Electrostatic Potential and Capacitance

The difference in the capacitance (in F) between the metal plates at t=0 and that at t=500 s is (8-n) 0, where 0 is the permittivity of free space. The value of n is:

An infinitely long thin wire, having a uniform charge density per unit length of 5 nC/m, is passing through a spherical shell of radius 1 m, as shown in the figure. A 10 nC charge is distributed uniformly over the spherical shell. If the configuration of the charges remains static, the magnitude of the potential difference between points P and R, in Volt, is . [Given: In SI units 14 0 = 9 109, 2 = 0.7. Ignore the area pierced by the wire.] [figure]