MCQ
In the transient current circuit shown, the time constant is
  • A
    $\frac{5}{3}\,RC$
  • B
    $\frac{5}{2}\,RC$
  • $\frac{7}{4}\,RC$
  • D
    $\frac{7}{3}\,RC$

Answer

Correct option: C.
$\frac{7}{4}\,RC$
c
$r_{e q}=\frac{R \times 3 R}{R+3 R}=\frac{3 R}{4}$

$\mathrm{R}+\mathrm{r}_{\mathrm{eq}}=\mathrm{R}+\frac{3}{4} \mathrm{R}=\frac{7}{4} \mathrm{R}$

$\therefore $ time constant $=\frac{7}{4} \mathrm{RC}$

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