Points $A$ and $B$ are separated by $3 \mathrm{cm}$ and a uniform electric field is acting from $A$ to $B$ with $\mathrm{E}=300 \mathrm{N} {\mathrm{C}}^{-1}.$ A charge of $3 \mu \mathrm{C}$ is taken from $B$ to $A.$ Force acting on the $3 \mu \mathrm{C}$ charge is ________

Two point charges $\frac{+q}{2}$ and $-q$ are placed at a point $(\mathrm{a}, 0, 0)$ and at origin respectively. The point along the $x$-axis where the electric field vanishes is $\underline{ }$

The variation of electric potential with distance from a fixed point is shown in the figure. What is the value of electric field at $x=2 \mathrm{m}?$