The unit of intensity of electric field is

An observer at rest experiences an electric field due to a static charge. Later,he starts moving away from it. What does the observer experience?

$A$ half ring of radius $R$ has a linear charge density of $\lambda$. The electric force on a $1\, C$ charge placed at the centre is

$A$ charge of $1 \mu C$ each is placed on five corners of a regular hexagon of side $1 \ m$. The electric field at its centre is . . . . . . $N$/$C$.

There exists an electric field of magnitude $E$ in the $x$-direction. If the work done in moving a charge of $0.2 \, C$ through a distance of $2 \, m$ along a line making an angle $60^{\circ}$ with the $x$-axis is $4 \, J$,then the value of $E$ is ........ $N / C$.

The variation of electric field along the $Z$-axis due to a uniformly charged circular ring of radius '$a$' in the $XY$ plane is shown in the figure. The value of coordinate $M$ will be