19.3.1—The variation with time of potential difference, charge and current
- Syllabus
- 9702–2028–2029
- Objective
- 19.3.1
- Level
- A2
During capacitor discharge, voltage and charge fall while current follows the changing rate of charge
A discharging capacitor has decreasing Q and V; current is related to the rate of charge change and initially has the greatest magnitude.
Use the circuit polarity and current direction consistently. The resistor receives energy as the capacitor’s electric field collapses.
A voltage-time trace falls steeply at first and then levels off, showing that the discharge rate slows.
Current is not constant during discharge, and a falling voltage does not mean the capacitor instantly becomes uncharged.
ConceptA-Level CAIE Physics A2