Question

A coil of wire is wrapped around a cyliner-shaped piece of iron. Which of the following statements are true:

a) If current is made to flow in the wire, the iron cylinder becomes a magnet.

b) if the iron is a magnet, current is iduced to flow in the wire.

c) a & b are both true

d) a & b are both false

Answer 1

With only this given information we can say with a) is correct.

Let me make familiar with the phenomena :

When a coil is wrapped around a cylindrical shaped iron and current is passed through it then due to the current magnetic field is generated around the iron which starts to magnetise the iron piece, Hence making it Electromagnet.

This iron will remain to magnetise up until when the current is flowing through the wire once the current is turned off it loses its magnetism. Its a common example of "Solenoid".

b) - this is becoming magnetise through current only, if the current is off then it loses its magnetisation instantly so it does not act as a source of inducing the current.