Fig 9Charging a capacitorclick to pausecharging: 0%
A capacitor is two conducting plates separated by an insulator. Connect it to a battery and charge piles up on the plates, positive on one and negative on the other, so a voltage builds between them that pushes back against the battery. The more it charges, the harder it pushes back and the more slowly charge arrives, so the voltage rises quickly at first and then levels off. After one time constant, the resistance times the capacitance (RC), it reaches 63% of the battery voltage, and after five it is effectively full.