Question

The figure shows an experiment plot for discharging of a capacitor in an $R-C$ circuit. The time constant $t$ of this circuit lies between

• A. $0and50sec$
• B. $50and100sec$
• C. $100and150sec$
• D. $150and200sec$

Answer 1

The correct option is C $100and150sec$

During discharging of a capacitor $V=V_0{e}^{\frac{–t}{\tau }}$ where $t$ is the time constant of RC circuit.

At $t=\tau$, $V=\frac{V_0}{e}=0.37V_0$

From the graph, $t=0$,$V_0=25$V

$\therefore V=0.37\times 25$V $=9.25$V

This voltage occurs at time lies between $100$sec and $500$sec.

Hence, time constant $\tau$ of this circuit lies between $100$sec and $500$sec.