Question

In the circuit shown in the figure, find the amount of heat generates when switch $S$ is closed.

Answer 1

When the switch is open, $q_1+q_2=0$

$(V-5)\times 2+(V+10)\times 4=0$

$V=-5Volts$

so,

$q_1=(-5-5)\times 2=-20\mu C$

$q_2=(-5+10)\times 4=20\mu C$

After the switch is closed,

$q_1$ and $q_2$ will be same,

only the charge will be in $q_3$

$q_3=CV=3\times 10=30\mu C$

So, heat generated=Work done by the battery-Energy stored in capacitor.

$10\times 30-\frac{1}{2}\times 3\times {\left(10\right)}^2$

$=150\mu J$