A capacitor connected to a 10 V battery collects a charge of 40 μC with air as dielectric, and 100 μC with oil as dielectric. The dielectric constant of oil is
Two equally charged small balls A and B, placed at a fixed distance experience a force F. A smilar uncharged ball C after touching one of them is placed at a middle point between the two balls. The force experienced by ball A, is
2F
4F
A capacitor of capacitance 2 μF is charged to a potential difference of 200 volts. After disconnecting from the battery, it is connected in parallel with another uncharged capacitor. The common potential is 40 volts. The capacitance of the second capacitor is
Two spheres of radii r1 and r2 are charged to the same potential. If s1 and s2 are surface densities of charges on the two, then ratio is
