid, Stirrer.
METHOD:
i. Dry the density bottle and weigh it (M).

ii. Fill the density bottle with the liquid that the apparent cubic expansivity is required and weigh it (M1)

iii. Immerse the density bottle into a beaker of water and suspend with a thread on the clamp of the retort stand.

iv. Take the original temperature of the water in the beaker (θ1).

v. Heat the set up gently until the water boils.

vi. Some liquid are expelled through the orifice of the bottle cover, the heating continues until no liquid is seen expelled again.

vii. The final temperature of water is taken(θ2)

viii. The density bottle is removed and wiped dry and re-weighed(M2).

https://youtu.be/qXP71ivOJjQ
https://youtu.be/ziWegVVAnCI

CALCULATION:
Mass of empty density bottle = M

Mass of density bottle + liquid = M1

Original temperature of water = θ1

Final temperature of liquid = θ2

Mass of remaining liquid + density bottle = M2



CONCLUSION:
Since all the parameters are known, apparent cubic expansivity γa can be calculated.

EVALUATION:
1. Differentiate between Real cubic expansivity and Apparent cubic expansivity.
2. A glass bottle full of mercury has mass 500g on being heated through 35ºC, 2.43g of mercury was expelled.

Calculate the mass of mercury remaining in the bottle ( cubic expansivity of mercury is 1.8 x 10-4/k and

linear expansivity of glass is 8.0 x 10-6/k)


Applications of Expansion

(A) ADVANTAGES OF EXPANSION:
1. The use of the bimetallic strip in:
a. Fire alarm
b. Bi-metallic thermometer
c. Electric pressing iron

2. Red hot rivet used in ship
3. Removal of tight glass stopper
4. Fitting of wheels in rims
https://youtu.be/6pScZaNz7nY

Bi-metallic strip:
It consists of two different metals joined together. They expand at different rates when heated e.g brass and iron.


a. ELECTRIC FIRE ALARM:

When a fire breaks out in a building, the resulting heat causes the bi-metallic strip to bend towards the contact, thus completing the circuit. This causes the bell to ring out a fire alarm.

b. BI-METALLIC THERMOMETER

It consists of a coiled bi-metallic strip which expands outwards when heated. As this
happens, the pointer moves along the scale and the reading on the scale is taken as the
temperature.

c. ELECTRIC PRESSING IRON:
It has a device known as Thermostat, it is made of bi-metallic strip and it is used to regulate
the temperature of the pressing iron, Gas cooker, Refrigerator.


https://youtu.be/2T4TV4xOZWg

MODE OF OPERATION OF PRESSING IRON
When the current is switched on, current flows through the circuit and the bi-metallic strip
expands and bends away from the contact point thereby switching off the flow of current.
The pressing iron cools down and contact is re-made and current flows again and the process
continues. This make-and-break device regulates the temperature of a pressing iron.

2. RED-HOT RIVET USED IN SHIP:
Steel plates and girders which are used in ship building and other constructional works are usually riveted together.

3. FITTING OF WHEELS IN RIMS:
The large driving wheels of locomotive are fixed with steel tyre which are renewed from time to time as they wear out. In order to ensure a tight fitting, the tyre is made slightly smaller in diameter than the wheel. The tyre contracts on cooling thus ensuring tight fitting.

4. REMOVAL OF TIGHT GLASS STOPPER:
A tight glass stopper can be removed by standing the bottle in hot water. The glass bottle expands and the stopper becomes loose.

(B) DISADVANTAGES OF EXPANSION:
1. Expansion of metal on steel bridges/galvanized iron sheets: Cracking sounds are heard when galvanized iron sheets used in the roof of buildings are being heated. This is due to the expansion of sheet when heated. Bridges made of steel equally expand during hot weather.
2. Cracking of glass cup when hot water is poured into it: When hot water is poured into the glass tumbler, it often cracks due to uneven expansion of the interior walls and exterior walls of the glass cup.
3. Expansion of balance wheel of a wrist watch. This makes the watch to give wrong reading
4. Sagging of overhead wires: Telegraph wires when laid in hot weather are allowed to sag so that in cold weather they can contract without snapping.
5. Expansion of railway lines: Gaps are left between rails in railway lines to allow for free expansion and contraction of rails, without the gaps, there would be buckling of rails.


