$125$ identical drops each charged to the same potential of $50\;volts$ are combined to form a single drop. The potential of the new drop will be......$V$

Write an equation for potential due to a system of charges

Two spheres $A$ and $B$ of radius $a$ and $b$ respectively are at same electric potential. The ratio of the surface charge densities of $A$ and $B$ is

Two charges $3 \times 10^{-8}\; C$ and $-2 \times 10^{-8}\; C$ are located $15 \;cm$ apart. At what point on the line joining the two charges is the electric potential zero? Take the potential at infinity to be zero.

A uniform electric field of $400 \,v/m$ is directed $45^o$ above the $x$ - axis. The potential  difference $V_A - V_B$ is -.....$V$

A charge $+q$ is fixed at each of the points $x = x_0,\,x = 3x_0,\,x = 5x_0$, .... upto $\infty $ on $X-$  axis and charge $-q$ is fixed on each of the points $x = 2x_0,\,x = 4x_0,\,x = 6x_0$, .... upto $\infty $ . Here $x_0$ is a positive constant. Take the potential at a point due to a charge $Q$ at a distance $r$ from it to be $\frac{Q}{{4\pi {\varepsilon _0}r}}$. Then the potential at the origin due to above system of charges will be