Question

An electric current passes through a straight wire. Magnetic compasses are placed at the points A and B.

• A. Their needles will not deflect
• B. Only one of the needles will deflect
• C. Both the needles will deflect in the same direction.
• D. The needles will deflect in the opposite directions.

Answer 1

The correct option is D The needles will deflect in the opposite directions.

Current carrying wire produces magnetic field, but direction of magnetic field on the given points A and B are different.

This is found by right hand thumb rule. So magnetic compasses on A and B experience magnetic force of same magnitude but in opposite directions. Hence, the needles will deflect in opposite directions.