Question

The time constant of an $R-C$ circuit during discharge is that time in which charge on condenser plates, as compared to maximum charge $\left(q_0\right)$, becomes:

• A. $63.3\%$
• B. $36.3\%$
• C. $50\%$
• D. $25\%$

Answer 1

The correct option is B $36.3\%$

During discharging of capacitor,
$q=q_o{e}^{\frac{-t}{\tau }}$
when $t=\tau$
$q=q_o{e}^{-1}$
$q=q_o\times 0.363$
$q$ equals to $36.3$% of $q_o$
therefore,option (B) is correct