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CUET · PHYSICS · PYQ PAPER 2025

A conducting circular loop is placed in a uniform magnetic field of \( B = 0.5 \text{ T} \), with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at the rate of \( \frac{dr}{dt} = 4 \text{ mm/s} \). When the radius of the loop is \( r = 4 \text{ cm} \), the induced emf in the loop is

  1. A \( 0.32\pi \text{ } \mu\text{V} \)
  2. B \( 1.6\pi \text{ } \mu\text{V} \)
  3. C \( 0.8\pi \text{ } \mu\text{V} \)
  4. D \( 160\pi \text{ } \mu\text{V} \)
Verified Solution

Answer & Solution

Correct Answer

(D) \( 160\pi \text{ } \mu\text{V} \)

Step-by-step Solution

Detailed explanation

\( \Phi_B = B A = B \pi r^2 \) \( \mathcal{E} = \left| -\frac{d\Phi_B}{dt} \right| = \left| -\frac{d}{dt}(B \pi r^2) \right| = \left| -B \pi (2r \frac{dr}{dt}) \right| = 2 B \pi r \frac{dr}{dt} \)…
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