Question

A long straight wire is held vertically and carries a steady current in upward direction. The shape of magnetic field lines produced by the current-carrying wire are :

• A. horizontal straight lines directed radially out from the wire.
• B. straight lines parallel to the current-carrying wire.
• C. concentric horizontal circles around the wire.
• D. coaxial helixes around the wire.

Answer 1

The Correct Option is C

When a steady current flows through a long straight wire, the magnetic field lines form concentric circles around the wire, as per Ampere’s Law. The direction of the magnetic field lines follows the right-hand rule: if you curl the fingers of your right hand around the wire in the direction of the current, your thumb points in the direction of the magnetic field.

Therefore, for a vertical current-carrying wire, the magnetic field lines will be horizontal and form concentric circles around the wire.