Question

Chapter 7, Problem 7.048 (Circuit Solution) Use the step-by-step method to find /0(80 ms) in the network in the figure below io(t) mA

Answer 1

In the given circuit, the switch is opened at t = 0 circuit diagram at t = 0^- voltage across capacitor at t = 0^- (in steady state) = voltage across 6k Ohm resistor (as capacitor is directly parallel to it and at t = 0^- it will act as open circuit) I = 12/Req = 12/4k Ohm = 3 mA Therefore I_1 = 3 - A/6 + 12 times 6 = 1mA Therefore v_c = 6k Ohm times 1mA = 6v circuit diagram at t = 0^+ Rightarrow Now according to formula i (f) = I (infinity) + [i (0^+) - I (infinity)] e^- t/c where I (infinity) = current in the circuit after t = infinity = 0 Amp (as capacitor will act as open circuit when fully charged at t = infinity) i (0^+) = current in the circuit just after switching at t = 0 \r\n Now, since capacitor resistors instantaneous change in voltage Therefore v_c (0^-) = v_c (0) = v_c (0^+)
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