Question

The direction of the magnetic lines of force due to a current-carrying straight conductor when the electric current flows upwards is

• A. anticlockwise
• B. sometimes clockwise sometimes anticlockwise
• C. clockwise
• D. none of these

Answer 1

The correct option is A

anticlockwise

1. Maxwell's right-hand thumb rule gives the direction of lines of force of the magnetic field produced by a straight conductor (wire) carrying current.
2. If we hold the current-carrying conductor in your right hand so that your thumb points in the direction of the current, then the direction in which your fingers encircle the conductor will give the direction of magnetic lines of force around the wire.
3. If when the electric current flows in an upwards direction in a straight conductor then keeping the right-hand thumb in the upward direction the fingers encircle will give the direction of the magnetic field.
4. So, the fingers will encircle in an anticlockwise direction.

Hence, option A is correct.