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Potential Difference Across Capacitor in Steady State Circuit

Under steady state condition the potential difference across the capacitor in the circuit is _____ V.

Question Diagram 1

Options

A

0.5

Correct
B

1.5

C

0

D

2

Step-by-Step Solution

To find the potential difference across the capacitor in the steady state, we analyze the circuit as follows:

1. Steady-State Behavior of the Capacitor

In a DC circuit under steady-state conditions, a capacitor acts as an open circuit. Therefore, no current flows through the branch containing the capacitor: IC=0I_C = 0

2. Potential at the Nodes

Let the common junction on the right side, where all three horizontal branches meet, be chosen as the reference node with potential: Vright=0 VV_{\text{right}} = 0\text{ V}

Since no current flows through the top resistor (Rtop=2 ΩR_{\text{top}} = 2\ \Omega), there is no potential drop across it: Vtop-leftVright=Itop×Rtop=0×2 Ω=0 VV_{\text{top-left}} - V_{\text{right}} = I_{\text{top}} \times R_{\text{top}} = 0 \times 2\ \Omega = 0\text{ V} Vtop-left=Vright=0 VV_{\text{top-left}} = V_{\text{right}} = 0\text{ V}

3. Current in the Active Loop

The remaining part of the circuit forms a single closed loop consisting of:

  • The battery of emf E=2 VE = 2\text{ V}
  • The middle resistor Rmiddle=2 ΩR_{\text{middle}} = 2\ \Omega
  • The bottom resistor Rbottom=6 ΩR_{\text{bottom}} = 6\ \Omega

The total resistance of this loop is: Rtotal=Rmiddle+Rbottom=2 Ω+6 Ω=8 ΩR_{\text{total}} = R_{\text{middle}} + R_{\text{bottom}} = 2\ \Omega + 6\ \Omega = 8\ \Omega

The steady-state current II flowing through this loop is given by Ohm's law: I=ERtotal=2 V8 Ω=0.25 AI = \frac{E}{R_{\text{total}}} = \frac{2\text{ V}}{8\ \Omega} = 0.25\text{ A}

4. Potential at the Middle-Left Node

The potential difference across the middle resistor is: Vmiddle-leftVright=I×Rmiddle=0.25 A×2 Ω=0.5 VV_{\text{middle-left}} - V_{\text{right}} = I \times R_{\text{middle}} = 0.25\text{ A} \times 2\ \Omega = 0.5\text{ V}

Since Vright=0 VV_{\text{right}} = 0\text{ V}, we have: Vmiddle-left=0.5 VV_{\text{middle-left}} = 0.5\text{ V}

5. Potential Difference Across the Capacitor

The capacitor is connected between the top-left node and the middle-left node. Thus, the potential difference across the capacitor VCV_C is: VC=Vtop-leftVmiddle-left=0 V0.5 V=0.5 VV_C = |V_{\text{top-left}} - V_{\text{middle-left}}| = |0\text{ V} - 0.5\text{ V}| = 0.5\text{ V}

Thus, the potential difference across the capacitor in steady state is 0.5 V.

Correct Option: A

Potential Difference Across Capacitor in Steady State Circuit | Physics PYQ Solution - JEE Challenger