The equipotential curves in $x\text{,} y$ plane are given by $V=x^2+y^2-4x+4$ where $V$ is potential. Draw the rough sketch of electric field lines in $x-y$ plane.

A uniform electric field exists in $xy$ plane as shown in the figure. Find the potential difference between the origin $O$ and $A\left(d, d, 0\right)$.

Four balls, each with mass $m$, are connected by four non-conducting strings to form a square with side $a$, as shown in the figure. The assembly is placed on a horizontal non-conducting frictionless surface. Balls $1$ and $2$ each have charge $q$ and the balls $3$ and $4$ are uncharged. Find the maximum speed of balls $1$ and $2$ after the string connecting them is cut.

Consider the configuration of a system of four charges each of value $+q$. Find the work done by external agent in changing the configuration of the system from figure (a) to figure (b).

Charges $+q$ and $-q$ are located at the corners of a cube of side as shown in the figure. Find the work done to separate the charges to infinite distance.

Four point charges $q, q, q$ and $-q$ are placed at the vertices of a square of side length $a$ as shown in Figure below. The arrangement is changed and the charge are positioned at the vertices of a rhombus of side length $a$ with $-q$ charge at the vertex where angle is $120°$ as shown in the second figure below. Find the work done by the external agent is changing the configuration.