Question

The time constant of the show circuit for charging is

• A. $\frac{5}{3}RC$
• B. $\frac{5}{2}RC$
• C. $\frac{7}{4}RC$
• D. $\frac{3}{7}RC$

Answer 1

The correct option is D $\frac{3}{7}RC$

Resultant Resistance

$\Rightarrow 2R+1R=3R$

Now, $\frac{1}{RC}=\frac{1}{3}R+R+R\frac{1}{RC}=\frac{1R+3R+3R}{3}\frac{1}{RC}=\frac{7R}{3}RC=\frac{3}{7}R$

Now the time constant $=\frac{3}{7}RC$

$\because \tau =RC$