## Electric Charge and its properties

What is Electric Charge?
Electric charge is an intrinsic property of elementary particles, like electron, proton and neutron etc., of any substance which gives rise to electric force between these elementary particles.

Types of Charge:

There are two types of electric charge
1. Positive Electric Charge like Proton
2. Negative Electric Charge like Electron

The same nature of charged particles repels each other and opposite nature of charged particles attract each other. For example electron and electron repel each other and electron and proton attract each other. Similarly proton and proton repel each other.
 Electric force between charged particles
Generally, any substance is electrically neutral because the number of electrons and protons are equal in it but according to Free electron Model theory these substances are classified into three categories. These are:

1. Conductor
2. Semiconductor
3. Insulator

The electric force is generated in conductors and insulating substances but not in semiconductor substances because these semiconductor substances have four electrons in its valence shell.

Generation of Electric force in Conductor:

The electric force is generated in conductors due to the transfer of electrons from one conducting substance to other conducting substance. There are various methods for the transfer of electrons in conductors, like contact, friction, and induction. Therefore, When electrons is transfer from one conductor to another conductor then conductor have deficiency or excess of electrons , these conductors are called Electrostatically charged. There are two types of electrostatic charged conductors.

1.) Positive Electrostatic Charged Conductor:

When conductors have deficiency of electrons i.e number of electrons are less than proton, these conductors are called positive electrostatic charged conductors.

2.) Negative Electrostatic Charged Conductor:

When conductors have excessive electrons i.e number of electrons are greater than protons, these conductors are called negative electrostatic charged conductors.

Generation of Electric force in Insulator:

Insulators are charged by induction this charging occurs due to polarization of atoms of insulating substances.In the absence of an external electric field, the center of mass of nucleus and electron cloud in an atom lies on same point but when insulating substance is placed in an external electric field, the center of mass of nucleus and electron cloud in atom is separated from each other at a very small distance. The center of mass of electron cloud is shifted towards the positive side of external electric field and the center of mass of nucleus is shifted toward the negative side of the external electric field. thus these atom are polarize.When insulators are electrically charged, these polarized atoms store the electric potential energy.

Basic Properties of Electric Charge:

• Additive Nature of Charge:

If a system contains $'n'$ number of point charges, the total charge of a system will be sum of $'n'$ number of point charges.
 Additive nature of charge
Let us consider, a system containing $'n'$ number of point charges like $q_{1},q_{2},q_{3}......q_{n}$, the total charge of the system will be

$Q=q_{1}+q_{2}+q_{3},.....+q_{n}$

 $Q=\sum_{i}^{n}q_{i}$

• Conservation of Charge:

The total Charge of the isolated system is always conserved i.e “ Electric charge neither can be create nor destroy”.
 Conservation of charge

• Quantization of Charge:

The electric charge is always an integer multiple of $‘e’$. It is known as quantization of charge.

 $Q=\pm ne$

Where $'n'$ is integer number.

• Mass of charge particle depends on velocity:

The velocity of charge particle is significant to speed of light so mass of the charge particle depends on the velocity. This variation can be find by following formula:

 $m=\frac{m_{0}}{\sqrt{1-\frac{v^{2}}{c^{2}}}}$

Where
$m_{0}$ - Rest mass of particle
$m$ - Relative mass of particle