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KCET2013PhysicsCapacitance

When an additional charge of 2 C is given to a capacitor, energy stored in it is increased by 21 % . The original charge of the capacitor is

Options

  1. A30 C
  2. B40 C
  3. C10 C
  4. D20 C

Correct answer

D. 20 C

Step-by-step solution

Energy stored by a capacitor, U= 1 2 q² C So, here U₁= 1 2 q₁² C ; U₂= 1 2 q₂² C U₁ U₂ = ( q₁ q₂ )²= ( q q+2 )² Given, U₂-U₁ U₁ =0.21 or U₂ U₁ =1.21 ( q q+2 )²=1.21 On solving we, get q=20 C

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