A charged capacitor is connected across a resistor, the pd creates a current through the circuit. This current flows in the opposite direction to the charging current. If there is a voltmeter in the circuit, you can observe the decrease in voltage. When the p.d. across the plates is zero, the capacitor is fully discharged.

The time it takes to charge or discharge a capacitor depends on two things:

1) The capacitance of the capacitor. This affects the charge that can be transferred at a certain voltage.

2) The resistance of the circuit. This affects the current

A capacitor discharges exponentially with time. This means that no matter the charge, it takes the same length of time for the charge to halve. The graphs of V against t, and l against t for charging and discharging are also exponential

Q = Q0e ^ (- t / RC)

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