Figure shows the variation of electric field intensity $E$ versus distance $x$. What is the potential difference between the points at $x=2 \,m$ and at $x=6 \,m$ from $O$ is ............. $V$

At a certain distance from a point charge, the field intensity is $500\, Vm^{-1}$ and the potential is $-3000\, V$. The distance to the charge and the magnitude of the charge respectively are

An infinite number of charges each equal to $0.2\,\mu C$ are arranged in a line at distances $1\,m, 2\,m, 4\,m, 8\,m......$ from a fixed point. The potential at fixed point is ......$kV$

Ten charges are placed on the circumference of a circle of radius $R$ with constant angular separation between successive charges. Alternate charges $1,3,5,7,9$ have charge $(+q)$ each, while $2,4,6,8,10$ have charge $(-q)$ each. The potential $V$ and the electric field $E$ at the centre of the circle are respectively

(Take $V =0$ at infinity $)$

Point charge ${q_1} = 2\,\mu C$ and ${q_2} = - 1\,\mu C$ are kept at points $x = 0$ and $x = 6$ respectively. Electrical potential will be zero at points

Two insulated charged conducting spheres of radii $20\,cm$ and $15\,cm$ respectively and having an equal charge of $10\,C$ are connected by a copper wire and then they are separated. Then