Will the compass needle show deflection when the switch in the circuit shown by the figure is closed?

Why does a compass needle get deflected when brought near a bar magnet ?

Why does a compass needle get deflected when brought near a bar magnet?

A magnetic compass shows a deflection when placed near a current-carrying wire. How does the deflection of the compass get affected, if the current in the wire is increased ? Support your answer with a reason.

A child staying in a caostal region tests the drinking water and also the seawater with his tester.He finds that the compass needle deflects more in the case of sea water. Can you explain the reason ?