GENERAL EVALUATION:
I. Explain four advantages of expansion in solids.
2. Explain three disadvantages of expansion in solids

ASSIGNMENT:
:
1. The unit of linear expansivity is
A. m/k B. m/k C. k D. K – 1

2. A copper rod is 3m long at a certain temperature. Calculate its length for a temperature rise of 100k if the linear expansivity of copper is

17 x 10-6 1/k.
A. 3.0051 B. 3.0017
C. 3.5100 D. 3.0510

3. Calculate the change in length of a wire of length 35m which is heated from a temperature of 100c to 50ºc.

[ linear expansivity of the material of the wire = 2.0 x 10-6 1/k].

A. 2.8 x 10-3 B. 2.8 x 10-6 C. 2.8 x 10-5 D. 2.8 x 10-4

4. Steel bars each of length 3m at 28ºc are to be used for constructing a rail line. If the linear expansivity of steel is 1.0 X 10-5/k, what is the safety gap that must be left between successive bars if the highest temperature expected is 40ºc?

A. 1.2 X 10-1cm B. 7.2 X 10-2cm C. 6.0 X 10-2cm D. 3.6 X 10-2cm

5. A solid material of volume 100cm3 is heated through a temperature difference of 40ºc.

Calculate the increase in the volume of the material if its linear expansivity is 2.0 x 10-6/k.

A. 2.4 X 10-2cm3 B. 1.6 X 10-2cm3 C. 8.0 X 10-3cm3 D. 5.0 X 10-6cm3

ESSAY
1. a. What is meant by the statement: ‘The linear expansivity of zinc is 2.6 x 10-5k-1?
b. Describe an experiment to determine the linear expansivity of a zinc rod.
c. State one advantage and two disadvantage of thermal expansion of solids.[Neco 2000]
d. An iron rod is 1.58m long at 0ºc.What must be the length of a brass rod at 0ºc if the difference between the lengths of the two rods is to remain the same at all temperatures.

[ linear expansivity of iron = 1.2 x 10-5k-1, linear expansivity of brass = 1.9 x 10-5/k].

2a A density glass bottle contains 44.25g of a liquid at 0ºc and 42.02g at 50ºc.Calculate the real cubic expansivity of the liquid

[ linear expansivity of glass= 1.0 x 10-5/k].

b. The increase in the volume of 10cm3 of mercury when the temperature rises by 100ºc is 0.182cm3. What is the cubic expansivity of mercury?
c. A glass bottle full of mercury has mass 500g on being heated through 35ºc, 2.43g of mercury is expelled. Calculate the mass of the mercury remaining in the bottle

( cubic expansivity of mercury is 1.8 x 10-4/k, linear expansivity of glass is 8.0 x 10-6/k).

PRE-READING ASSIGNMENT
Read the three modes of heat transfer from your physics Text book

ACTIVITY
Using molecular theory explain conduction of heat

REFERENCE TEXTS:
1. New School Physics for senior secondary schools by M.W. Anyakoha
2. Senior secondary physics by P.N Okeke, F.N Okeke, S.F. Akande

TOPIC: TRANSFER OF HEAT

CONTENT: 1. Meaning, molecular explanation of conduction and applications of conductors
2. Meaning, molecular explanation. and application of convection
3. Radiation, Emission and radiation by different surfaces, The Thermos flask.

Meaning, molecular explanation of conduction and applications of conductors
Conduction of heat is the process by which heat is passed along a material from molecule to molecule, the heated particles remaining in position. Most metals are good conductors but their thermal conductivities differ from metal to metal. Experiment performed to compare the conductivity of solid showed the copper is a better conductor than brass, followed by iron, lead.

Kinetic molecular theory explanation of conduction


Heat is passed along the molecules of the material fixed in position, from molecule A to molecule B by mutual vibration and energy is transferred along until it gets to molecule Z.

Conduction in liquids:
Liquids are poor conductors of heat except mercury and other molten metals. Experiment demonstrated below shows that water is a poor conductor of heat.
Experiment to show that water is a poor conductor of heat.




