question_answer

The diagram shows a plotting compass placed above a copper wire when there is no current flowing in the wire. What happens to the compass needle when a large direct current flows from point A to point B?

A)  The compass needle points towards the right.

B)  The compass needle points towards the left.

C)  The compass needle points towards upward.

D)  The compass needle points toward downward.

Correct Answer: D

Solution :

A current-carrying wire will produce circular magnetic field around the wire. The direction of the magnetic field follows the right hand grip rule. When the current flows from A to B, the magnetic field around the wire is shown in the figure. Since the compass is placed in front of the wire, it will follow the direction of the magnetic field and turn to the right.