Question

A circular loop of radius $r$ is moved away from a long current carrying wire, then induced current in the circular loop will be -

Assume the loop and wire are in the plane of paper of your notebook and the observer is observing from above the plane.

• A. Clockwise
• B. Anti-clockwise
• C. No current will be induced
• D. Initially clockwise, then anti-clockwise

Answer 1

The correct option is A Clockwise

Magnetic field due to infiinte wire is given by,

$B=\frac{{\mu }_{0}i}{2\pi d}$

Where, $d$ is the perpendicular distance from the wire.

The direction of magnetic field is inward and perpendicular to the plane of loop.

As the loop is moving away from the wire, the magnetic field due to the wire is decreasing. Therefore, the inward flux linked with the coil is also decreasing as $\varphi =BA\cos \theta$

According to the Lenz's law the current will flow in such a way that it opposes the decreasing magnetic flux through the coil, as shown in the figure.

Therefore, the induced current will flow in clockwise direction.

Hence, option ($A$) is the correct answer.