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 concentric spheres of radii R and r have similar charges with equal surface densities (σ). What is the electric potential at their common centre?
none of these
A particle of mass m and charge q is placed at rest in a uniform electric field E and then released. The Kinetic energy attained by the particle after moving a distance y is
q E y2
q E2 y
q E y
q2 E y
A charge q is placed at the centre of the line joining two exactly equal positive charges Q. The system of three charges will be in equilibrium, if q is equal to
- Q/4
+ Q
- Q
Q/2
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
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 100 μF capacitor is charged to a potential difference of 50 V, the charging battery then being disconnected. The capacitor is then connected to a second capacitor. If the measured potential difference drops to 35 V, the capacitance of the second capacitor is
52 μF
37 μF
59 μF
43 μF
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
