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NEET2017PhysicsCapacitanceActual

A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system

Options

  1. Aincreases by a factor of 4 .
  2. Bdecreases by a factor of 2 .
  3. Cremains the same.
  4. Dincreases by a factor of 2 .

Correct answer

B. decreases by a factor of 2 .

Step-by-step solution

Charge on capacitor, q = C V When it is connected with another uncharged capacitor. V c = q 1 + q 2 C 1 + C 2 = q + 0 C + C V c = V 2 Initial energy, U i = 1 2 C V 2 Final energy, U f = 1 2 C V 2 2 + 1 2 C V 2 2 = C V 2 4 Loss of energy = U i - U f = C V 2 4 , i.e., decreases by a factor of 2 .

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