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 :
- horizontal straight lines directed radially out from the wire.
- straight lines parallel to the current-carrying wire.
- concentric horizontal circles around the wire.
- coaxial helixes around the wire.
The Correct Option is C
Solution and Explanation
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.
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