Electric Charge and Its Nature

Introduction:

Human beings have known about electricity and its effects for thousands of years. Repulsive and attractive properties of electricity were known to the Greek since 600 BC. It is quite a common experience that when we rub our dry hair with a dry comb for a couple of minutes then we observe that the comb starts attracting pieces of paper. All these natural phenomena are related to electricity and current.

Electric charge:

Charge is defined as the property of a material due to which it shows electrical and magnetic effects. In the atomic scale, every atom consists of electrons, which are the negatively charged particles, and protons, which are positively charged particles. 

Properties of charge:

1. Charge can be transferred from one material to another; so, an uncharged body can be charged with the help of another charged body.
2. Charge is always associated with some mass i.e it cannot exist independently.
3. Charge is a conserved physical quantity just like momentum, mass, energy, etc in physics.
4. The magnitude of the charge is always an integral multiple of 1.6*10-19C i.e charge is quantized.

This is the charge that an electron contains. Hence we can say that this is the lowest possible charge that exists in nature.

Illustration: Suppose a material has a charge of 19.2*10-16C. How many electrons does it contain?

=Since 19.2*10-16C  is the charge of one electron hence the number of electrons contained in the material is:19.2*10-16 /1.6*10-19=12000 electrons.

5. Charges add additives. Example: 5 C and 3 C of charge will together give 8 C of charge.
6. Invariance of charge: The numerical value of the charge of any particle is independent of other physical quantities like its velocity speed acceleration. 

Example: The electrons move with a very high velocity around the nucleus in an atom whereas the protons remain on the nucleus with only slight vibrations. Yet the charge on both the subatomic particle remains constant i.e 1.6*10-19C.

Charge can produce both electric and magnetic fields. While the static charge produces an electric field, an accelerated charge can produce both electric and magnetic fields. 

Conductors:

Materials that can conduct electricity are known as conductors: for example, iron, aluminium, copper etc. In the case of the conductors, the valence electrons on the atoms are loosely bounded. Hence the electrons can easily get transferred from one atom to another.

Insulators: Materials that cannot conduct electricity are known as insulators: for example, wood plastics etc. In such materials, the electrons are not loosely bonded in the atoms.

Methods of charging:

There are many methods to induce charge in a material:

1. Charging by friction:

When two objects are rubbed together then the transfer of electrons takes place from one body to another. There is a difference in the magnitude of charges between the two bodies; hence, charging takes place in both the materials.

Example: A glass rod is rubbed with a cloth and becomes electrically charged.

2. Charging by conduction:

Charging by conduction needs physical contact between two materials. Both the materials should be conductors; one among them should be charged and another uncharged. Printed material is in contact with the uncharged material then the charge of the charged particles spreads out under the repulsion to both the charged and uncharged body. Thus, charging takes place.

3. Charging by induction:

This is a method of inducing charges in another body by a charged body without losing its own charge or any physical contact with the uncharged body.

The process takes place as follows:

1. First a charged body is brought near the uncharged body.
2. The charged body attracts the opposite charge and repels a similar charge. Hence redistribution of charge takes place in the neutral body. Now whenever earthing is done, i.e contacting a wire dug into the earth with the neutral body, only one charge is left.

Hence charge is induced in the body.

Conclusion:

Electric charge is a fundamental property of matter. This is a conservative physical quantity and does not exist only with mass. Electric charge is the property of any matter for which it shows magnetic and electric effects or phenomena. Charges can be transferred from one body to another through the process of rubbing induction etc. It is quantized and hence always an integral multiple of the charge of electrons, which is 1.6*10 -19 coulomb. Conductors are those substances that can conduct electricity. Charging of a body can be done by rubbing two bodies, induction, conduction, etc. Charging by friction and charging by conduction requires physical contact between the two materials whereas the charging by induction process does not need any physical contact between the two materials.