Question

The charging time constant of a circuit consisting of a capacitor is the time taken for the charge in the capacitor to become __________ % of the initial charge.

(a) 33

(b) 63

(c) 37

(d) 36

This question was addressed to me in an online quiz.

My query is from Growth and Decay in chapter Capacitance and Capacitors of Basic Electrical Engineering

Answer 1

Right option is (b) 63

The best I can explain: We know that: Q=Q0(1-e^-t/RC).

When RC=t, we have: Q=Q0(1-e^-1) = 0.63*Q0.

Hence the time constant is the time taken for the charge in a capacitive circuit to become 0.63 times its initial charge.