Find the potential difference between points $x$ and $y$.

$A$ hollow metal sphere has a radius $r$. The potential difference between a point on its surface and a point at a distance $3r$ from its center is $V$. The electric intensity at the distance $3r$ from the center of the sphere will be

$27$ identical drops are charged at $22 \ V$ each. They combine to form a bigger drop. The potential of the bigger drop will be............ $V$.

When we touch the terminals of a high voltage capacitor,even after the power supply has been disconnected,the capacitor has a tendency to:

While working on a physics project at a school physics lab,you require a $4 \,\mu F$ capacitor in a circuit across a potential difference of $1 \,kV$. Unfortunately,$4 \,\mu F$ capacitors are out of stock in your lab,but $2 \,\mu F$ capacitors which can withstand a potential difference of $400 \,V$ are available in plenty. If you decide to use the $2 \,\mu F$ capacitors in place of the $4 \,\mu F$ capacitor,what is the minimum number of capacitors required?

Three uncharged capacitors of capacitances $C_1$,$C_2$,and $C_3$ are connected as shown in the figure. If $A$,$B$,and $C$ are at potentials $V_1$,$V_2$,and $V_3$ respectively,then the potential at point $O$ is: