Electric Charges and Fields

The electric field is $$100 V/m$$, at a distance of $$20\ cm$$ from the center of a dielectric sphere of radius $$10\ cm$$. Then E  at $$3\ cm$$ distance from the center of the sphere is :

A sphere carrying a charge of $$0.01\  C$$ is kept at rest without falling down, touching a wall by applying an electric field $$100 \ N/C$$. If the coefficient of friction between the sphere and the wall is $$0.2$$, the weight of the sphere is:

Three charges of respective values $$- \sqrt{2} \mu C, 2\sqrt{2} \mu C $$ and $$-\sqrt{2} \mu C$$ are arranged along a straight line as shown in the figure. Calculate the total electric field intensity due to all three charges at the point P.
A positive point charge Q is kept (as shown in the fig.) inside a neutral conducting shell whose centre is at C. An external uniform electric field E is applied. Then