A conductor AB is kept along north south direction of the earth above a magnetic needle as shown below. When the key K is closed then:

the needle will deflect towards east.

Reason — When key K is closed, electric current flows in the conductor from A to B. The conductor is placed along the north–south direction above the magnetic needle.

A current-carrying conductor produces a magnetic field around it. By applying the right-hand thumb rule, if the thumb points in the direction of current (A to B), the curled fingers give the direction of the magnetic field around the wire.

Since the magnetic needle is placed below the conductor, the magnetic field at the position of the needle is towards the East. Therefore, the magnetic needle deflects towards East.