The electric field required to just support a water droplet of mass 10-5 g, which has a charge of 10-13 C is
107 V m-1
9.8 × 103 V m-1
106 V m-1
9.8 × 105 V m-1
On moving a charge of 20 coulomb by 2cm, 2 J of work is done, then the potential difference between the points is
0.1 V
8 V
2 V
0.5 V
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
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
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
Capacitance (in F) of a spherical conductor with radius 1 m is
1.1 × 10-10
10-6
9 × 10-6
10-3
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
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
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
4
8
2.5
1.5
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