Aim: To show that water is a bad conductor of heat.
Apparatus: water, test tube, ice-block, Bunsen burner and wire guaze.
Method: i. Wrap the ice block with wire guaze to prevent the ice from floating in water, and drop in the water in the test tube.
ii. Heat the water near the top of the water with the Bunsen burner.
Observation: It is observed that while the water was boiling on top, the ice at the bottom did not melt
Conclusion: The ice did not melt because water is poor conductor of heat and was not able to conduct the heat to the ice.
https://youtu.be/L3zN0wYWJgQ

Applications of conductors and insulators
1. Cooking utensils: Bad conductors of heat are used as handles while the cooking pots are made of metals which are good conductors of heat.
2. Lagging: Insulators are often used as lagging materials in hot water pipes, stem boilers, hot water storage tanks and ovens to prevent them from freezing or getting colder.
3. Warmth: Woollen sweaters keep us warm during winter or cold weather to prevent conduction of heat from the body.
4. Double walls: Houses built with double walls with space in between them have air trapped in the spaces that act as insulators, thus, keeping the house warm.
https://youtu.be/jeDFc42YZc4

EVALUATION:
I. What is conduction?
2. Use the molecular theory to explain conduction.
3. Explain three applications of conductors and insulators.


Meaning, molecular explanation. and application of convection
Convection is the process by which heat is transferred in a liquid or gas by the actual movement of the heated fluid from the hotter to the colder parts. Liquids and gases are poor conductors of heat but transfer heat by convection.

Molecular explanation of convection
When a liquid is heated the molecules expand, become less dense and rises. The denser molecules above take their places. Heat is therefore transferred by the moving molecules. This action continues and sets up a flow of water molecules called convection current.


https://youtu.be/HpCvWuvCUoA

Applications of convection
1. Land and sea breeze: This is convection current in nature. It happens in coastal area.
i. Sea breeze: In a hot day the sun warms the air near the land quickly than the sea because the earth has a lower specific heat capacity than the sea. This warm air rises. Cooler air from the sea moves to replace the risen air. This cool breeze from the sea is known as sea breeze.


ii. Land breeze: at night, the air above the sea is hotter. There is a conventional flow of hot air from the sea to the land and they are replaced by cool air from the land. The flow of cool air from the land to the sea is called the land breeze.

1. Ventilation: Air heated by respiration and fires rises towards the ventilators placed near the ceiling. This is replaced by fresh air from windows and other openings.

2. Cooling of motor car engine: Car engines require cooling to prevent overheating. The heat generated by the engine is conducted by the metal to the water in the jacket. The water is cooled by the air circulating round the radiator as the vehicle moved and by the cool air from the fan
3. The Domestic hot water system: Water is heated in the boiler by conduction through the metal. Hot water rises by convection to the cylinder, cold water flows in to take its place.


https://youtu.be/0CxkdJeqNfM

https://youtu.be/FTSBtx5jhaY

EVALUATION
Describe an experiment to show Convection current in water.

Radiation, Emission and radiation by different surfaces, The Thermos flask.

Radiation is the process by which heat is transferred from a hotter to a cooler place without heating of the intervening medium. Radiation is a mode of heat transfer that do not required a material medium for it transfer. Radiation can be detected by a radiometer and a thermopile. A thermopile detects and measures radiant energy.
A black surface is a better radiator and absorber of heat than a polished surface. This is why it is not advisable to wear a black cloth on a sunny day because one feels hot.
Polished surface, white surface and silvered surface are good reflectors of heat.


This device is used to prevent loss of heat energy from its content
The three modes of heat transfer are prevented in the thermos flask in the following ways:
1.The vacuum between the double walled glass prevents loss of heat by conduction or convection.
2. The silver colour of the inside of the double walls prevents heat loss by radiation
3. The cork support, or plastic prevents heat loss by conduction.
4. The cork stopper prevents heat loss by conduction, evaporation and convection.
https://youtu.be/iv5EbIrWgh4

GENERAL EVALUATION:
I. Mention the features and explain how heat losses are prevented in a Thermos flask.

ASSIGNMENT:
:
1. Some water is heated in a pot. The major mode(s) of heat transfer within the water is/are by
A. conduction. B. convection C. radiation D. conduction and radiation

2. Which of the following statements is not correct?
A. A sea breeze is due to convection in air
B. Cotton materials are better than woolen ones for use in hot weather.
C. Convectional currents play an important role in the cooling of the engine of a motor car.
D. The vacuum space in a flask helps to reduce heat loss by radiation.

3. The heating element in an electric kettle is usually located near the bottom of the kettle because
A. water is a good conductor of heat.
B. heat can be more quickly radiated to all parts of the water.
C. no heat can be lost to the surroundings.
D. the convectional current which are set up can carry heat to all parts of the water.
4. Which of the following does not need a medium for heat transfer?
A. conduction B. convection C. Radiation D. Evaporation
ESSAY

a. Mention two modes of heat transfer other than convection.
b. Explain land and sea breezes.
c. Describe an experiment each to show
i. Convection current in water
ii. Aluminium is a better conductor of heat than wood.
iii. Water is a poor conductor of heat.
d. Describe an experiment to show that blackened surfaces are better heat absorbers
than shiny surfaces.

