Question

A thick copper conductor is held parallel to a freely pivoted magnetic needle, as shown in the diagram alongside. Answer the question given below:

The direction of the magnetic field set up by the conductor carrying current is:

Options

• always in the direction of the current

• always against the direction of the current

• always at right angles to the direction of the current

• all of these

Answer 1

Always at right angles to the direction of the current

Explanation:

The magnetic field around a straight current-carrying conductor is made of concentric circular field lines. The plane of these circles is perpendicular to the conductor, so at any point the field direction is at right angles to the current direction. It is never along the current or directly opposite to it, so 'all of these' is wrong.