Four identical capacitors are connected in series with a battery of $emf$ $10\,V$. The point $X$ is earthed, then the potential of point $A$ is.....$V$

A parallel plate capacitor of capacitance $C$ is connected to a battery and is charged to a potential difference $V$. Another capacitor of capacitance $2C$ is connected to another battery and is charged to potential difference $2V$ . The charging batteries are now disconnected and the capacitors are connected in parallel to each other in such a way that the positive terminal of one is connected to the negative terminal of the other. The final energy of the configuration is

The work done required to put the four charges together at the corners of a square of side $a$ , as shown in the figure is

A thin spherical conducting shell of radius $R$ has a charge $q.$ Another charge $Q$ is placed at the centre of the shell. The electrostatic potential at a point $p$ a distance $R/2$ from the centre of the shell is

A $2\,\mu F$ capacitor is charged as shown in the figure. The percentage of its stored energy dissipated after the switch $S$ is turned to position $2$, is.....$\%$

Side length of equilateral triangle is $d. P$ is mid of side then potential at point $P, V_P$ is