In the circuit shown below, R = 250 Q, L =.120 H, and epsilon = 45.0 V. Initially both switches are open and no current is flowing. Switch Si is closed at t = 0.00 s. What is the current flowing through the resistor at t = 0? What is the RL time constant? What is the current in the resistor after one RL time constant has passed? What is the voltage across the inductor at that time? What is the steady-state current in the resistor? S_1 is kept closed for a few minutes. If S_1 is opened and S_2 is closed at the same time, how long would you have to wait for the current to drop to one-fourth of its steady-state value? What is the voltage across the inductor at that time?
Resistance R = 250 ohm
Inductance L = 0.12 H
emf E = 45 volt
(a). Required current i = E/R
= 45 / 250
= 0.18 A
(b).RL time constant T = L/R
= 0.12 / 250
= 4.8 x10 -4 s
(c).Current after one RL time constant, i \' = 63 %of i
= 0.63 i
= 0.63 x0.18
= 0.1134 A
(d).voltage across resistor V = iR
= 0.1134 x 250 = 28.35 volt
So, voltage across inductor V \' = E - V
= 16.65 volt
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