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Asked in MDCAT Test Series — Electrostatics, Work and Energy

For a parallel plate capacitor, the energy density is:

Correct answer: B. ½ ε₀.εᵣ.E2

  • A. ½ εᵣ.ε₀.E
  • B. ½ ε₀.εᵣ.E2
  • C. ε₀.εᵣ.E
  • D. ε₀.εᵣ.E2

Explanation

Energy density is the total energy per unit volume of the capacitor, as the electrostatic energy stored in a parallel plate capacitor is U=½ CV2for a parallel plate capacitor, C=(ε0εrA)/d and V = Ed; so,U=½ (ε0εrA/d)(Ed)2=½ ε0εrE2(Ad),Where Ad = Volume of the capacitor (V). ThenEnergy density U/V = ½ ε0εrE2.

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About Capacitors

Capacitors store electric charge and energy in an electric field between conductors. Work includes capacitance, the relation Q = CV, dielectric materials, charging and discharging, energy formulas, and combinations of capacitors in series and parallel. Electric potential difference is needed to understand why charge and stored energy change.

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