2nd Year Physics Chapter 12 Electrostatistics Notes

Chapter 12 Electrostatistics

MCQ

1. If the medium between the charges is not free space then electrostatic force will:

(a)  Increase   (b)  Decrease   (c)  Remain same   (d)  None of these

2. SI unit of permittivity of free space are:

(a)  Nm²C^-2   (b)  N^-1m^-2C^-1   (c)  N^-1m^-1C²   (d)  N^-1m^-2C²

3. Numerical value of permittivity of free space is:

(a)  9×10⁹ Nm²C^-2  (b)  8.85×10^-12 Nm²C^-2  (c)  8.85×10^-12 N^-1m^-2C²  (d) Both b and c 

4. Two charges 1pC and 5pC separated by 20cm, the ratio of electrical forces acting on them will be:

(a)  1:2   (b)  1:5   (c)  1:1   (d)  5:1

5. The concept of an electric field lines is introduced by:

(a)  Coulomb   (b)  Faraday   (c)  Einstein   (d)  Joseph Henry

6. One Joule is equal to:

(a)  1.6×10^-19 eV   (b)  1.6×10¹⁹ eV   (c)  6.25×10^-18 eV   (d)  6.25×10¹⁸ eV

7. Photocopier and inkjet printer are the applications of:

(a)  Magnetism   (b)  Electricity   (c)  Electro-magnetism   (d)  Electrostatic

8. Selenium is a:

(a)  Insulator in light   (b)  Insulator in dark  (c)  Conductor in dark  (d)  Semiconductor in dark

9. Which one of the following can be taken as measure of electric field intensity:

(a)      (b)  )      (c)  )       (d) 

10. Two opposite point charge of same magnitude separated by distance 2d, electric potential midway between them is:

(a)  1 V   (b)  2 V   (c)  Zero   (d)  V/2

11. If charged body is moved against the electric field, it will gain:

(a)  P.E    (b)  K.E   (c)  Mechanical energy   (d)  Electric potential energy

12. The quantity time constant RC has units of:

(a)  Charge   (b)  Time   (c)  Capacitance   (d)  Resistance

13. S.I unit of strength of electric field is:

(a)  J/C   (b)  C/V   (c)  N/C   (d)  J/N

14. If the distance between the two charged bodies is halved, the force between them becomes:

(a)  Double   (b)  Half   (c)  Four times   (d)  One fourth

15. Coulomb/Volt is called:

(a)  Farad   (b)  Ampere   (c)  Joule   (d)  Henry

Short Questions

1. Define dielectric constant for capacitors. Also write its unit.

Ans. It is defined as “the ratio of the capacitance of a parallel plate capacitor with an insulating substance as the medium between the plates to its capacitance with a vacuum (or air) as a medium between them.”

Mathematically, dielectric constant can be written as

                                                                   ɛ_r = C_med / C_vac 

2. Describe any two difference between gravitational and electrical forces.

Ans. (a) Gravitational Force:

1.                 It is a long-range force.
2.                It is a very weak force as compared to always attractive electrical force at the same distance.
3.          Mathematically, it is written as F_g = 10^-38 F_e.
4.                It does not depend upon the medium.

(b) Electrical Force:

1.                    It is short-range force and it may be attractive or repulsive.
2.                   It depends upon the medium.
3.                   It is a very strong force as compared to gravitational force.