Electrostatic Potential and Capacitance · Question 22

Six charges +q, -q, +q, -q, +q, and -q are fixed at the corners of a hexagon of side d as shown in the figure. The work done in bringing a charge q0 to the centre of the hexagon from infinity is ( 0 - permittivity of free space) [figure]

1. -q24 0 d (6 - 1 2 )
2. Zero
3. -q24 0 d
4. -q24 0 d (3 - 1 2 )

A parallel plate capacitor has a uniform electric field E in the space between the plates. If the distance between the plates is 'd' and the area of each plate is 'A', the energy stored in the capacitor is : ( 0 = permittivity of free space)

1. E2Ad 0
2. 12 0E2
3. 0EAd
4. 12 0E2Ad

Polar molecules are the molecules :

1. having a permanent electric dipole moment
2. having zero dipole moment
3. acquire a dipole moment only in the presence of electric field due to displacement of charges
4. acquire a dipole moment only when magnetic field is absent

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