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3 marksCapacitors

CAPE Physics Unit 2 · May/June 2026 · Paper 2 · Question 1(d)(i)

A large flat stratus cloud at a height of 1500 m lies parallel to a treeless plain. The cloud extends over an area of 2.5 square kilometres and carries a charge of 20 coulombs. Assuming that air has the permittivity of free space, calculate the capacitance of the system formed by the cloud, air and the ground.

Calculate the capacitance of the system formed by the cloud, air and the ground.

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Other parts of this question

  1. 1(a)Define the term 'capacitance' as it relates to electric circuits.[1 mark]
  2. 1(b)The formula below is used to calculate the capacitance of a parallel plate capacitor: C = εA/d. State the meaning of EACH symbol on the right-hand side of the…[3 marks]
  3. 1(c)Using the formulae to calculate the electric field, E, in a parallel plate capacitor and the charge, Q, on the plates, show that E = (1/ε) * (Q/A).[3 marks]
  4. 1(d)(ii)Calculate the energy stored in the cloud-ground capacitor.[3 marks]
  5. 1(d)(iii)Calculate the value of the electric field in the cloud-ground capacitor.[2 marks]
  6. 1(d)(iv)State how the values calculated in (d) (i), (ii) and (iii) will change if the true value of the permittivity of air was used.[3 marks]
  7. 1(e)(i)Complete Columns 3 and 4 of Table 1.[2 marks]
  8. 1(e)(ii)On the grid provided in Figure 1 on page 9, plot a graph of ln (Q/Q₀) versus t. Draw the line of best fit through the points.[4 marks]
  9. 1(e)(iii)Determine the slope of the graph in (e) (ii) and state what this value represents.[4 marks]
  10. 1(e)(iv)Based on the result obtained in (e) (iii), estimate the duration of the lightning strike.[2 marks]

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