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
The dielectric strength of air at NTP is 3 x 106 V/m. The maximum charge that can be given to a spherical conductor of radius 3 m is
3 x 104 C
3 x 10-3 C
3 x 10-2 C
3 x 10-1 C
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 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
An electric dipole, consisting of two opposite charges of 2 x 10-6 C each separated by a distance 3 cm is placed in an elecric field of 2 x 105N/C. Torque on the dipole is
12 x 10-1 Nm
12 x 10-2 Nm
12 x 10-3 Nm
12 x 10-4 Nm
The electric potential V at any point (x1, y1, z1) in space is given by V = 4x2 volt. The electric field at (1, 0, 2) m in Vm-1 is
8, along negative x-axis
8, along positive x-axis
16, along negative x-axis
16, along positive y-axis
A 4 μF conductor is charged to 400 V and then its plates are joined through a resistance of 1 kΩ. The heat produced in the resistance is
0.16 J
1.28 J
0.64 J
0.32 J
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
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
A pendulum bob of mass 30.7 x 10-6 kg and carrying a charge 2 x 10-8 C is at rest in a horizontal uniform electric field of 20000 V/m. The tension in the thread of the pendulum is (g = 9.8 m/s2).
3 x 104 N
4 x 10-4 N
5 x 10-4 N
6 x 10-4 N
