Answer: B. 92. What is time constant for the circuit in Fig.10?
92. What is time constant for the circuit in Fig.10? A. 3L/5R B. L/3R C. 2L/3R D. 3R/2L E. 2L/5R Fig. 10
Solution: TC=GNL
Answer: A.
93. What is time constant for the circuit whose solution is iL(t)=30e-200t-20 mA t≥0. A. 10 ms B. 20 ms C.1ms D. 5 ms E. 30 ms
Solution: iL(t)=[iL(0) – iL(∞)]e-t/Tc+ iL(∞); -t/TC= -200t 1/TC=200 TC=1/200=0.005=5 ms Answer: D.
94. What is differential equation whose solution is vC(t)= - 20e-1000t+20 V t≥0. A. (dvC/dt)+100vC= -10u(t) B. (dvC/dt)+1000vC= -10u(t) C. (dvC/dt)+100vC= 10u(t) D. (dvC/dt)+1000vC= 10u(t) E. (dvC/dt)+1000vC= 20000u(t)
Solution: vC(t)= - 20e-1000t+20 V RC-circuit with step-response. General equation is
with general solution of the form vC(t)=[vC(0) – vC(∞)]e-t/Tc + vC(∞) vA=vC(∞)=20V TC=RTC=1/1000; Thus we have
Answer: E.
95. When we transform the circuit from time domain into S-domain the capacitor must be represented as A. capacitor admittance and current source, which is connected with the capacitor in parallel B. capacitor impedance and current source, which is connected with the capacitor in series C. capacitor impedance and voltage source, which is connected with the capacitor in series D. capacitor impedance and voltage source, which is connected with the capacitor in parallel E. A and C are both correct
Solution: 1) 2)
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; 
Multiplying by 1000 gives
Capacitor impedance and voltage source, which is connected with the capacitor in series;
Capacitor admittance and current source, which is connected with the capacitor in parallel.
