The work done in carrying a charge Q once round the circle of radius r with charge Q at the centre of the circle is
zero
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
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
2 μF
4 μF
8 μF
16 μF
The formation of a dipole is due to two equal and dissimilar point charges placed at a
short distance
long distance
above each other
none of the above
The potential of a point A is -500 V and that of another point B is +500 V. The work done by an external agent to take 2 units of negative charge from B to A is
+1000 J
-1000 J
+2000 J
-2000 J
A cylinder of radius R and length L is placed in a uniform electric field E parallel to the axis of the cylinder. The total flux from the surface of cylinder is given by
2pR2E
Zero
The dielectric strength of air at NTP is 3 × 106 V/m. The maximum charge that can be given to a spherical conductor of radius 3 m is
3 × 104 C
3 × 10-3 C
3 × 10-2 C
3 × 10-1 C
Two equally charged small balls A and B, placed at a fixed distance experience a force F. A similar 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
Two identical metal balls with charges +2Q and -Q are separated by some distance, and exert a force F on each other. They are joined by a conducting wire, which is then removed. The force between them will now be
F
F/2
F/4
F/8
Electric potential of earth is taken to be zero because earth is a good
dielectric
semiconductor
insulator
conductor