NCERT Class 10 The most Important Basic concepts of chapter 12 (Electricity) part 1

The most Important points of Electricity (part-1).

1. Frictional electricity: The property due to which rubbed substances attract light objects is called electricity. The electricity developed by rubbing or friction is called frictional electricity. 

2. Positive and negative charges: The charge acquired by a glass rod when rubbed with silk is called positive charge and the charge acquired by an ebonite rod when rubbed with silk is called positive charge and the charge acquired by an ebonite rod when rubbed with wool is called negative charge.

3. Fundamental law of electrostatics: Like charges repel and unlike charges attract each other.

4. Coulomb's law: The force of attraction or repulsion between two point charges is 

(i) Directly proportional to the product (q1q2) of the two charges and

(ii) Inversely proportional to the square of the distance (r) between them.

Mathematically, 

            F = K q1q2 / r²

The value of K depends on the nature of the medium between the two charges and the system of units chosen.

For charges in vacuum, 

          K = 9 × 10⁹ Nm²/C².

5. Coulomb: It is the SI unit of charges. One coloumb is defined as that amount of charge which repels an equal and similar charge with a force of  9 × 10⁹ N  when placed in vacuum at a distance of 1 metre from it.

Charge on an electron = -1.6 × 10-⁹ coulomb.

6. Law of Conservation of charge: Electric charges can neither be created nor destroyed, they can only be transferred from one body to another.

7. Static and current electricities: Static electricity deals with the electric charges at rest while the current electricity deals with the electric charges in motion.

8. Conductor: A substance which allows passage of electric charges through it easily, is called a 'conductor'. A conductor offers very low resistance to the flow of current.

For example, copper, silver, aluminium, etc.

9. Insulator: A substance that has infinitely high resistance does not allow electric current to flow through it. It is called an 'insulator'. For example, rubber, plastic, glass, ebonite, etc.

10. Electric current: The electric current is defined as the rate of flow of Electric charge through any section of a conductor. 

 Electric current = charge / time

                           I  =  Q / t 

Electric current is a scalar quantity.

11. Ampere: It is the SI unit of current. If one coulumb of charge flows through any section of a conductor in one second, then current through it is said to be one ampere.

12. Electric circuit: The closed path along which an electric current flows is called an Electric circuit.

13. Conventional current: Conventionally, the direction of motion of positive charges is taken as the direction of current. The direction of conventional current is opposite to that of the negatively charged electrons.

14. Electric field: It is the region around a charged body within which it's influence can be experienced.

15. Electrostatic potential: Electrostatic potential at any point in an electric field is defined as the amount of work done in bringing a unit positive charge from infinity to that point. It's unit is volt.

16. One volt potential: The electrostatic potential at a point in an electric field is said to be one volt if one joule of work has to be done in bringing a positive charge of one coulomb from infinity to that point.

17. Potential difference between two points: The potential difference between two points in an electric field is the amount of work done in bringing a unit positive charge from one point to another.

 Potential difference = work done / charge

                                  V = W / Q

18. One volt potential difference: The potential difference between two points in an electric field is said to be one volt if one joule of work has to be done in bringing a positive charge of one coulomb from one point to another.

             1 volt = 1 joule / 1 coulomb

                  1V = 1J / 1C

19. Electrochemical or voltaic cell: It is a device which converts Chemical energy into electrical energy.

20. Galvanometer : It is a device to detect current in an electric circuit.

21. Ammeter: It is a device to measure current in a circuit. It is a low resistance galvanometer and is always connected in series in a circuit.

22. Voltmeter: It is a device to measure potential difference. It is a high resistance galvanometer and is always connected in parallel to the component across which the potential difference is to be measured.