Consider a region inside which, there are various types of charges but the total charge is zero. At points outside the region

the dominant electric field is inversely pro-portional to r3, for large r (distance from origin).

the electric field is necessarily zero.

the work done to move a charged particle along a closed path, away from the region will not be zero.

the electric field is due to the dipole moment of the charge distribution only.

A force F acts between two charges +Q and -Q that is placed at a certain distance from each other. The third sphere of charge Q is placed between them. What is the magnitude and force experienced by the third charge?

8F in the direction of -Q charge

3F in the direction of +Q charge

4F in the direction of +Q charge

Electric Charge and Electrification

An Electric Charge is a fundamental property of matter and never found free. There are two kinds of electric charges, namely positive and negative charges. If a body has an excess of electrons, it is said to be negatively charged, and if it is deficient in electrons, it is said to be positively charged.

Introduction to Electric Charge

Benjamin Franklin introduced the concept of positive and negative charges.
Repulsion is the sure test for the detection of a charge.
In the SI system, the unit of charge is the coulomb.
Electric charge is a scalar quantity.
Like charges repel and unlike charges attract.
Electric charge is conserved. It can neither be created nor destroyed. It can only be transferred from one object to another.
The charge is quantised. The smallest charge is associated with an electron (-), and proton (+) is 1.610^–19 coulomb.
All charges in nature exist as integral multiples of electron charge, i.e., q = n.e.
A coulomb is equivalent to a charge of 6.24310¹⁸ electrons.

When a body is positively charged, its mass slightly decreases. When a body is negatively charged, its mass slightly increases.

Special Cases:

In the case of a conductor, its charge spreads over the entire outer surface and in the case of an insulator, its charge is localised.
The electric charge given to a conductor always resides on the outer surface of the conductor.

Read More: Conductors and Insulators

Charging of Bodies

The process of making a neutral body into a charged body is known as electrification. Electrification is a universal phenomenon.

A body can be electrically charged in any one of the following three ways:

Friction
Contact
Electrostatic induction

Charging by Friction

The electricity (i.e., transfer of electrons) that is produced due to friction is called frictional electricity.

Process of Charging

When we rub two neutral bodies, there will be some transfer of electrons from one body to the other due to structural modifications because of the frictional forces acting on them.

In this method, one of the bodies acquires a negative charge while the other gets a positive charge, both of which are equal in magnitude.

Examples

When a glass rod is rubbed with a silk cloth, glass acquires a positive charge and silk cloth acquires a negative charge. Electrons are removed from the glass rod and added to the silk cloth.
When an ebonite rod is rubbed with fur cloth, the ebonite rod acquires a negative charge, and the fur cloth acquires a positive charge. Electrons are transferred from the fur cloth to the ebonite rod.

Electric Series

The substances mentioned below are called electric series, and they are arranged in such a manner that if any two of them rubbed together, the one occurring earlier would be positively charged.

Glass, Flannel, Wool, Silk, Sealing Wax, Hard metal, Hard rubber, Resin, Sulphur, etc.

Explanation: If we select glass and silk, the glass will acquire a positive charge, while silk will get a negative charge when a glass rod is rubbed with silk.

Charging by Contact

A neutral body can be charged by making contact with a charged body. Here, the body will acquire a charge that is the same as that of the charging body. Thus, by contact, a similar charge is formed on both bodies. In this method, the electric charge on the first body decreases.

Charging by Electrostatic Induction

An induction always precedes attraction. The polarisation of charges in a body when a charged body is present near that is called induction. In induction, a charged body is brought near an uncharged body. Then, the uncharged body acquires a charge opposite in sign to that of the charged body.

Induced charge on a dielectric slab of dielectric constant K is

\(\begin{array}{l}{{q}^{1}}=-q\left[ 1-\frac{1}{K} \right]\end{array} \)

Without a decrease in charge of the body, which induces by the method of induction, bodies can be charged continuously.

Video Lessons

Electric Potential Energy

Electric Flux

Electric Charge and Methods of Charging, Electric Fields

Frequently Asked Questions on Electric Charge

What are the two types of charges?

Positive and negative are the two types of charges.

What is the charge of the proton when compared to the electron?

The charge of the proton is equal to that of an electron in magnitude but opposite in charge.

Do charged particles attract lighter uncharged bodies?

Yes, a charged particle can attract lighter uncharged bodies.

What is charging by conduction?

The process of charging a neutral conductor by bringing it into contact with the charged body is called charging by conduction.

What is charging by induction?

Charging a conductor by bringing a charged body close to it but not in contact with the conductor is called induction.

Electric Charge Definition and Properties