Question

A current-carrying straight conductor produces a magnetic field. The direction of the field is given by:

• A. Ampere’s law
• B. Lenz’s law
• C. Right-hand thumb rule
• D. Faraday’s law

Hint:

To quickly find the direction of magnetic field lines around a straight wire, use your right hand: thumb = current direction, curled fingers = magnetic field direction. This is the Right-hand thumb rule.

Answer 1

The Correct Option is C

A magnetic field is produced around a straight conductor when current flows through it. The direction of this magnetic field is determined by the Right-hand thumb rule.
Right-hand thumb rule:
Grasp the current-carrying conductor with your right hand so that your thumb aligns with the current's direction. The direction in which your fingers curl around the conductor indicates the direction of the magnetic field lines.
This rule establishes that the magnetic field lines are concentric circles surrounding the conductor, with their direction dictated by the current's flow.
The following explains why alternative options are not applicable:
- Ampere’s law establishes a relationship between the magnetic field and the current that generates it but does not specify a directional rule.
- Lenz’s law addresses the direction of induced current resulting from a changing magnetic flux, not the direction of magnetic fields generated by conductors.
- Faraday’s law explains how a varying magnetic field induces an electromotive force (emf), but not the direction of magnetic fields originating from current.
Consequently, the right-hand thumb rule is the sole method that directly indicates the magnetic field direction for a straight current-carrying conductor.