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JEE Main 202622 JanuaryMorning Shift
Exam
JEE Main
Year
2026
Date
22 January
Shift
Morning Shift
Subject
Physics
Chapter
Electromagnetic Induction

JEE Main 2026 · 22 January · Morning Shift · Physics · Electromagnetic Induction

X P Q Y is a vertical smooth long loop having a total resistance R...

XPQYX P Q Y is a vertical smooth long loop having a total resistance RR where PXP X is parallel to QYQ Y and separation between them is ll. A constant magnetic field BB perpendicular to the plane of the loop exists in the entire space. A rod CDC D of length L(L>l)L(L>l) and mass mm is made to slide down from rest under the gravity as shown in figure. The terminal speed acquired by the rod is ____\_\_\_\_ m/s.(g=\mathrm{m} / \mathrm{s}.(\mathrm{g}= acceleration due to gravity)
X P Q Y is a vertical smooth long loop having a total resistance R where P X is parallel to Q Y and separation between

Options

  1. A(\frac{8 m g R}{B^2 l^2})
  2. B(\frac{2 m g R}{B^2 L^2})
  3. C(\frac{m \mathrm{~g} R}{B^2 l^2})
  4. D(\frac{2 m g R}{B^2 l^2})

Correct answer

C. (\frac{m \mathrm{~g} R}{B^2 l^2})

Step-by-step solution

As rod CD slides down with velocity vv, it cuts magnetic field lines.
Induced EMF: ε=BLv\varepsilon = BLv
Induced current in the circuit: I=BLvRI = \frac{BLv}{R}
Magnetic force on the rod (upward, by Lenz's law):
Fmag=BIL=B2L2vRF_{mag} = BIL = \frac{B^2L^2v}{R}
At terminal velocity, acceleration is zero.
Applying Newton's second law:
mg−Fmag=0mg - F_{mag} = 0
mg=B2L2vterminalRmg = \frac{B^2L^2v_{terminal}}{R}
vterminal=mgRB2L2v_{terminal} = \frac{mgR}{B^2L^2}
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