$A$ point charge of $10\,\mu C$ is placed at the origin. At what location on the $X$-axis should a point charge of $40\,\mu C$ be placed so that the net electric field is zero at $x = 2\,cm$ on the $X$-axis?

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

Four charges $+q, +2q, +q$ and $-2q$ are placed at the corners $A, B, C$ and $D$ of a square respectively. The force on a unit positive charge kept at the centre $O$ is

$A$ positively charged ball hangs from a silk thread. We put a positive test charge $q_0$ at a point and measure $F/q_0$. Then, it can be predicted that the electric field strength $E$ is:

Two charged thin infinite plane sheets of uniform surface charge density $\sigma_{+}$ and $\sigma_{-}$ where $\left|\sigma_{+}\right|>\left|\sigma_{-}\right|$ intersect at a right angle. Which of the following best represents the electric field lines for this system?

$A$ point charge $+q$ is placed at the origin. $A$ second point charge $+9q$ is placed at $(d, 0, 0)$ in a Cartesian coordinate system. The point in between them where the electric field vanishes is: