Rankers Physics
Topic: Capacitors
Subtopic: Charging and Discharging of Capacitors

In the circuit shown in the figure, the switch S is initially open and the capacitor is initially uncharged. I1, I2 and I3 represent the current in the resistance 2Ω, 4Ω and 8Ω respectively. Image related to
Just after the switch S is closed, I1 = 3A, I2 = 3A and I3 = 0
Just after the switch S is closed, I1 = 3A, I2 = 0 and I3 = 0
long time after the switch S is closed, I1 = 0.6 A, I2 = 0 and I3 = 0
long after the switch S is closed, I1 = I2 = I3 = 0.6 A.

Solution:

Here's the short solution for the circuit:

  1. Just after the switch is closed:
    • The capacitors act as open circuits because they are initially uncharged (capacitor voltage cannot change instantaneously).
    • This means no current flows through the branches containing the capacitors.
  2. Current Distribution:
    • The total resistance in the circuit is only the sum of the resistors in the main loop (2Ω + 8Ω), as the branches with capacitors are effectively open.
    • Total resistance =
      2Ω+8Ω=10Ω2\Omega + 8\Omega = 10\Omega
       

      .

    • Current
      I1=VoltageResistance=6V2Ω+8Ω=0.6AI_1 = \frac{\text{Voltage}}{\text{Resistance}} = \frac{6V}{2\Omega + 8\Omega} = 0.6A
       

      .

  3. Branch currents:

    • I3=0I_3 = 0
       

      since the capacitor branch is open.


    • I2=0I_2 = 0
       

      for the same reason as above.

Final Answer:

  • \( I_1 = 0.6 A, \ I_2 = 0\)

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