Why Capacitor Discharge Slows Down
Why Capacitor Discharge Slows Down
- Connect a charged capacitor across a resistor. Charge, p.d. and current magnitude then fall exponentially.
Follow the causal chain
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- Less remaining charge gives a smaller capacitor p.d.
- The resistor has the same smaller p.d. across it.
- The current is therefore smaller.
- Charge leaves more slowly, so the graph becomes flatter.
This is the full three-mark explanation in a recent mark scheme (9702/43/M/J/24 Q6(a)).
Read the exponential graph
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- Charge and p.d. stay positive and approach zero.
- A current graph may show signed current or its positive magnitude. Read the axis label before choosing a sign.
- The ideal curve does not reach zero at a finite time.
Your turnquick check
Why does the discharge graph become flatter as time increases?
Show worked answer
Less charge gives a smaller p.d. and current, so charge leaves more slowly.