physics test (unit 18-20)

7/29/2019 Physics Test (Unit 18-20)..

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

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

urn over[T

heory Section:

T

Time Allowed: 35Minutes

Maximum Marks: 25

NIQUE SCIENCE ACADEMYU

DateName

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 poweris 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 . Calculate

(i) the potential difference across a 3.0 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 resistor that carries a currentof 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 avoltage much lower than 23 000 V.

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

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

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

[Total 7]


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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 thecurrent 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 thewire is directly proportional to the current in it. He calculates the resistance of the wire andplots a graph of the resistance against the current.

0 current0

resistance

[1]


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Fig. 3.1

The graphs in Fig. 3.1 show the relation between the current3 I and the potential difference V for aresistor 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 sameresistance.

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

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

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

[Total: 7]4MCQ SECTION: [Total Marks]The current in a filament lamp is 0.25 A when working normally. The lamp is connected to a plugand 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 3 A.

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

D The live wire in the plug is not connected.


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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 fuseC 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

+6.0 V

0 V

2000

10 000

What is the reading on the voltmeter?

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

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

appliance fuse

A 100W lamp 1 A

B 1 kW vacuum cleaner 5 A

C 2 kW fan heater 3 A

D 3 kW electric fire 13 A

4 A B C D

3 A B C D

2 A B C D

1 A B C D

MCQ Answer Sheet

physics test (unit 18-20)

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