In: Physics
How might you set up a circuit that charges a capacitor slowly, then releases its charge quickly in a large current? How might a capacitor be used in a circuit to prevent sudden spikes in voltage? When the capacitor is fully charged, how does the voltage between its plates compare that of the power supply’s? What does this mean about the voltage across the resistor? In turn, what does that mean about the current through the circuit?
Ans.
You can have circuit with a two way switch such that when the switch is in first position(it's series RC circuit, charged by a battery) the circuit charges through a large resistor (large time constant hence takes longer time to charge) and then we move to the switch to other position( its a series RC circuit no battery) which has small resistor, so that it has small time constant and larger current through the circuit.
Since a capacitor does not like sudden change in the voltage across it, hence they can be used to protect a circuit from sudden spikes in voltage.
When a capacitor is fully charged in a series RC circuit, the voltage across the capacitor is equal to the voltage of the power supply. Since all the voltage of the supply is now across the capacitor, hence the voltage across the resistor is zero. Since the voltage across the resistor is zero. Hence the current in the circuit is zero.