Question

When current passes through the circuit a compass needle rests in which direction with respect to the earth:
(A) South-north
(B) North-south
(C) East-west
(D) West-east

Answer 1

Hint : We know that earth is a massive magnet and has a huge magnetic field whenever we place the compass in earth’s magnetic field it always points towards the north direction. But when the current is passed through the circuit where the compass is placed nearby or in the electric field. It shows different directions.

Complete Step By Step Answer:
We are given the compass and we know that the compass will always direct the direction of the earth’s magnetic field i.e. north-south direction but it is also given that the compass is kept in the influence of electric field since the current is passed through the circuit. This circuit creates the electric field and the compass shows the deflection when it comes in the influence of the electric field generated by the circuit . This deflection in the needle shows exactly the opposite direction to that it showed when it was in the influence of earth’s magnetic field.
So, we have concluded that the compass will show the opposite direction than that of the previous one when it was not in the electric field. After passing current in the circuit the needle will show south-north direction.
Therefore, the correct option is A.

Note :
We must know that the direction shown by the needle in the compass is always pointing towards the north. The electric field changes the direction of the magnetic needle such that it becomes almost opposite to that of the magnetic field direction. To know further details you must study Oersted's law.