Question

What happens to the needle of a compass kept nearby when electric current is switched on in a wire? Why does this happens?

Answer 1

1. When the current is passed through the circuit, the needle of the magnet deflects.

2. This because, a current carrying wire also generated a magnetic field around it.

2. Due to this, the magnet in the needle shows a deflection.

Answer 2

The needle of a magnetic compass starts deflecting when it is kept nearby a wire through which electric current is flowing. 
As electric current is flowing through the wire then a magnetic field gets surrounded around the wire. Now, as the needle of the compass is also a type of magnet. Therefore, this magnetic needle and the magnetic field suffer attractions and repulsions and hence the needle gets deflected.