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 Form 2 Physics Magnetic Effect of Electric Current Questions and Answers

The figure below shows an electromagnetic relay being used to switch an electric motor on and off. The electromagnet consists of a coil of wire wrapped around a core. The motor in figure is switched off.
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a).Suggest suitable material for the core.
(b) What happens to the core when switch S is closed?
(c) Why do the contacts A and B close when the switch S is closed.
d). When the switch S is opened, what will happen to?
(i) The core
(ii) Soft iron armature.
(e) Give one other application of an electromagnet.
(f) State two ways in which an electromagnet could be made more powerful.

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Answer Text:
a).Soft iron
b).The current flows through the solenoid; it is magnetized and attracts the soft iron armature;
c).The magnetized core attracts the soft iron armature. The pivot armature pushes the springy metal strip which joins contact B and A.
d i).It loses its magnetism.
ii).Soft iron goes back to its original position thus switching off the current in the circuit;
e).Electric bell, telephone receiver, moving coil loudspeaker and circuit breaker;
f).Using a soft iron core, increasing the current and increasing the number of turns;


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