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NEET 2010 (AIPMT, Prelims) · Magnetic Flux & Faraday's Law

Magnetic Flux & Faraday's Law question from NEET 2010 (AIPMT, Prelims)

Q81NEET 2010 · AIPMT · PRELIMSMedium

Magnetic Flux & Faraday's Law

A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of 1 mm s−1{}^{-1}. The induced emf when the radius is 2 cm, is

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Answer: (b)

  1. Field is perpendicular to the plane of the loop: ϕ=Bπr2⇒e=B⋅2πrdrdt\phi = B\pi r^2 \Rightarrow e = B \cdot 2\pi r\frac{dr}{dt}
  2. e=0.025×2π×0.02×10−3e = 0.025 \times 2\pi \times 0.02 \times 10^{-3}
  3. e=π×10−6e = \pi \times 10^{-6} V =π μ= \pi\ \muV
  4. So the answer is (b) π μ\pi\ \muV.
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