PRE-READING ASSIGNMENT
Read Electric charges in your Text book.

ACTIVITY
List two types of charges and how they can be generated.

TOPIC: ELECTROSTATICS

CONTENT: 1. Types of charges
2. law of electrostatics
3. Gold leaf electroscope
4. Electrostatic induction
5. Ways of producing charges
6. Distribution of charges
7. Lightning conductor
8. Electrophorus


TYPES OF CHARGES, LAW OF ELECTROSTATICS, GOLD LEAF ELECTROSCOPE
Electrostatics is the study of charges at rest. It is electricity that does not move from one point to another in the substance in which it is produced.
https://youtu.be/VFbyDCG_j18

Types of charges:
Positive charge: A body becomes positively charged if it losses electron. This can be obtained in the Laboratory if glass rod is rubbed with silk and there is a net transfer of surface electrons from glass to the silk. The glass becomes positively charged and the silk becomes negatively charged.
Negative charge: A body is negatively charged if it gains electron. This is obtained by rubbing ebonite rod with fur and there is a transfer of electrons from the atoms of fur to the ebonite rod. The fur becomes positively charged. The positively charged protons deep in the nucleus are not free to be transferred.

Law of electrostatics: Like or similar charges repel each other; unlike or opposite charges attract each other.

Gold leaf Electroscope:
An electroscope is an instrument used for the detection and testing of small electric charges. It consists of a flat brass disc or cap, a brass rod with a gold leaf. The metal case is made draught-proof and connected to the earth to prevent accumulation of charges due to external influence.


An electroscope is a device which can detect electric charges. The casing is earthed so as to screen the leaf from outside interference of influence. The leaf is the sensitive or moving part of the instrument.




Uses of the Gold leaf Electroscope
1. To detect charges: If a charged body is placed on the cap of a charged electroscope an increase in divergence or collapse of the leaf shows the body is charged. If there is no change in the divergence, it means the body is not charged.
Use to test charges weather the charge is positive or negative. The gold leave electroscope to test the sign of the charge of an object. If an unknown charge is brought near to a charged electroscope and the leaf diverges more, the unknown charge is similar to the charge on the electroscope.

2. To determine the nature of charge on the body: If a charged body is placed on a charged electroscope, increase in divergence means the charge on the electroscope and the body are the same. If there is collapse of the leaf, it means they have opposite charge or the body is uncharged.

3. To determine the conducting properties of a body: If a good conductor is placed on the cap of an electroscope, the leaf collapses immediately. If it is a semi conductor, it collapses gradually and if an insulator, there is no alteration of the leaf
It is used to test weather a material is a conductor or an insulator. The material is made to touch the cap. Rapid collapse means that the charges escape easily and hence the material concerned is a good conductor. A slow collapse means that it is a poor conductor. No collapse means that it is an insulator.
https://youtu.be/6_s2P6BtZHc

Lighting and Lighting Conductor
The atmosphere is known to contain ions or charged particles, which have been produced by radiation from the sun and by what is known as cosmic radiation, which enters the atmosphere from outer space.
Lighting is a sudden discharge or neutralising of electric charges, and it occurs when charges build up in a cloud.
A lighting conductor is used to protect a building from lighting damage.
https://youtu.be/TOQJZCPngF0

EVALUATION
1. State two uses of an electroscope
2. Draw a well label diagram of an electroscope
3. What is the function of lighting conductors
4. Define lighting

Reading Assignment : New School Physics pg 58 -63

ASSIGNMENT
1. ……………… is a device use to detect charge (a) Electrophorus (b) Capacitor (c) Electroscope (d) Inductor
2. A lighting conductor is used to protect a building from lighting damage. (a) true (b) false (c) cannot say (d) none of the above
3. …………… is the sensitive part of an electroscope (a) The casing (b) The cap (c) The gold leaf (d) The brass rod
4. The casing of an electroscope is earthed so as to screen the leaf from outside interference (a) positively charge (b) negatively charge (c) neutral (d) none of the above
5. Capacitor is a device that …………. charges (a) produces (b) emits (c) store (d) none of the above
THEORY
1. Explain the two uses of an electroscope
2. Draw a well label diagram of an electroscope


Ways of producing charges.

