7.70 Find Z in the circuit of Fig. P7.70, given that V; = 40 V and Va = 17.22e-j132.2° V. j4 2 3Ω Vs -j5 N :Va Figure P7.70: Circuit for Problem 7.70.

7.57 The switch in the circuit seen in Eig. P7.57 has been in position a for a long time. At t = 0, the switch moves instantaneously to position b. Find vo(t) and i, (t) for t 20+. Figure P7.57 15 mA 20 kn (1) 20 ΚΩ Σ 10 kn (125 nF 0² 25 mA

*7.58 Apply nodal analysis in the phasor domain to determine ic (t) in the circuit of Fig. P7.58. fic 1 1.6 592 20 mH m mF + 5Ω 20 mH 000 12 cos (400t - 30°) V Figure P7.58: Circuit for Problem 7.58. 3522 5Ω

For an RL circuit in Transient analysis, the current on the inductor follows: Iz (t) = K₁ + K₂ e 4 R To solve for IT (t), we need to know three parameters, i.e., K₁, K2, T. By observing the above expression, we find out that: IL (0)= K₁ + K2, IL (+00) = K₁. Now, we need to find values of IL (0), IL (+∞). In the following circuit, the switch is turned from A to B at t=0. VA 10V 44 A T B R 100 m VR(t)- Similar to RC transient analysis, let draw a time axis. Switch is at A v₁(t) Switch is at B t = 0 t = 0+ immt L 10H