Electric Charge...

A hollow metal sphere of radius R is uniformly charged. The electric field due to the sphere at a distance r from the centre 

Electric field outside a long wire carrying charge q is proportional to :

An electric line of force in the $$xy-plane$$ is given by equation $$x^{2} + y^{2} = 1$$. A particle with unit positive charge, initially at rest at the point $$x = 1, y = 0$$ in the $$xy - plane$$.

Two identical charged spheres suspended from a common distance $$d(d < < 1)$$ apart because of their mutual repulsion. The charged begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity $$v$$. Then $$v$$ varies as a function of the distance $$x$$ between the spheres, as

Two unlike charges attract each other with a force of 10N. If the distance between them is doubled, the force between them is :

Number of electric lines of force emanating from $$1C$$ of positive charge in vacuum is :

A force ‘F’ is acting between two charges in air. If the space between them be completely filled with a medium $$K=4$$, the force will be :

An electron revolves around the nucleus of hydrogen atom in a circle of radius $$5\times 10^{-11}\ m$$. The intensity of electric field at a point in the orbit of the electron is:

A charge $$q_1$$ exerts a force of $$45N$$ on a charge of $$q_{2}=10^{-5} C$$ located at a point $$0.2m$$ from $$q_{1}$$. The magnitude of $$q_{1}$$ is

When we remove polyester or woollen clothes in dark, we can see a spark and hear a crackling sound. Which of the following is responsible for it?