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3 marksCapacitors

CAPE Physics Unit 2 · 2001 · Paper 1 · Question 3(c)(ii)

A parallel-plate capacitor with A = 20.0 cm² and plate separation d = 4.5 mm in an electric field of strength E = 3 × 10⁶ V m⁻¹.

Calculate the energy per unit volume, U.

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Other parts of this question

  1. 3(a)Define 'capacitance'.[1 mark]
  2. 3(b)(i)Write a formula for the capacitance of a parallel plate air capacitor in terms of the area of the plates, A, and their distance apart, d.[1 mark]
  3. 3(b)(ii)Hence show that the energy per unit volume, U, of the capacitor is given by U = (ε₀ E²) / 2, where ε₀ is the permittivity of free space.[3 marks]
  4. 3(c)(i)Calculate the capacitance in air.[2 marks]

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