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RRB Technician Grade I 19 Dec 2024 Shift 3 Paper

Question : 61 of 100

Marks: +1, -0

A wire loop is placed in a magnetic field that is increasing in magnitude but remains stationary. Using Fleming's Right-Hand Rule, what can be said about the induced current in the loop?

The direction of the current depends on the material of the loop
There is no induced current since the loop is stationary
The current is induced counterclockwise
The current is induced clockwise

Validate

Solution:

Concept:

A changing magnetic flux induces an emf, even if the loop is stationary.

Fleming’s Right-Hand Rule applies only when the conductor moves relative to the magnetic field.

Explanation:

The magnetic field magnitude is increasing, so the magnetic flux

\Phi_B = BA\cos\theta

through the loop changes with time.

By Faraday’s Law, the induced emf is

\mathcal{E} = -\frac{d\Phi_B}{dt}

, which is nonzero.

Hence an induced current is produced in the loop.

However, Fleming’s Right-Hand Rule requires motion of the conductor; here the loop is stationary, so this rule cannot be used to determine the direction of the current.

The direction is actually found using Lenz’s Law, which states that the induced current opposes the change in magnetic flux.

Since the direction of the external magnetic field is not specified, the current may be clockwise or counterclockwise.

Therefore, the statement “no induced current because the loop is stationary” is incorrect.

Answer:

None of the given options is correct.

An induced current will flow due to the changing magnetic flux, but its direction cannot be determined using Fleming’s Right-Hand Rule; it must be determined using Lenz’s Law.

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