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JEE Main 2021 (20 Jul, Shift 1) · Motional EMF

Motional EMF question from JEE Main 2021 (20 Jul, Shift 1)

Q43JEE Main 2021 · 20 JUL · SHIFT 1Difficult

Motional EMF

The arm PQ of a rectangular conductor is moving from x = 0 to x = 2b outwards and then inwards from x = 2b to x = 0 as shown in the figure. A uniform magnetic field perpendicular to the plane is acting from x = 0 to x = b. Identify the graph showing the variation of different quantities with distance.

Figure

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Answer: (b)

  1. Flux: rises linearly from 00 to bb (area in field grows), stays constant from bb to 2b2b and back to bb, then falls to zero. This is graph A.
  2. EMF =−dϕdt= -\dfrac{d\phi}{dt}: constant while going out (00 to bb), zero outside the field, constant with opposite sign while coming back. This is graph B.
  3. Power =e2R= \dfrac{e^2}{R}: same positive value in both field stretches, zero elsewhere. This is graph C.
  4. So the answer is (b) A-Flux, B-EMF, C-Power dissipated.
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