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CAIE A-Level Physics 19.3.1 Capacitor Discharge Graphs

Practise analysing how potential difference, charge and current change during capacitor discharge, identifying exponential decay and relating graphs to circuit behaviour.

Syllabus
2028–2030
Course
Physics 9702
Level
A2

Exam points

  • analyse time graphs of potential difference, charge and current while a capacitor discharges through a resistor
  • identify exponential decay, initial values, signs and relative rates from discharge graphs
  • relate the decay of current, charge and potential difference to the circuit behaviour

19.3.1—The variation with time of potential difference, charge and current question 1

[Maximum number: 2]

A capacitor of capacitance 470μ F470 \mu \mathrm{~F} is connected to a battery of electromotive force (e.m.f.) 24 V in the circuit of Fig. 5.1.

Fig. 5.1

Fig. 5.1

The two-way switch S is initially at position X.
P and Q are identical long straight wires, each with a resistance of 5.6kΩ5.6 \mathrm{k} \Omega. These wires are placed near to, and parallel to, each other. Wire Q is connected to a voltmeter.

At time t=0, switch S is moved to position Y so that the capacitor discharges through wire P .

On Fig. 5.2, sketch a line to show the variation with t of the current I in wire P as the capacitor discharges.

Fig. 5.2

Fig. 5.2

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