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Question: Answered & Verified by Expert
A metal bar AB can slide on two parallel thick metallic rails separated by a distance l. A resistance R and an inductance L are connected to the rails as shown in the figure. A long straight wire, carrying a constant current I0 is placed in the plane of the rails as shown. The bar AB is held at rest at a distance x0 from the long wire. At  t = 0, it is made to slide on the rails away from the wire.



 It is observed that at time t=T, the metal bar AB is at a distance of 2x0 from the long wire and the resistance R carries a current i1. The net charge that has flown through resistance R from t=0 to t=T is
PhysicsElectromagnetic InductionJEE Main
Options:
  • A 1Rμ0l2πln2-Li1
  • B 1Rμ0I0lπln2-Li1
  • C 1Rμ0I0l2πln2-Li1
  • D 1Rμ0I02πln2-Li1
Solution:
2441 Upvotes Verified Answer
The correct answer is: 1Rμ0I0l2πln2-Li1
Let v be velocity of AB when AB is at a distance x from the wire,

e AB = B . . v = μ 0 I 0 2 π x I . v = d ϕ d t

For circuit Loop,

d ϕ d t - i R - L d i d t = 0

d ϕ d t - d q d t R - L d i d t = 0

d q = d ϕ - L d i R

Δ q = Δ ϕ - L Δ I R

= 1 R [ ϕ 1 - ϕ 2 - L i 1 ]

Δq=1R[μ0I02πln2-Li1]

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