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CHAPTER 8

GENERATION OF ELECTRICITY

Name: .. Class: ............

1. Diagram 1 shows a simple transformer which is made of two coils of wire wrapped around

an iron core.

(a) What type of transformer is this?

..

[1 mark]

(b) What is the use of this transformer?

..........

[1 mark]

(c) Label coil P and coil Q on Diagram 1.[2 marks]

(d) Compare the brightness of bulb R and bulb S.

[1 mark]

(e) What will happen to the brightness of bulb R and bulb S if coil P and coil R are

reversed?

..........[1 mark]

191

P:

Q:

RS

Diagram 1

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2. Diagram 2 shows the structure of a 3-pin plug

(a) On Diagram 2, label structure P, Q and R using the following words.

Live wire Earth wire Neutral wire

[3 marks]

(b) Draw line to show the correct match between the wires and their functions

[3 marks]

192

Diagram 2

P:..

Q:..

R:..

S

Wire Function

PQ

R

Carry electriccurrent back to themainsCarry leakedcurrent to the Earth

Carry electric current tothe electrical appliance

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(c) Draw line to show the correct match between the wires and their colours.

[3 marks]

(d) (i) Name the component labelled S.

[1 mark]

(ii) State the function of the component labelled S

..[1 mark]

3. Diagram 3 shows two commercial methods of generating electricity commonly used inMalaysia.

(a) Name the type of electric generator shown in Diagram 3.

P :.......

Q: ...[2 marks]

193

Wire Colour

PQ

R

Blue

Brown

Yellow withgreen stripes

Diagram 3

P Q

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(b) State the energy change that takes place in Q.

..[1 mark]

(c) State one disadvantage of using P to generate electricity.

[1 mark]

(d) State one advantage of using Q to generate electricity.

[1 mark]

(e) Apart from P and Q, name another type of electrical generator used in Malaysia.

[1 mark]

4. Diagram 4.1 shows the electrical wiring system in the house.

(a) On Diagram 4.1, label P, Q and R with the following words.

Fuse box Main fuse Electric meter

[3 marks]

(b) What is the function of

(i) P?

(ii) Q? ..[2 marks]

194

Diagra

m 4.1

P:

Q:..

R:

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(c) Why are the lights in the lighting circuit connected in parallel?

[1 mark]

(d) Diagram 4.2 shows the readings of an electric meter for a household.

(i) Calculate the number of electrical energy units used by the household.

[2 marks]

(ii) Table 4.3 shows the rate of electrical energy charged by the electrical powersupplier.

Charge Unit Rate

First 200 RM 0.32

Consecutive 500 RM 0.38

Table 4.3

Calculate the cost of electrical energy used by the household in (d)(i).

[2 marks]

195

0 4 6 52 5

kWh

PreviousReading

0 4 9 32 8

kWh

CurrentReading

DIAGRAM 4.2

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5. Diagram 5 shows the electrical energy transmission and distribution system.

(a) Label P, Q and R on Diagram 5 using the following words.

Switch zone Power station Main substation

[3 marks]

(b) What is the function of Q?

[1 mark]

(c) What is the difference between M and N?

[1 mark]

(d) State one advantage of the National Grid Network.

[1 mark]

196

P:..

Q:..

Diagram 5

R:

M

N

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7. Figure 7.1 shows the distribution system of electrical supply. P,Q,R and S are transformers

11 kV 132 kV 66 kV 11 kV 11 kV

FIGURE 7.1

a) Based on Figure 7.1, state two step-down transformers

and .[1 mark]

b) Draw the number of turns for primary coil and the number of turns for secondary coil

respectively to show a step-up transformer on Figure 7.2

.

Input voltage Output voltage

FIGURE 7.2

c) In the electricity transmission and distribution system a step-up transformer is placed inthe field zone. Give your reason.

. ..

[1 mark]

198

Po

w

er

stat

io

n

P Q

P

R

P

SDivision

al

Sub

station

He

av

yind

ust

ry

Lig

ht

indust

ry

Cit

y

Ho

use

s

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d) A group of student carried out an experiment in which the number of turns in primary coilwas kept constant while the number of turns in secondary coil was increased . Therespective coil and output voltage are shown in table 7.3

Number of turns in secondary coil Output voltage

8 40

10 50

12 60

14 80

Table 7.3

i) Estimate the output voltage if the number of turns in secondary coil are 13

..[1 mark]

ii) State the relationship between the number of turns in secondary coil andthe output voltage

...

...[1 mark]

e) Parts of electrical wiring system at home consists of circuit breaker, main switch,electrical meter and main fuse.

Arrange the component of wiring system at home in correct sequence in Figure7.4

Figure 7.4[2 marks]

f) Ali watched television from 8 p.m to 10.00 p.m. After that he used computer forone hour. If television and computer have 100W power respectively, calculate thetotal cost for both appliances. (Cost for one unit is RM0.20)

[2 marks]

199

m Ci

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200

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201

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202