A charged particle having some mass is resting in equilibrium at a height $H$ above the centre of a uniformly charged non-conducting horizontal ring of radius $R$. The force of gravity acts downwards. The equilibrium of the particle will be stable $R$
for all values of $H$
only if $H >$ $\frac{R}{{\sqrt 2 }}$
only if $H <$ $\frac{R}{{\sqrt 2 }}$
only if $H =$ $\frac{R}{{\sqrt 2 }}$
$(a)$ Two insulated charged copper spheres $A$ and $B$ have their centres separated by a distance of $50 \;cm$. What is the mutual force of electrostatic repulsion if the charge on each is $6.5 \times 10^{-7}\; C?$ The radii of $A$ and $B$ are negligible compared to the distance of separation.
$(b)$ What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved?
Three charges each of magnitude $q$ are placed at the corners of an equilateral triangle, the electrostatic force on the charge placed at the center is (each side of triangle is $L$)
A charge $+q$ is situated at a distance $d$ away from both the sides of a grounded conducting $L$ shaped sheet as shown in the figure.The force acting on the charge $+q$ is
Two point charges $3 \times 10^{-6} \,C$ and $8 \times 10^{-6} \, C$ repel each other by a force of $6 \times 10^{-3} \, N$. If each of them is given an additional charge $-6 \times 10^{-6} \, C$, the force between them will be
When ${10^{14}}$ electrons are removed from a neutral metal sphere, the charge on the sphere becomes......$\mu C$