$A$ tiny $0.50\, g$ 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

The maximum value of the electric field on the axis of a charged ring having charge $Q$ and radius $R$ is:

Three charges $2q, -q$ and $-q$ are located at the vertices of an equilateral triangle. At the center of the triangle,

Electric field strength due to a point charge of $5\,\mu C$ at a distance of $80\, cm$ from the charge is:

Two point charges $-q$ and $+q/2$ are situated at the origin $(0, 0, 0)$ and at the point $(a, 0, 0)$ respectively. The point along the $X$-axis where the electric field vanishes is:

The charge distribution along the semi-circular arc is non-uniform. The charge per unit length $\lambda$ is given as $\lambda = \lambda_0 \sin \theta$,with $\theta$ measured as shown in the figure. $\lambda_0$ is a positive constant. The radius of the arc is $R$. The electric field at the center $P$ of the semi-circular arc is $E_1$. The value of $\frac{\lambda_0}{\epsilon_0 E_1 R}$ is