Question

What is the time constant?

Answer 1

C

Explanation:

When a capacitor `C` initially having charge `Q_0` discharges through a resistor `R`, the discharge follows a decay curve as

`Q=Q_0e^(-t//tau)`
where time constant `tau=RC` and `Q` is charge remaining on the capacitor after time `t`

Putting `t=tau`, we get

`Q=Q_0e^(-tau//tau)`
`=>Q=Q_0/e`