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4 marksCapacitors

CAPE Physics Unit 2 · May/June 2026 · Paper 2 · Question 1(e)(ii)

Under certain atmospheric conditions, the air between the cloud and the ground may become partially ionized and begin conducting current, leading to a lightning strike. Table 1 records the exponential decay of the initial charge, Q₀, from the cloud during such a strike.

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.

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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)(i)Calculate the capacitance of the system formed by the cloud, air and the ground.[3 marks]
  5. 1(d)(ii)Calculate the energy stored in the cloud-ground capacitor.[3 marks]
  6. 1(d)(iii)Calculate the value of the electric field in the cloud-ground capacitor.[2 marks]
  7. 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]
  8. 1(e)(i)Complete Columns 3 and 4 of Table 1.[2 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]

More practice: the rest of this paper · more Capacitors questions · all CAPE Physics Unit 2 past papers