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JEE Main 2026 (23 Jan, Shift 1) · Motional EMF

Motional EMF question from JEE Main 2026 (23 Jan, Shift 1)

Q4JEE Main 2026 · 23 JAN · SHIFT 1Medium

Motional EMF

A 20 m long uniform copper wire held horizontally is allowed to fall under the gravity (g=10 m/s2)\left(g = 10\text{ m/s}^{2}\right) through a uniform horizontal magnetic field of 0.5 Gauss perpendicular to the length of the wire. The induced EMF across the wire when it travels a vertical distance of 200 m is ______ mV.

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Answer: (c)

  1. Speed after falling 200 m: v=2gh=2×10×200=2010v = \sqrt{2gh} = \sqrt{2\times10\times200} = 20\sqrt{10} m/s.
  2. B=0.5B = 0.5 G =5×10−5= 5\times10^{-5} T.
  3. ε=Blv=5×10−5×20×2010=0.0210\varepsilon = Blv = 5\times10^{-5} \times 20 \times 20\sqrt{10} = 0.02\sqrt{10} V
  4. =2010= 20\sqrt{10} mV. So the answer is (c).
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