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

When current flows through a straight conductor, it generates a magnetic field around it. The direction of this magnetic field is determined using the Right-hand thumb rule.
Right-hand thumb rule:
Imagine holding the current-carrying conductor in your right hand such that your thumb points in the direction of the current. Then, the curl of your fingers around the conductor gives the direction of the magnetic field lines.
This rule tells us that the magnetic field lines form concentric circles around the conductor, and their direction depends on the direction of current flow.
Let’s look at why the other options are incorrect:
- Ampere’s law relates the magnetic field in space to the current producing it but does not give a directional rule.
- Lenz’s law deals with the direction of induced current due to changing magnetic flux, not the direction of magnetic fields around conductors.
- Faraday’s law describes how a changing magnetic field induces an electromotive force (emf), but not the direction of magnetic fields from current.
Hence, only the right-hand thumb rule directly provides the magnetic field direction for a current-carrying straight conductor.