Question

The magnetic field at a distance r from a long wire carrying current I is 0.4 tesla. The magnetic field at a distance 2 r is ______.

Options

• 0.1 tesla

• 0.2 tesla

• 0.6 tesla

• 0.8 tesla

Answer 1

The magnetic field at a distance r from a long wire carrying current I is 0.4 tesla. The magnetic field at a distance 2 r is 0.2 tesla.

Explanation:

A straight conductor's magnetic field varies inversely with the distance between the observation location and the conductor. As a result, when the distance between the magnets is extended from r to 2 r, the magnetic field becomes `0.4/2` = 0.2 tesla.