# Electric Charge | SI Unit of Charge | Properties of Charge

Contents

## What is Electric Charge

It is the basic property of matter carried by elementary particles that causes it to experience a force when placed in magnetic or electric field. It is denoted by āqā and its SI unit is coulomb , denoted by āCā.

The elementary particles of matter are atoms. The atoms are made of electrons, protons and neutrons.

There are two types of electric charges: positive charge and negative charge. The protons carry positive charge, electrons carry negative charge and neutrons are neutral i.e. they do not carry any charge. The charge of a proton is equal to and opposite to that of an electron. The charge of proton is 1.602 \times 10^{-19}C while as the charge of electron is -1.602 \times 10^{-19}C.

Total charge of an atom can be calculate by \\\;\\q=n_{1}P+n_{2}e\\ Where q is total charge of atom, “n1” is number of protons, “P” is charge of proton, “e” is charge of electron, “n2” number of electrons. one coulomb of charge is equal to 6.242 x 1018 electrons.

A negatively charged object has an excess of electrons on its surface. similarly, a positively charged object has excess of protons on its surface.

Static charges produce Electric Field and when these charges start to move and become dynamic, they produce a magnetic field. Like charges repel each other and Unlike charges attract each other.

## How we Observe or perceive Charge

To perceive or observe charge we will perform a simple experiment. Take a comb and some strips of paper. \\1. Take the comb close the strips of paper as shown in figure (1) nothing will happen. \\2. Comb your dry hair as shown in figure (2). \\3. Put the comb close to the strips of paper, the strips of paper are attracted towards the comb and even cling to it as shown in figure (3). This is due the charge obtained by a comb when you rubbed it with your dry hair.

## Properties of Charge

Various properties of charge include the following:

2. Conservation of Electric Charge
3. Quantization of Electric Charge

Additive of Electric Charge:- The additive property of electric charges says that if there are “n” number of charges present inside an isolated system, The total charge of the system will be the algebraic sum of the individual charges. Let us consider a system, containing three point charges with magnitudes q1, q2, and q3. In such a system, the total charge (Q) of the system can be obtained by algebraically adding the three charges.\\Q = q1 + q2 + q3 .\\ Similarly system containing “n” charges, total charge (Q) of the system will be \\ Q = q1 + q2 + q3 +……+qn.

Conservation of Electric Charge:- The Conservation of charges says that the charges are neither created not destroyed. They can be transferred from one body to another, but they cannot be created or destroyed. In an Isolated system, the charges are always conserved.

Consider two bodies “A” and “B” as shown in figure below. Initially the bodies are separated from each other, body “A” have 10C of charge and body “B” are neutral. Total charge of the system is 10C. When two bodies are connected to each other, 5C of charge gets transferred from body “A” to body “B”. Total charge of the system are still 10C i.e. charge is neither created nor destroyed.

Quantization of Electric Charge:- Charge quantization is the principle that the charge of any object is an integer multiple of the elementary charge (i.e. electron (e)). Thus, an object’s charge can be exactly 0 e, or exactly 1 e, ā1 e, 2 e, etc., but not, say, 0.5e, or ā3.8 e, hence, in any system, The charges will be \\q = ne where n = …..-4, -3, -2, -1, 0, 1, 2, 3……