Electric field at centre $O$ of semicircle of radius $a$ having linear charge density $\lambda$ given is given by
$\frac{\lambda }{{2\pi {\varepsilon _0}a}}$
$\frac{\lambda }{{2\pi {\varepsilon _0}{a^2}}}$
$\frac{\lambda }{{4{\pi ^2}{\varepsilon _0}a}}$
$\frac{{{\lambda ^2}}}{{2\pi {\varepsilon _0}a}}$
A tiny $0.50\, gm$ ball carries a charge of magnitude $10\, \mu C$. It is suspended by a thread in a downward electric field of intensity $300\, N/C$. If the charge on the ball is positive, then the tension in the string is
Infinite charges of magnitude $q$ each are lying at $x =1,\, 2,\, 4,\, 8...$ meter on $X$-axis. The value of intensity of electric field at point $x = 0$ due to these charges will be
In the given figure distance of the point from $A$ where the electric field is zero is......$cm$
A ring of radius $R$ is charged uniformly with a charge $+\,Q$ . The electric field at a point on its axis at a distance $r$ from any point on the ring will be
The point charges $Q$ and $-2Q$ are placed at some distance apart. If the electric field at the location of $Q$ is $\vec E$ , then the electric field at the location of $-2Q$ will be :