What this practice covers
These questions are drawn from past CIE 9702 Physics papers and filtered to capacitance. You answer, you find out immediately whether you were right, and you get the reasoning for the correct option and for each distractor. Wrong answers go to a mistakes locker so you can come back to exactly those.
Practice is free. You need an account only so your progress and your mistakes are still there next time.
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What examiners see students get wrong here
These are the errors that cost marks on capacitance, taken from our own topic notes. Read them before you practise and you will recognise the traps in the questions.
- Saying a charged capacitor stores a net charge of Q. It stores +Q and -Q, so the net charge is zero.
- Adding capacitors in series as if they were resistors, and using the reciprocal formula for parallel.
- Getting a series combination larger than one of its components, which is always a sign the formula has been used the wrong way round.
- Forgetting to take the reciprocal at the end of the series calculation.
- Dropping the factor of ½ from W = ½QV.
- Saying the energy supplied by the battery equals the energy stored. Half is dissipated in the circuit resistance.
- Saying doubling the voltage doubles the stored energy. It quadruples it.
- Saying the time constant is the time for the capacitor to discharge completely. An exponential never reaches zero.
Revise it first
If any of the above is unfamiliar, work through the notes before practising: Capacitance revision notes.