Switch S is closed at time t = 0 foe the circuit sown at right- Before the switc
ID: 1485333 • Letter: S
Question
Switch S is closed at time t = 0 foe the circuit sown at right- Before the switch closed all the capacitors were empty, (not charged at all). C = 0.3 F. R = 100 Ohm and epsilon = 15 V. Find the current I at time t = 0 and after very long time later (t = infinity), meaning when the capacitors are fully charged. What is the characteristic time, tau? In how many minutes will the capacitors be charged fully? Use our 3r criteria as usual. Switch S is closed at time t = 0 for the circuit sown at right. L = 8H.R = 200 Ohm and epsilon = 120 V, find the current I at time t = 0 and after very long time later (t = infinity). What is the characteristic time, tau? In how many seconds will the current reach its maximum value? Use our 3r criteria as usual.Explanation / Answer
3) (a) at t=0 capacitors will behave as a short circuit
=> current I=E/R = 15/100 =0.15 A
(b) at t=infinite capacitors will behave as a open circuit
=> current I = 0 A
(c) charactristic time T= RCeq
T = R*[(2C*C)/(2C+C)]=2R*C/3 =2*100*0.3/3 = 20 sec
equivalent capacitance = (2C*C)/(2C+C)=2C/3 = 2*0.3/3 =0.2F
(d) capacitor will take 3T sec which is = 3*20 =60 sec=1 min.
4) (a) at t=0 inductor will behave as a open circuit
=> current I= 0A
(b) at t=infinite inductor will behave as a short circuit
=> current I=E/R=120/200=0.6 A
(c) charactristic time T=Leq/R= [(L*L)/2L]/R=(8/2)/200=0.02 sec
Leq = L*L/2L=L/2=8/2 = 4H
(d) circuit will take 3T sec to reach max value
= 3*0.02=0.06 sec
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