NVAMediumJEE 2023Capacitors & Dielectrics

JEE Physics 2023 Question with Solution

In the Provided that circuit, C1=2μFC_1 = 2 \, \mu\text{F}, C2=0.2μFC_2 = 0.2 \, \mu\text{F}, C3=2μFC_3 = 2 \, \mu\text{F}, C4=4μFC_4 = 4 \, \mu\text{F}, C5=2μFC_5 = 2 \, \mu\text{F}, C6=2μFC_6 = 2 \, \mu\text{F}. The charge stored on capacitor C4C_4 is _____ μC\mu\text{C}.

Answer

Correct answer:4

Step-by-step solution

Standard Method

Given: The solution states that the total equivalent capacitance is 0.5μF0.5 \, \mu\text{F} and the applied voltage is 10V10 \, \text{V}.

Find: The charge stored on capacitor C4C_4.

Using the equivalent capacitance, the total charge in the circuit is

Q=CeqVQ = C_{\text{eq}} \cdot V

Substituting the values given in the solution:

Q=0.5×10=5μCQ = 0.5 \times 10 = 5 \, \mu\text{C}

Now use the charge division relation quoted in the solution for the relevant branch:

Q=QC2C2+C6Q' = Q \cdot \frac{C_2}{C_2 + C_6}

The solution substitutes:

Q=50.80.8+0.2Q' = 5 \cdot \frac{0.8}{0.8 + 0.2}

So,

Q=50.8=4μCQ' = 5 \cdot 0.8 = 4 \, \mu\text{C}

Therefore, the charge stored on capacitor C4C_4 is 4μC4 \, \mu\text{C}. Hence the numerical answer is 4.

Note: The extracted solution contains an internal inconsistency because the question states C2=0.2μFC_2 = 0.2 \, \mu\text{F}, while the working uses 0.8μF0.8 \, \mu\text{F} in the charge division step. However, the solution concludes the final value as 4μC4 \, \mu\text{C}, and that is taken as the answer.

Common mistakes

  • Using the given capacitor values directly in a random series-parallel reduction without identifying the branch for charge division is incorrect. First determine the equivalent charge flow in the circuit, then apply the branch relation used in the solution.

  • Confusing capacitance with charge is incorrect because Q=CVQ = CV depends on both capacitance and potential difference. A capacitor with larger capacitance does not automatically have the same charge unless the voltage condition is also known.

  • Ignoring inconsistencies in the extracted working can lead to a wrong result. Here the solution uses C2=0.8μFC_2 = 0.8 \, \mu\text{F} although the question states 0.2μF0.2 \, \mu\text{F}, so the final answer must be taken from the concluded solution value rather than mixing both datasets.

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