Electric Charge...

The field at a distance $$r$$ from a long straight wire of charge per unit length $$\lambda$$ is:

The solid angle subtended by the periphery of an area $$1 cm^2$$ at a point situated symmetrically at a distance of 5 cm from the area is

The forces between two small charged spheres having charges of $$1\times { 10 }^{ -7 }C$$ and $$2\times { 10 }^{ -7 }C$$ placed $$20cm$$ apart in air is:

Two point charges exert on each other a force $$F$$ when they are placed $$r$$ distant apart in air. When they are placed $$R$$ distance apart in a medium of dielectric constant K, they were exerting the same force. The distance $$R$$ equals

The constant $$k$$ in Coulomb's law depends upon

The electrostatic attracting force on a small sphere of charge $$0.2\mu C$$ due to another small sphere of charge $$-0.4\mu C$$ in air is $$0.4N$$. The distance between the two spheres is

A change of $$1\ \mu C$$ is divided into two parts such that their charges are in the ratio of 2:3. These two charges are kept at a distance 1 m apart in vaccum. Then, the electric force between them (in Newton) is

Two insulated charged metallic spheres $$P$$ and $$Q$$ have their centres separated by a distance of $$60cm$$. The radii of $$P$$ and $$Q$$ are negligible compared to the distance of separation. The mutual force of electrostatic repulsion if the charge on each is $$3.2\times { 10 }^{ -7 }C$$ is:

The acceleration for electron and proton due to electrical force of their mutual attraction when they are $$1\mathring {A}$$ apart is

A charge $$Q$$ is placed at the centre of the line joining two point charges $$+q$$ and $$+q$$ as shown in figure, The system is in equilibrium. The ratio of charges $$Q$$ and $$q$$ is