ASSIGNMENT BOOK Unit 8 Part 2 Part 2 Integrated Exercises (Unit Test) A. True or False (Total 20 marks; 2 marks each) Study each of the following statements

ASSIGNMENT BOOK Unit 8 Part 2

Part 2 Integrated Exercises (Unit Test)Part 2 Integrated Exercises (Unit Test)A. True or False (Total 20 marks; 2 marks each)

Study each of the following statements. Put a ‘T’ in the box against a correct statement and a ‘F’ against an incorrect statement.

1.All non-metals are good electric insulators.

T

F

2.An ammeter must be connected in series in a circuit.


3.Dry cells joined in series and in the same direction can give a larger voltage.

T

T

T

F6.The rating of a fuse shows the average

current which can flow through it without breaking the circuit.

5.The main sockets in our homes are connected in parallel.

4.The resistance of a long and thin copper wire is larger than that of a short and thick copper wire.

E


7. Too many appliances connected to one mains socket may lead to a short circuit.

F

F

F

T

8.A kilowatt-hour meter measures the electric power of the appliances.

E

9.All electrical appliances must have a heating element.

E

10.Electromagnets can be turned on and off.E


1. Which of the following substances is a good insulator of electricity?

A. carbon (graphite)

B. water

C. aluminium

D. rubber

B. Multiple Choice Questions (Total 40 marks; 2 marks each) Write the correct answer to each question in the box provided.

D


2. Which of the following is used to measure currents?

A

A. B.

C. D.


3. What is the ammeter reading shown on the right?

A. 0.16 A B. 1.3 A C. 1.6 A D. 3.0 A

C


A1

A2 A3

B

4. In the following diagram, if the lamps are all the same and the reading of ammeter A1 is 0.3 A, what are the readings of ammeters A2 and A3?

A. The ammeter readings of both A2 and A3 are 0.3 A.B. The ammeter readings of both A2 and A3 are 0.15

A.C. The ammeter reading of A2 is 0.3 A and that of A3

is 0 A.D. The ammeter reading of A3 is 0.3 A and that of A2

is 0.6 A.


5. The colour codes of the live, neutral and earth wires in a three-pin plug are?

A. brown, blue and yellow / green respectively.

B. red, brown and yellow / green respectively.

C. blue, brown and yellow / green respectively.

D. yellow / green, blue and brown respectively.

A


6. Look at the circuit below. The current through each of the lamps is 0.5 A. The rating of

the fuse connected in the main loop should be

A. 1.5 A.

B. 3 A.

C. 10 A.

D. 15 A.

B

mains supply


7. Study the following circuit diagrams.In which circuit does the voltmeter measure the voltage across bulb P?

D

A. B.

C. D.


8. In the diagram on the right, two identical bulbs A and B, are joined in series with a resistor to the battery. Which of the following statements is correct?

A. Bulb A is dimmer than bulb B.B. The bulbs are of equal brightness.C. Bulb A is brighter than bulb B.D. No current flows through the resistor. B


9. In which of the following cases does the bulb light up?

A. (1) onlyB. (2) and (3) onlyC. (2), (3) and (4) onlyD. (1), (2), (3) and (4) C

(1) (2) (3) (4)


10.The metal wires shown below are all made of the same material. Which of them has the greatest resistance?

D

A.

B.

C.

D.


11. Look at the picture on the right. What is the same of these small devices?

A. resistor B. rheostat C. circuit breaker D. fuse D


12. The earth wire of a circuit can?

A. protect the circuit from damage by a large currentB. conduct current safely to the ground if the live wire touches the casing of an electric appliance accidentally.C. break the circuit if the current is too large.D. save electricity.

B


13. Look at the picture below.

A fuse in a three-pin plug should be connected to:A. Pin X.B. Pin Y.C. Pin Z.D. Pin X or Pin Z. A

Pin Y

Pin X

Pin Z


14.Which of the following(s) is / are the advantages of using ring circuit in our homes?

(1) It can save electricity.(2) Thinner and cheaper wires can be us

ed.(3) It can prevent overloading.

A. (1) onlyB. (2) onlyC. (1) and (2) onlyD. (2) and (3) only

B


1.5 V dry cell

metal wire

15.Name the fault as shown in the picture on the right.

A. overloadingB. earthingC. short circuitD. overheating

C


16. Overloading occurs if

A. we do not connect the earth wire to an electrical appliance.

B. we do not use a fuse in a three-pin plug. C. we connect too many electrical

appliances to one mains socket. D. a circuit is shorted.

