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JEE Main 2005 (AIEEE) · Motional EMF

Motional EMF question from JEE Main 2005 (AIEEE)

Q57JEE Main 2005 · AIEEEMedium

Motional EMF

One conducting UU tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field BB is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed v,v, then the emf\text{emf} induced in the circuit in terms of B,lB, l and vv where ll is the width of each tube, will be

Figure

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Answer: (c)

  1. Both closed ends move towards each other, so the loop length shrinks at rate 2v2v.
  2. dAdt=l(2v)⇒ε=BdAdt\frac{dA}{dt} = l(2v) \Rightarrow \varepsilon = B\frac{dA}{dt}.
  3. ε=2Blv\varepsilon = 2Blv. So the answer is (c).
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