Imagine a current-carrying straight conductor with magnetic field of lines in anti-clockwise direction. Then the direction of current is determined by

CONCEPT:

Right-hand thumb rule:

• If we hold the current-carrying conductor in the right hand, the thumb points in the current direction, then the fingers encircled the wire in the direction of the magnetic field.

EXPLANATION:

• ​From the above, it is clear that the direction of current can be determined by the Right-hand thumb rule, and since the direction of the magnetic field is in the anti-clockwise direction, so if we place our right hand such that curl of our figure is in the direction of the magnetic field i.e., in an anti-clockwise direction, then our thumb will point out in the upward direction.

Additional Information

Maxwell's corkscrew rule:

• Imagine a right-handed corkscrew lying with its axis coinciding with the current-carrying wire.
• It is now rotated such that it advances in the direction of the current, then the direction in which the screw rotates gives the direction of the magnetic field.