Electric Charge

Electric charge is a fundamental property of matter responsible for electrical interactions.

The SI unit of charge is coulomb (C).

There are two types of charges.

1. Positive charge

2. Negative charge

Like charges repel each other while unlike charges attract each other.

Charge is represented by the symbol q.

Properties of Electric Charge

Electric charge possesses three important properties: additivity, conservation, and quantization.

Additivity of Charge

The total charge on a system is equal to the algebraic sum of all individual charges present in the system.

Positive and negative signs must be considered while adding charges.

For example, if a body contains +5 C and −2 C charges, the net charge becomes +3 C.

Conservation of Charge

Charge can neither be created nor destroyed.

It can only be transferred from one body to another.

The total charge of an isolated system always remains constant.

If one body loses electrons, another body gains the same number of electrons.

Quantization of Charge

Charge exists in discrete packets and not in arbitrary amounts.

The smallest charge that can exist independently is called the elementary charge.

The charge on any body is always an integral multiple of the elementary charge.

where

If a body gains electrons, n becomes negative.

If a body loses electrons, n becomes positive.

Charging of Bodies

A neutral body can be charged by transferring electrons from one body to another.

Charging mainly takes place due to transfer of electrons.

Protons remain fixed inside the nucleus and usually do not move from one body to another.

If a body gains electrons, it becomes negatively charged.

If a body loses electrons, it becomes positively charged.

Charging by Friction

When two suitable materials are rubbed together, electrons transfer from one material to another.

One body becomes positively charged while the other becomes negatively charged.

Example: Rubbing a glass rod with silk.

In this case, electrons are transferred from glass to silk.

Glass rod becomes positively charged and silk becomes negatively charged.

Charging by Conduction

When a charged conductor touches a neutral conductor, charges flow between them.

The neutral conductor acquires the same type of charge as the charged conductor.

This method requires direct physical contact between the bodies.

Charging by Induction

In induction, a conductor is charged without direct contact.

A nearby charged object causes redistribution of charges within the conductor.

When proper grounding is done, some charges flow to or from the earth.

After removing the ground connection and then the inducing charge, the conductor remains charged.

The charge acquired by the conductor is opposite to the inducing charge.