1. A parallel-plate capacitor with air between the plates has a capacitance of 10 pF. If the distance between the parallel plates is halved and the space between the plates is filled with a material of dielectric constant 5, the newly formed capacitor will have a capacitance of

- 50 pF
- 10 pF
- 150 pF
- 100 pF

2. The maximum potential-gradient that can be imposed in air at atmospheric pressure without breakdown is 30 kV/cm. The corresponding energy density is nearly

- 30 J/m
^{3} - 35 J/m
^{3} - 40 J/m
^{3} - 45 J/m
^{3}

3. If a positively charged body is placed inside a spherical hollow conductor, what will be the polarity of charge inside and outside the hollow conductor?

- Inside positive, outside negative
- Inside negative, outside positive
- Both negative
- Both positive

4. “Electrical flux enclosed by a surface surrounding a charge is equal to the amount of charge enclosed.” This is the statement of

- Faraday’s law
- Lenz’s law
- Modified Ampere’s law
- Gauss’s law

5. Gauss’s theorem states that total electric flux emanating from a closed surface is equal to

- total current density on the surface
- total charge enclosed by that surface
- total current on the surface
- total charge density within the surface

6. The dielectric strength of rubber is 40000 V/mm at frequency of 50 Hz. What is the thickness of insulation required on an electrical conductor at 33 kV to sustain the breakdown?

- 0.83 mm
- 8.3 mm
- 8.3 cm
- 0.083 mm

7. Consider the following types of transmission lines:

- Open-wire line
- Twin-lead wire
- Coaxial cable

The capacitance per metre will be least in which of the above transmission lines?

- ii only
- i only
- i, ii and iii
- iii only

8. The capacitance of a conducting sphere of radius r with a total charge of q uniformly distributed on its surface is

- proportional to qr
- independent of r
- proportional to $\frac{q}{r}$
- independent of q

9. The field strength at a point of finite distance from an infinitely long straight uniformly charged conductor is obtained by considering the radial (R) component and the longitudinal (L) component of the forces acting on a unit charge at the point, by the charges on the elemental length of the conductor. The resultant field strength is

- the sum of R-components, when the sum of L-components is zero
- the sum of L-components, when the sum of R-components is zero
- the sum of both R- and L-components
- average of the sums of R- and L- components

10. In practice, Earth is chosen as a place of zero electric potential because it

- is non-conducting
- is easily available reference
- keeps losing and gaining electric charge every day
- has almost constant potential

11. Consider the following statements associated with the basic electrostatic properties of ideal conductors:

- The resultant field inside is zero.
- The net charge density in the interior is zero.
- Any net charges reside on the surface
- The surface is always equipotential.
- The field just outside is zero.

Which of the above statements are correct?

- i, ii, iii and iv
- iii, iv and v only
- i, ii and iii only
- ii and iii only

12. The electric field lines and equipotential lines

- are parallel to each other
- are one and the same
- cut each other orthogonally
- can be inclined to each other at any angle

13. The electrostatic force of repulsion between two α-particles of charges 4.0 x 10^{-19} C each, and separated by a distance of 10^{-10} cm is

(Given ε_{o} = 8.854 x 10^{-12} Nm^{2}/C^{2})

- 57.6 x 10
^{-4}N - 28.8 x 10
^{-4}N - 14.4 x 10
^{-4}N - 3.6 x 10
^{-4}N

14. If E = 0 at all points on a closed surface

- The electric flux through the surface is zero.
- The total charge enclosed by the surface is zero.
- Charge resides on the surface.

- i and ii only
- i and iii only
- ii and iii only
- i, ii and iii

15. Two identical coaxial circular loops carry the same current circulating in the same direction. If the loops approached each other, then the current in

- each one of them will increase
- both of them will remain the same
- each one of them will decrease
- one will increase while in the other the current will decrease

16. A quantitative relation between induced emf and rate of change of flux linkage is known as

- Maxwell’s law
- Stoke’s law
- Lenz’s law
- Faraday’s law

17. The equation of continuity defines the relation between

- electric field and magnetic field
- electric field and charge density
- flux density and charge density
- current density and charge density

18. Electric flux through a surface area is the integral of the

- normal component of the electric field over the area.
- parallel component of the electric field over the area.
- normal component of the magnetic field over the area.
- parallel component of the magnetic field over the area.

19. The following point charges are located in air:

+0.008 μC at (0, 0) m

+0.05 μC at (3, 0) mn

-0.009 μC at (0, 4) m

The total electric flux over a sphere of 5 m radius with centre (0, 0) is

- 0.058 μC
- 0.049 μC
- 0.029 μC
- 0.016 μC

20. Two charges are placed at a distance apart. Now, if a glass slab is inserted between them, then the force between the charges will

- reduce to zero
- increase
- decrease
- not change