1. Electrostatic induction
Electrostatic induction is the act of charging a neutral body by placing a charged body near it without any contact between the two.


STEP 1: A negatively charged body is brought near the uncharged body, free electrons from the metal sphere are repelled by the excess electrons on the rod. They shift towards the right. They can not escape from the sphere because the stand and the surrounding air are insulated.

STEP2: These excess charges called induced charges are released to the earth by touching the right part of the sphere with a wire and the other part of the wire to the earth.

STEP 3: The wire is disconnected.

STEP 4: The negatively charged rod is removed. A net positive charge is left on the rod.

https://youtu.be/8VN8MDn4CFA

2. Friction:
Charges can also be produced by friction. By rubbing as in ebonite and fur, glass rod and silk, charges are transferred from one by either of the two bodies involved. Equal and opposite charges are produced by friction.
https://youtu.be/gwsH8MHBWdc
Effects of charging by friction:
1. Passengers stepping out of cars and buses complain of a slight electric shock as soon as their feet touch the ground. This is because friction between the air and the body of the fast moving car makes the body of the vehicle to be charged.

2. A chain is often left hanging from the rear of a petrol tanker to discharge the charges acquired on the body during movement as this may cause a spark when inflammable vapour is present.

3. Contact:
This is done by bringing a charged body in contact with an uncharged body. Charges are transferred from the charged body to the uncharged body.

CHARGE DISTRIBUTION IN A CONDUCTOR
Charges are usually concentrated at places where the surface is sharply curved. The charge density is highest at the sharpest point of the conductor. For a hollow conductor, charges reside only on its outside surface, no charges reside inside the conductor.

https://youtu.be/UcwBmqd60C4
EVALUATION
1. What is electrostatic induction?
2. Explain the three methods of charging.




Lightning conductor and Electrophorus.
Lightning conductors are used to prevent tall buildings from being damaged when being struck by lightning. It helps to conduct the charges generated harmlessly to the earth. When electrical charges in thunderclouds build up, attraction between unlike charges within a cloud increases steadily until a heavy spark and sound is produced as the charges approach one another. This spark is observed as lightning and the sound is thunder. The heat generated can set a building or tree on fire.


ELECTROPHORUS
Electrophorus is used for storing and transferring electric charges. It consists of a metal disc fitted with an insulating handle and another flat disc made of insulating material such as ebonite.

https://youtu.be/_IWlDqZ-JMc
https://youtu.be/zrvIXhmDA7E

GENERAL EVALUATION
Explain the use of the following (i) Lightning conductor (ii) Electrophorus

ASSIGNMENT:
1. A building can be adequately protected from lightning by
A. using asbestos for the roof the house. B. Planting trees around the house.
C. Fixing a long copper strip from the ground along the outside wall to a sharp vertical spike.
D. Fixing a long wooden pole with sharp spikes to the outside wall.

2. Which of the following instruments can be used to compare the relative magnitudes of
charge on two given bodies?
A. The electrophorus B. Ebonite rod C. Proof plane D. Gold-leaf electroscope.
3. A short chain is usually attached to the rear side of a petrol tanker trailing behind it to ensure
that the
A. charges generated by friction in the tanker are conducted to the earth.
B. chain vibrates in resonance with the tanker’s engine.
C. heat generated by friction in the engine is conducted to the earth.
D. petrol tanker is balanced on the road.
4. The leaves of a negatively charged electroscope collapse completely as an object is brought close
to the cap of the electroscope. The object possesses
A. an equal quantity of negative charge B. an equal quantity of positive charge.
C. less quantity of negative charge.
D. less quantity of positive charge.
. 5. A dry plastic comb used in combing hair was found to attract pieces of paper and dust. The most probable explanation for this phenomena is that the comb has been given
A. magnetization by induction.
B. electric charges by induction
C. electric charges by conduction
D. electric charges by friction
ESSAY
1a List three ways of charging a conductor.
b. Describe how a conductor can be charged negatively by induction.
c. If a gold leaf electroscope is charged and left, the leaves gradually
collapses. Give TWO possible reasons for this.[2004].

2a. Give the reason why it is foolish to walk across an open space carrying an open
umbrella in thundery condition.
b. Describe how a lightning conductor protects a building from lightning.

PRE-READING ASSIGNMENT
Read current electricity from the text book

ACTIVITY
Construct an electroscope