Electric charge is one of the most fundamental properties in nature. It is responsible for all electric and magnetic phenomena.
Basic Properties of Electric Charge
Two Types of Charges
There are exactly two types of electric charges:
Positive charge (like on a glass rod rubbed with silk)
Negative charge (like on an ebonite rod rubbed with fur)
We name them positive and negative just by convention. Protons carry positive charge, and electrons carry negative charge. Neutrons, on the other hand, are neutral (they have no charge).
Key point:
Like charges repel, unlike charges attract.
So, two positive charges will push each other away, and a positive and a negative charge will pull each other together.
Quantisation of Charge
Electric charge is quantised, meaning it comes in separate packets. The smallest unit of charge is the charge of an electron (or proton).
Charge on an electron, e = -1.6 × 10⁻¹⁹ coulombs.
Charge on a proton, e = +1.6 × 10⁻¹⁹ coulombs.
If an object has a total charge q, then:
q = ne
Where n is an integer (positive or negative), and e is the elementary charge.
In simple words:
We can only have charges like e,2e,3e,−e,−2e and so on, but never 1.5e or √2e.
Conservation of Charge
Electric charge can neither be created nor destroyed. It can only be transferred from one body to another.
In any isolated system, the total electric charge remains constant, no matter what processes are happening inside.
Examples:
In chemical reactions, charges move from one atom to another, but the total charge remains the same.
In nuclear reactions too, even if particles are split or combined, the net charge before and after the reaction stays the same
Additivity of Charge
Charges simply add up like regular numbers (scalars).
If we have multiple charges, the total charge is the algebraic sum of all individual charges.
Example:
A body with +3 C and another with -2 C will have a total charge of:
3 C + (−2 C) = 1 C
So, when dealing with multiple charges, we just need to add or subtract them depending on their sign.
Invariance of Charge
The value of electric charge is independent of the frame of reference or the speed of the charged object.
This means:
Whether a charged object is at rest or moving fast, its charge remains the same.
Even under Einstein’s theory of relativity, where mass and time can change at high speeds, electric charge remains constant.
In short: charge does not change with motion.
Attraction and Repulsion
Electric forces between charges are governed by
Coulomb’s Law:
Like charges repel each other.
Unlike charges attract each other.
The force between two charges depends on:
The magnitude of the charges
The distance between them
Greater the charge, greater the force. Greater the distance, lesser the force.
Final Quick Recap:
Property | Description |
Types of Charges | Positive and Negative |
Quantization | Charges exist in multiples of elementary charge (e) |
Conservation | Total charge remains constant in an isolated system |
Additivity | Charges add up like simple numbers |
Invariance | Charge doesn’t change with speed or frame of reference |
Interaction | Like charges repel, unlike charges attract |
In essence:
Electric charge is a basic building block of the universe, and these simple properties lay the foundation for understanding electricity, magnetism, and modern physics.
There are two types of electric charges: positive and negative. Positive charges repel other positive charges and attract negative charges, and vice versa.
Quantization of charge means that electric charge exists in discrete packets. Any charge q on a body is an integral multiple of the elementary charge e, where:
q = ne with n being an integer.
The charge on an electron is approximately:
−1.6 × 10−19 coulombs
It is the fundamental unit of negative charge.
The principle of conservation of charge states that electric charge can neither be created nor destroyed. The total charge in an isolated system remains constant over time.
No, electric charge is invariant. It does not change with the speed of the object or with the frame of reference, even at very high velocities close to the speed of light.
Charges interact according to these simple rules:
Like charges repel each other.
Unlike charges attract each other.