Question

How fast can a capacitor charge?

Answer 1

A capacitor is an electronic component used to store energy in the form of an electric field. It is used in those electronic devices which need a large amount of energy to start initially. A capacitor connected to a battery in a circuit charges till the time the voltage across the capacitor is developed and gets equal to the voltage of the battery.

Complete answer:
Generally, charging a capacitor fully takes infinite time.
While discussing the charging and discharging of a capacitor, we must know about a term called the time constant. The time constant of a capacitor is defined as the product of resistance and capacitance of the capacitor. The capacitor charges to $63\%$ in one constant of time of the capacitor. To charge the capacitor by $99\%$ , a time of five times constant is taken. But after $99\%$ charging capacitor takes infinite time to fully charge.
Hence, the time taken to charge the capacitor by $99\%$ is five times its time constant, but to charge it fully will take infinite time.

Note:
Suppose the capacitance of a capacitor is $200\mu F$, the resistance across the circuit is $2k\Omega$, and the battery of $5V$. Then the time taken to charge this capacitor $99\%$ is calculated below. Time $= 5\left( {200\mu \times 2k} \right) = 2\sec$
So the time taken to charge it by $99\%$ is only two seconds but after this time taken to charge the remaining 1% takes infinite. Or we can say that the capacitor can never be charged $100\%$ .