$A$ compass needle is placed near a current-carrying wire. State your observation for the following cases and give the reason for the same in each case:
$(a)$ Magnitude of electric current in the wire is increased.
$(b)$ The compass needle is displaced away from the wire.

(N/A) The deflection of the compass needle increases. Reason: The strength of the magnetic field produced by a current-carrying wire is directly proportional to the magnitude of the electric current flowing through it.
$(b)$ The deflection of the compass needle decreases. Reason: The strength of the magnetic field produced by a current-carrying wire is inversely proportional to the distance from the wire.