a	Name: _______________________________________________ 	

  	
  	
The motor effect	

 	
Date:	

  	
  	
Time: 35 minutes 	
  	
Total marks available: 35 	
  	
Total marks achieved: ______ 	

  	

  	

  	

  	

  	

  	

  	
Answer questions in the spaces provided  	

	

Questions

Q1.

The diagram shows a piece of card and two wide bar magnets.

(a) (i) Add to the diagram to show the shape and direction of the magnetic field
pattern between the magnets.
(3)
(ii) Describe how to investigate the shape and direction of the magnetic field
between the magnets.
(3)
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(b) A metal rod, X Y, is placed in a magnetic field as shown.

Wires from a cell are connected to the ends of the rod so that there is a current
from X to Y.

(2)
Describe the effect on the rod.
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(Total for question = 8 marks)

Q2.
 
Diagram 1 shows some of the apparatus used to investigate the force on a current-carrying wire, XY, in a magnetic field.

(a)  Diagram 2 shows the poles of the magnet viewed from above.
Draw the uniform magnetic field between the poles.
(2)

(b)  The current-carrying wire XY is at right angles to the magnetic field.
The current in the wire is 10 A.
(i)  Suggest why the wire used in this investigation must be thick.
(1)
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(ii)  Explain why the wire XY experiences a force when there is a current in the circuit.
(3)
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(iii)  State two ways in which this force can be reduced.
(2)
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(Total for question = 8 marks)

Q3.

The photograph shows a simple d.c. electric motor.

(a) When the switch is closed the coil spins.
Explain why this happens.
(3)
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(b) (i) Describe two ways to increase the speed of rotation of the coil in this motor.
(2)
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(ii) Suggest how to make the coil spin in the opposite direction.
(1)
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(c) In a different motor, the magnets are curved and there is a piece of iron inside the
coil. The iron increases the strength of the magnetic field through the coil.

Suggest how the curved magnets and the piece of iron improve the performance
of the electric motor.
(2)
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(Total for question = 8 marks)

Q4.

A student is listening to a radio.

(a) The radio is powered by batteries that provide a direct current (d.c.).

What is direct current?
(1)
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(b) Radio waves are part of the electromagnetic spectrum.

(i) Suggest a property of radio waves that makes them suitable for use in communication.
(1)
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(ii) Complete the table to show uses and possible harmful effects of some other
parts of the electromagnetic spectrum.
(4)

(c) In the radio, sound is produced by a loudspeaker.

The diagram shows the construction of a loudspeaker.

Describe how a loudspeaker uses an electrical supply to produce sound waves.
(5)
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(Total for question = 11 marks)