Question

(a) How does an electromagnet differ forma permanent magnet?
(b) Name two devices in which electromagnets are used and two devices where permanent magnets are used.

Answer 1

(a) Differences between an electromagnet and a permanent magnet:

Electromagnet		Permanent magnet
1.	It is a temporary magnet.	1.	As the name suggests, it is a permanent magnet.
2.	It can produce very strong magnetic force.	2.	It produces a comparatively weak magnetic field.
3.	Its polarity can be changed by changing the direction of current in the coil.	3.	Its polarity is fixed and cannot be changed.
4.	Its strength can be changed by changing the number of turns or by changing the current.	4.	Its strength cannot be changed.

(b) Uses of electromagnet:
1. In MRI scanners
2. In magnetic levitation train

Uses of permanent magnet:
1. In microphones
2. In electric clocks