What is the rms value of the voltage 37 Determine the true p

What is the rms value of the voltage? 37. Determine the true power and the reactive power in Problem 36. SECTION 9-7 Capacitor Applications 38. If another capacitor is connected in parallel with the existing capacitor in the power supply iter 39. of Figure 9-52, how is the ripple voltage affected? Ideally, what should the reactance of a bypass capacitor be in order to eliminate a 10x voltage at a given point in an amplifier circuit? ADVANCED PROBLEMS 40. Two series capacitors (one l F, the other of unknown value) are charged from a 12 V sure. The 1 F capacitor is charged to 8 V, and the other to 4 V. What is the value of the unknown capacitor. 41. How long does it take C to discharge to 3 V in Figure 9-68? 42. How long does it take C to charge to 8 V in Figure 9-67? 43. Determine the time constant for the circuit in Figure 9-71. 1.0 k 1.0 k 2 R2 2.2 k 0.0022 F 50 v 1.5 k

Solution

time constant (tau)= R*C =1*10^3*1.5*10^-6 = 1.5msec

V0= Vi*exp(-t/tau) => 3 =25 * exp(-t/1.5*10^-3)

                              apply ln on both sides => ln 3 = ln 25 - t/(1.5*10^-3)

                                  t= 2.1202 * 1.5*10^-3 = 3.1803mseconds