Electric Charge...

A point charge $q$ is revolving in a circle of radius $' r '$ around a fixed infinite line charge with positive charge $\lambda$ per unit length. Now the point charge is shifted and it revolves in a circle of radius $2 r$. Then :

Two similar very small conducting spheres having charges $40  C$ and $-20  C$ are at some distance apart. Now they are touched and then kept at a same initial distance. The ratio of the initial to the final force between them is:

A long cylindrical wire carries a linear charge density of $3\times 10^{-8} Cm^{-1}$. An electron revolve around it in a circular path under the influence of the attractive force. $KE$ of the electron is :

A dipole is placed in a shell as shown. Find the electric flux emerging out of the shell and in a hypothetical sphere of radius r as shown.

The charge per unit length for a very long straight wire is $\lambda$. The electric field at points near the wire (but outside it) and far from the ends varies with distance r as :

Suppose that $$1.0\  g$$ of hydrogen is separated into electrons and protons. Suppose also that the protons are placed at the earth's north pole and the electrons are placed at the south pole. What is the resulting compression force on earth? (Given that the radius of earth is $$6400\  km$$)

In the figure shown, A is a fixed charge. Another charge B (of mass m) is given a velocity v perpendicular to line AB. At this moment the radius of curvature of the resultant path of B is-

A hemisphere of radius r is placed in a uniform electric field of strength E. The electric flux through the hemisphere is :

Two identical small conducting spheres, having charges of opposite sign, attract each other with a force of $0.108N$ when separated by $0.5m$. The spheres are connected by a conducting wire, which is then removed, and thereafter, they repel each other with a force of $0.036N$. The initial charges of the spheres are :

Two small spheres each of radius 1 mm are kept 10 cm apart. Assuming each proton has a charge +e and each electron has a charge 0.1% less than +e then find the force between the two spheres. Density of copper is 8.9 gcm$^{-3}$ and atomic mass number is 63.5.