Physics - EMI/AC Question with Solution | TestHub

PhysicsEMI/ACL-R circuitHard2 minPYQ_2018
PhysicsHardmultiple choice

In the figure below, the switches S1 and S2 are closed simultaneously at t = 0 and a current starts to flow in the circuit. Both the batteries have the same magnitude of the electromotive force (emf) and the polarities are as indicated in the figure. Ignore mutual inductance between the inductors. The current I in the middle wire reaches its maximum magnitude Imax time t =τ. Which of the following statements is (are) true?

Options:(select one or more)

Answer:
B, D
Solution:

The current in the middle, I, as shown in the figure above has a maximum value,
imax=i2-i1max

Using the equation of current decay in an L-R circuit, for the given values in the figure above,
i=i2-i1=VR1-e-R2Lt-VR1-e-RLt
VRe-RLt-e-R2Lt
For imax, didt=0
VR-RLe-RLt--R2Le-R2Lt=0
e-RLt=12e-R2Lt
e-R2Lt=12
R2Lt=ln2
t=2LRln2 time when I is maximum
imax=VRe-RL2LRln2-e-R2L2LRln2
imax=VR14-12=14VR

Stream:JEE_ADVSubject:PhysicsTopic:EMI/ACSubtopic:L-R circuit
2mℹ️ Source: PYQ_2018

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