Question

The capacitor ' $C ^{\prime}$ is initially uncharged. Switch $S _{1}$ is closed for a long time while $S _{2}$ remains open. Now at $t=0, S_{2}$ is closed while $S_{1}$ is opened. All the batteries are ideal and connecting wires are resistanceless. Find INCORRECT statement :

• A. At time $t=0$ (just after $S_{2}$ is closed), reading of ammeter is $\frac{ E }{5 R }$
• B. At time $t=0$ (just after $S_{2}$, is closed), reading of ammeter is zero
• C. Heat developed till time $t=5 RCln 2$ in resistance $3 R$ is $\frac{9}{40} C E^{2}$
• D. After time $t>0$ charge on the capacitor follows the equation $CEe ^{- t / 5 RC }$

Answer 1

Answer: (B)

$i=\frac{E}{5 R}$
equation of charge of capacitor
$q = CEe ^{-t / \tau }$
$q = ECe ^{- t/5RC }$
at $t =5\, RC\, \ln 2$
$q =\frac{ EC }{2}$