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Concepts Of Physics MCQ Edition [Volume 2]PhysicsElectric Current in Conductors

By evaluating i^2 R , dt , determine how the energy dissipated as heat relates to the energy stored in the capacitor when it is charged by connecting it to a battery via a resistor.

Options

  1. AThe energy dissipated as heat is zero.
  2. BThe energy dissipated as heat is twice the energy stored in the capacitor.
  3. CThe energy dissipated as heat is half the energy stored in the capacitor.
  4. DThe energy dissipated as heat equals the energy stored in the capacitor.

Correct answer

D. The energy dissipated as heat equals the energy stored in the capacitor.

Step-by-step solution

Let the capacitance be C , resistance be R , and the voltage of the battery be V . The current in the circuit at any time t during charging is given by: i = V R e^ -t/RC The energy dissipated as heat across the resistor is: H = ₀^ i^2 R , dt Substituting the expression for i : H = ₀^ ( V R e^ -t/RC )^2 R , dt H = V^2 R ₀^ e^ -2t/RC , dt H = V^2 R [ e^ -2t/RC -2/RC ]₀^ H = V^2 R ( 0 - ( - RC 2 ) ) H = 1 2 C V^2 The energy stored in the capacitor when fully charged is: U = 1 2 C V^2 Thus, the energy dissipated as hea

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