COMEDK · Physics · 22. Electromagnetic Induction

A metallic circular loop is placed with its plane perpendicular to a uniform magnetic field of 0.3 T. If the radius of the loop decreases at a constant rate of \(2\ mm\ s^{-1}\), what will be the induced emf in the loop, when the radius of the loop becomes 5 cm.

A \(1.89 \times 10^{-4}\ V\)
B \(0.75 \times 10^{-6}\ V\)
C \(1.84 \times 10^{-6}\ V\)
D \(1.5 \times 10^{-6}\ V\)

Verified Solution

Answer & Solution

Correct Answer

(A) \(1.89 \times 10^{-4}\ V\)

Step-by-step Solution

Detailed explanation

Magnetic flux through the loop is given by \(\Phi = BA = B\pi r^2\) According to Faraday's law of induction, the magnitude of the induced emf is: \(|e| = \left| \dfrac{d\Phi}{dt} \right| = B \cdot 2\pi r \left| \dfrac{dr}{dt} \right|\) Given: \(B = 0.3\ T\)…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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