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JEE Mains · Physics · STD 12 -6. Electromagnetic induction

A conducting circular loop is placed in a uniform magnetic field of \(0.4\,T\) with its plane perpendicular to the field. Somehow, the radius of the loop starts expanding at a constant rate of \(1\,mm / s\). The magnitude of induced emf in the loop at an instant when the radius of the loop is \(2\,cm\) will be \(...........\,\mu V\).

  1. A \(40\)
  2. B \(30\)
  3. C \(20\)
  4. D \(50\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(50\)

Step-by-step Solution

Detailed explanation

\(\frac{ dr }{ dt }=10^{-3}\,m / s\) \(\frac{ dA }{ dt }=2 \pi r \frac{ dr }{ dt }\) \(\varepsilon=\left|\frac{- d \phi}{ dt }\right|=\left|\frac{ BdA }{ dt }\right|\) \(=0.4 \times 2 \times \pi \times 2 \times 10^{-2} \times 10^{-3}\,V\) \(=16 \pi\, \mu V =50.24\,\mu V\)
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