Capacitors require a resistor to discharge because they store electrical energy in the form of an electric field between two conductive plates separated by a dielectric material.
Would a capacitor discharge almost instantaneously?
Hence, our final answer is that the capacitor would discharge almost instantaneously. The diagram shows a circuit containing a capacitor and a resistor. The capacitor is discharging, and there is an electric current through the circuit. What would happen if a capacitor were allowed to discharge through the same circuit, but without the resistor?
And hence, through this circuit without any resistor, the capacitor would be allowed to discharge almost instantaneously. It would happen very very quickly.
Can a resistor be added to a capacitor?
You should realise that the addition of a resistor in the circuit in series with the capacitor ONLY affects the TIME it takes for the capacitor to become fully charge and NOT the EVENTUAL POTENTIAL DIFFERENCE ACROSS IT – this is always the same and equal to the potential difference across the supply. (Figure 1)
You could in theory use an inductor to discharge a capacitor, but oscillation may reverse the voltage and so destroy a polarised dielectric such as a tantalum capacitor. So avoid shorting capacitors, use a resistor when possible.
What happens when a capacitor is opened in a circuit?
As switch S is opened, the capacitor starts to discharge through the resistor R and the ammeter. At any time t, the p.d. V across the capacitor, the charge stored on it and the current (I), flowing through the circuit and the ammeter are all related to each other by two equations.
What happens if a capacitor plate is connected to a resistor?
Similarly, if the capacitor plates are connected together via an external resistor, electrons will flow round the circuit, neutralise some of the charge on the other plate and reduce the potential difference across the plates. The same ideas also apply to charging the capacitor.