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JEE Main 2014 · Inductors & DC Transients (Mixed)

Inductors & DC Transients (Mixed) question from JEE Main 2014

Q26JEE Main 2014Medium

Inductors & DC Transients (Mixed)

In the circuit shown here, the point ′C′'C' is kept connected to point ′A′'A' till the current flowing through the circuit becomes constant. Afterward, suddenly, point ′C′'C' is disconnected from point ′A′'A' and connected to point ′B′'B' at time t=0.t = 0. Ratio of the voltage across resistance and the inductor at t=L/Rt = L/R will be equal to:

Figure

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Answer: (c)

  1. After C is joined to B, the battery is out and R and L form a closed loop on their own.
  2. Kirchhoff's loop rule: VR+VL=0V_R + V_L = 0 at every instant, so VL=−VRV_L = -V_R.
  3. So VRVL=−1\frac{V_R}{V_L} = -1 at any time, including t=L/Rt = L/R.
  4. So the answer is (c) −1-1.
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