Electrostatic Potential and Capacitance · Question 25

Two charged spherical conductors of radius R1 and R2 are connected by a wire. Then the ratio of surface charge densities of the spheres ( 1 / 2) is :

1. R12R22
2. R1R2
3. R2R1
4. ( R1R2 )

The equivalent capacitance of the combination shown in the figure is : [figure]

1. 3C/2
2. 3C
3. 2C
4. C/2

Twenty seven drops of same size are charged at 220 V each. They combine to form a bigger drop. Calculate the potential of the bigger drop.

1. 1980 V
2. 660 V
3. 1320 V
4. 1520 V

A short electric dipole has a dipole moment of 16 10-9 C m. The electric potential due to the dipole at a point at a distance of 0.6 m from the centre of the dipole, situated on a line making an angle of 60 with the dipole axis is : ( 14 0 = 9 109 N m2/C2 )

1. 200 V
2. 400 V
3. zero
4. 50 V

The capacitance of a parallel plate capacitor with air as medium is 6 . With the introduction of a dielectric medium, the capacitance becomes 30 . The permittivity of the medium is : ( 0 = 8.85 10-12 C2 N-1 m-2)

1. 1.77 10-12 C2 N-1 m-2
2. 0.44 10-10 C2 N-1 m-2
3. 5.00 C2 N-1 m-2
4. 0.44 10-13 C2 N-1 m-2

In a certain region of space with volume 0.2 m3, the electric potential is found to be 5 V throughout. The magnitude of electric field in this region is :

1. 0.5 N/C
2. 1 N/C
3. 5 N/C
4. zero

The electrostatic force between the metal plates of an isolated parallel plate capacitor C having a charge Q and area A, is

1. Independent of the distance between the plates
2. Linearly proportional to the distance between the plates
3. Proportional to the square root of the distance between the plates
4. Inversely proportional to the distance between the plates

A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system

1. decreases by a factor of 2
2. remains the same
3. increases by a factor of 2
4. increases by a factor of 4

The diagrams below show regions of equipotentials. [figure] A positive charge is moved from A to B in each diagram.

1. In all the four cases the work done is the same.
2. Minimum work is required to move q in figure (I).
3. Maximum work is required to move q in figure (II).
4. Maximum work is required to move q in figure (III)

A capacitor of 2 is charged as shown in the diagram. When the switch S is turned to position 2, the percentage of its stored energy dissipated is [figure]

1. 75%
2. 80%
3. 0%
4. 20%