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Saturday, 31 October

JEE Main 2026 · PhysicsMultiple choiceSingle correctHardCalculation

JEE Main 5 April 2026, Shift 2, Physics Q36

Question 36 of 75 in this shift, Physics question 11 of 25, Section A.

A metal rod of length LL rotates about one end at origin with a uniform angular velocity ω\omega. The magnetic field radially falls off as B(r)=B0 e−λrB(r)=B_0\,e^{-\lambda r}; λ\lambda being a positive constant. The emf induced (neglecting the centripetal force on electrons in the rod) is :
  1. (1)B0ω[1λ2−e−λL(1λ2+Lλ)]B_0\omega\left[\frac{1}{\lambda^2}-e^{-\lambda L}\left(\frac{1}{\lambda^2}+\frac{L}{\lambda}\right)\right]Official answer
  2. (2)B0ω[1λ2+e−λL(1λ2+Lλ)]B_0\omega\left[\frac{1}{\lambda^2}+e^{-\lambda L}\left(\frac{1}{\lambda^2}+\frac{L}{\lambda}\right)\right]
  3. (3)B0ω[4λ2−e−2λL(1λ2+2Lλ)]B_0\omega\left[\frac{4}{\lambda^2}-e^{-2\lambda L}\left(\frac{1}{\lambda^2}+\frac{2L}{\lambda}\right)\right]
  4. (4)B0ω[3λ2−e−3λL(3λ2+Lλ)]B_0\omega\left[\frac{3}{\lambda^2}-e^{-3\lambda L}\left(\frac{3}{\lambda^2}+\frac{L}{\lambda}\right)\right]

Official answer

Option 1

NTA final key.