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# DC Circuits: Time Varing current and Voltages

Consider the circuit of Figure P4.18 in which the switch has been open for a long time prior to t=-0. Determine the values of vc(t) before t=0 and a long time after t=0. Also, determine the time constant after the switch closes and expressions for vc(t). Sketch vc(t) to scale versus time for -2 <= t <= 5.

Consider the circuit of Figure P4.19 in which the switch has been closed for a long time prior to t=0. Determine the values of vc(t) before t=0 and a long time after t=0. Also, determine the time constant after the switch opens and expressions for vc(t). Sketch vc(t) to scale versus time for -0.2 <= t <= 1.0.

Consider the circuit shown in Figure P4.24. The initial current in the inductor is iL(0-) = 0. Find expressions for iL(t) and v(t) for t >= 0 and sketch to scale versu stime.

Determine expressions for and sketch vR(t) to scale versus time for the circuit of Figure P4.27. The circuit is operating in steady state with the switch closed prior to t=0. Consider the time interval -0.2 <= t <= 1 ms.

#### Solution Summary

Four problems related to the expressions for time varying current and voltage in a circuit containing resistor, capacitor and inductor are solved.

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