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MHT CET 2025 (21 Apr, Shift 2) · Energy Stored & Force between Plates

Energy Stored & Force between Plates question from MHT CET 2025 (21 Apr, Shift 2)

Q10MHT CET 2025 · 21 APR · SHIFT 2Medium

Energy Stored & Force between Plates

A parallel plate capacitor having plate area ' AA ' and separation ' dd ' is charged to a potential difference ' VV '. The charging battery is disconnected and the plates are pulled apart to four times the initial separation. The work required to increase the distance between the plates is ( ε0=\varepsilon_0 = permittivity of free space)

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Answer: (d)

  1. Battery disconnected: QQ constant, U=Q22CU = \frac{Q^2}{2C}.
  2. d→4d⇒C→C4d \to 4d \Rightarrow C \to \frac{C}{4}, so Uf=4UiU_f = 4U_i.
  3. W=Uf−Ui=3Ui=3×12ε0AdV2W = U_f - U_i = 3U_i = 3 \times \frac{1}{2}\frac{\varepsilon_0 A}{d}V^2
  4. So the answer is (d) 3ε0AV22d\frac{3\varepsilon_0 AV^2}{2d}.
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