C


17. Which of these circuits is a ‘short circuit’?

A. B.

C. D.

A


A

18. An electric iron has a power rating of ‘220 V 1000 W’. That means

A. At a voltage of 220 V, 10 J of electrical energy are transferred to it in one second.

B. At a voltage of 220 V, 1000 J of electrical energy are transferred to it in one minute.

C. At a voltage of 220 V, 1000 W of electrical energy are transferred to it in one second.

D. At a voltage of 220 V, 1000 W of electrical energy are transferred to it in one hour.

E


A

19. A table lamp has a power rating of ‘220 V, 100 W’. What is its normal operating current?

A. 0.45 A B. 2.2 A C. 4.5 A D. 22,000 A

E


20. Which of the following appliances makes use of both the magnetic and heating effects of currents?

B

A. B.

C. D.

electric kettle television

hair dryertoaster


1.Study the electric below.C. Question (Total 40 marks)

X


(a) Draw a circuit diagram for the above electric circuit. (2 marks)


(b) If the ammeter reading is as shown below, what is the current flowing in the main circuit? (1 mark)

Current flowing in the main circuit = _____0.8 A


(c) What will happen to the current in the main circuit if bulb X is removed? (2 marks) ___________________________________The main circuit current will decrease.


open

Switch A Switch B Lamp

open

open

open

closed

closed

closed closed

2.The lamp shown on the right can be controlled by switches at the front door and the rear door.

Complete the table below. (3 marks)

off

on

on

on


a switch a 10-Ω rheostat some connecting wirestwo dry cells a small light bulb

3.You are provided with the following materials:

(a) Use the materials provided to design a circuit in which the brightness of the bulb can be

adjusted. Draw a circuit diagram in the box below to show your design. (2 marks)



(b) What is the meaning of a 10-Ω rheostat? (2 marks)__________________________________________________________________________The resistance of the rheostat can be changed from 0 Ω to 10 Ω.


4. The two bulbs in the circuit below are identical.

(a) If the ammeter reading is 1.2 A, what is the current flowing through bulb A?

(1 mark)

_________________________________

A

B

0.6 A


(b) Another identical bulb C is added to the circuit as shown below.


(ii) Add circuit symbol to the above circuit diagram to show how you would measure the voltage across bulb C. (1 mark)

(i) What would be the new ammeter reading? (1 mark)______________________________________1.8 A


A

B

C


(iii) What would happen to the ammeter reading if more identical bulbs are added in parallel to the circuit? (2 marks)______________________________________

The ammeter reading would increase.


5. Study the diagram below and then answer the questions that follow.

power supply

fuse


(b) What is the function of the fuse in the circuit? (2 mark)__________________________________________________________________________

(c) If the operating current of the bulb is 0.6 A and we have fuses with the following ratings: 0.5 A, 1 A, 2 A and 5 A, which fuse would you choose? (1 mark)_____________________________________

The heating effect of the current.

If there is too large a current, it will melt and break the circuit.

1 A fuse

(a) Name the effect which makes the bulb light up. (1 mark)_____________________________________

E


(d) Can we use a piece of copper wire as the fuse wire? Explain briefly. (2 marks)_____________________________________No, its melting point is too high.

(e) If we ‘short’ the bulb, what would happen to the current in the circuit? What would happen to the fuse wire? (2 marks)__________________________________________________________________________The current would become very large. The fuse wire would become very hot and melt.


6.Johnny’s family does not know much about electricity safety. Each of the family members has made a mistake, what are they? (8 marks)

MotherFather

Johnny Sister


________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Johnny should not repair electrical appliance by himself.Johnny’s mother should not use the iron with a worn-out wire.Johnny’s father should not handle electrical sockets with a wet hand.Johnny’s sister should not use the electrical appliances with a two-pin plug.


power supply

7. The following diagram shows a simplified structure of a circuit breaker. Study it carefully and fill in the blanks in the following passage. (7 marks)

E


Normally, the switch S is closed. A(a) _______________ passes through the circuit and the light bulb will be (b) _______________ . However, if the current in the circuit is too large, the (c) _______________ effect of the current will be large enough to (d) _______________ switch S.

The circuit will then be (e) _______________ and no (f) _______________ will flow through. This device acts in a similar way as a(g) _______________ which prevents the appliance from damage by extremely large currents.

currenton

magneticattract

opencurrent

fuse

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ASSIGNMENT BOOK Unit 8 Part 2 Part 2 Integrated Exercises (Unit Test) A. True or False (Total 20 marks; 2 marks each) Study each of the following statements