:........................................................ Code: 5054 Class: CIIA

Test (Unit 18-20) :................................................................................................................

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heory Section:

T

Time Allowed: 35Minutes

Maximum Marks: 25

NIQUE SCIENCE ACADEMY U

Date

Name

Paper: Physics

1

Dedicated to My Son Mohammad Irtaza Zain. Code 5054

This document consists of 4 printed pages.

[Total 21 Marks]

1 The current in the transmission line used to supply electrical power to a village is 65 A. The power is transmitted at a voltage of 23 000 V.

(a) Calculate the power supplied to the village.

power = ...........................................................[2]

(b) The transmission line has a resistance of 3.0 Ω. Calculate

(i) the potential difference across a 3.0 Ω resistor that carries a current of 65 A,

potential difference = ...........................................................[2]

(ii) the thermal energy (heat) produced in 1.0 s in a 3.0 Ω resistor that carries a current of 65 A.

heat = ...........................................................[1]

(c) (i) State one advantage of transmitting electrical power at a high voltage.

...........................................................................................................................................

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

(ii) Suggest one reason why the mains power supply to the houses in the village is at a voltage much lower than 23 000 V.

...........................................................................................................................................

...........................................................................................................................................

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

[Total 7]Irtaz

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[Total 7]

Fig. 2.1

On Fig. 2.1, sketch the shape of this graph.

2 An electrical engineer measures the potential difference across a length of metal wire and the current in the wire. He does this for different values of the current.

(a) (i) Draw a labelled circuit diagram of a circuit that enables the engineer to do this.

[3]

(ii) Describe how the circuit is used.

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

.......................................................................................................................................[2]

(iii) State the equation that defines resistance.

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

(b) The engineer performs the experiment and notices that the potential difference across the wire is directly proportional to the current in it. He calculates the resistance of the wire and plots a graph of the resistance against the current.

0 current0

resistance

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Fig. 3.1

The graphs in Fig. 3.1 show the relation between the current 3 I and the potential difference V for a resistor and a lamp.

00 1 2 3 4 5 6

V /V

7 8 9

1

2

3

4I /A

5

6

lamp

resistor

(a) (i) Describe how, if at all, the resistance varies as the current increases in

1. the resistor, ...................................................................................................................

2. the lamp. ...................................................................................................................[2]

(ii) State the value of the potential difference when the resistor and the lamp have the same resistance.

potential difference = ...........................................................[1]

(b) The two components are connected in parallel to a supply of e.m.f. 4.0 V. Calculate the total resistance of the circuit.

total resistance = ...........................................................[4]

[Total: 7]4 MCQ SECTION: [Total Marks] The current in a filament lamp is 0.25 A when working normally. The lamp is connected to a plug

and the mains a.c. supply.

When the lamp is switched on, it does not light.

What is a possible cause for this?

A The earth wire in the plug is not connected.

B The fuse in the plug is 3A.

C The lamp only works on a d.c. power supply.

D The live wire in the plug is not connected. Irtaz

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Dedicated to My Son Mohammad Irtaza Zain. Code 5054

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The diagram shows an unsafe use of an extension cable.

What is the electrical hazard?

A the danger of burning out the appliances

B the danger of melting the fuse

C the danger of overheating the cable

D the danger of the appliances not being earthed

3 The diagram shows a potential divider system of two resistors connected to a 6.0V power supply.

V

+6.0V

0 V

2000Ω

10 000Ω

What is the reading on the voltmeter?

A 1.0V B 1.2 V C 3.0 V D 5.0 V

4 Which appliance used on a 240V supply is most likely to burn out its fuse?

appliance fuse

A 100W lamp 1A

B 1kW vacuum cleaner 5A

C 2kW fan heater 3A

D 3kW electric fire 13A

4 A B C D

3 A B C D

2 A B C D

1 A B C D

MCQ Answer SheetIrtaz

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