The switches S1 and S2 in the figure are initially open (as shown), and the capa

Question

The switches S1 and S2 in the figure are initially open (as shown), and the capacitors are initially uncharged. Then, at time t = 0, both switches are closed. Assume VB = 18 V, R1 = 100hm, R2 = 20Ohm, R1 = 30Ohm, C1 = 10muF, C2 = 20muF, and C3 = 30muF. What is the current through the resistor R1 immediately after the switches are closed? What is the current through resistor R: a very long time after the switches are closed? What is the charge on the capacitor C2 a very long time after the switches are closed?

Explanation / Answer

a)

Immediately after switch cloesd ,all capacitors acts as short circuit ,so current flows through least resistive path

.Current flowing through R1 is

I1=Vb/R1=18/10

I1=1.8 A

b)

After very long time switches are closed ,all capacitors act as open circuit

I2=0 A

c)

Total current flowing in the circuit is

I=Vb/(R1+R3) =18/(10+30) =0.45 A

Voltage across R3 is

V3=I*R3=0.45*30 =13.5 Volts

Charge across C2 is

Q2=V3C2 =20u*13.5

Q2=270 uC or 2.7*10-4C

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