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NEET 2026
Exam
NEET
Year
2026
Subject
Physics
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Chapter

NEET 2026 · Physics · Chapter

In the given circuit, the two-way switch S is initially kept at...

In the given circuit, the two-way switch S is initially kept at position 1 for a long time, fully charging the
In the given circuit, the two-way switch SS is initially kept at position 1 for a long time, fully charging the capacitor C1=4 μFC_1 = 4\ \mu\text{F} using a 50 V50\ \text{V} battery. The switch is then shifted to position 2, disconnecting the battery and connecting C1C_1 to an initially uncharged capacitor C2=6 μFC_2 = 6\ \mu\text{F}. The amount of electrostatic energy dissipated as heat during the redistribution of charge is:

Options

  1. A2×10−3 J2 \times 10^{-3}\ \text{J}
  2. B3×10−3 J3 \times 10^{-3}\ \text{J}
  3. C5×10−3 J5 \times 10^{-3}\ \text{J}
  4. D1.5×10−3 J1.5 \times 10^{-3}\ \text{J}

Correct answer

B. 3×10−3 J3 \times 10^{-3}\ \text{J}

Step-by-step solution

When the switch is at position 1, capacitor C1C_1 is charged to potential V1=50 VV_1 = 50\ \text{V}.

When the switch is shifted to position 2, C1C_1 is connected across the initially uncharged capacitor C2C_2 (V2=0V_2 = 0).

The electrostatic energy dissipated as heat during the redistribution of charge is given by the formula:

ΔU=12C1C2C1+C2(V1−V2)2\Delta U = \dfrac{1}{2} \dfrac{C_1 C_2}{C_1 + C_2} (V_1 - V_2)^2

Substituting the given values C1=4 μFC_1 = 4\ \mu\text{F}, C2=6 μFC_2 = 6\ \mu\text{F}, V1=50 VV_1 = 50\ \text{V}, and V2=0 VV_2 = 0\ \text{V}:

ΔU=12×(4×10−6)×(6×10−6)(4+6)×10−6×(50−0)2\Delta U = \dfrac{1}{2} \times \dfrac{(4 \times 10^{-6}) \times (6 \times 10^{-6})}{(4 + 6) \times 10^{-6}} \times (50 - 0)^2

ΔU=12×24×10−1210×10−6×2500\Delta U = \dfrac{1}{2} \times \dfrac{24 \times 10^{-12}}{10 \times 10^{-6}} \times 2500

ΔU=12×2.4×10−6×2500\Delta U = \dfrac{1}{2} \times 2.4 \times 10^{-6} \times 2500

ΔU=1.2×10−6×2500\Delta U = 1.2 \times 10^{-6} \times 2500

ΔU=3000×10−6 J\Delta U = 3000 \times 10^{-6}\ \text{J}

ΔU=3×10−3 J\Delta U = 3 \times 10^{-3}\ \text{J}

Answer: 3×10−3 J3 \times 10^{-3}\ \text{J}
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