One of the most basic ideas in physics is electric charge. It is essential to our understanding of the interactions between matter and the operation of electric and magnetic fields. From the electricity that runs your phone to the static jerk you get when you touch a doorknob, you come into contact with electric charge on a daily basis.
What is Electric Charge?
When matter is exposed to an electric or magnetic field, it experiences a force due to its electric charge.
There are two kinds: positive and negative.
Positive charge is the kind of charge carried by protons, while negative charge is carried by electrons.
An object is considered neutral when its positive and negative charges are equal.
Basic Properties of Electric Charge
1.Quantization of Charge
Charge is quantized, which means it always comes in fixed amounts. The smallest possible unit of charge is the charge of an electron or proton, denoted as e.
Where
e = 1.6 × 10⁻¹⁹ C (Coulombs).
Any charge (q) is a multiple of this unit:
q = n × e, where n is an integer (can be positive or negative).
2. Conservation of Charge
Charge can neither be created nor destroyed. It can only be transferred from one body to another. The total charge in an isolated system always remains constant.
3. Additive Nature of Charge
Charges can be added algebraically. If an object has +3e and another has -2e, the total charge is (+3e) + (-2e) = +1e.
4. Like Charges Repel, Unlike Charges Attract
This is a very important rule:
Positive charge repels positive
Negative charge repels negative
Positive attracts negative (and vice versa)
How Does a Body Get Charged?
There are three main methods of charging a body:
1.Friction: Electrons can be transferred between two things by rubbing them together. For example, when we rub a balloon against our hair, our hair becomes positively charged and the balloon becomes negatively charged.
2. Conduction: A portion of the charge moves to the neutral body when a charged body comes into contact with it.
3. Induction: Without making physical touch, a charged object can cause another object nearby to become charged as well.
When an object looses some electrons, it become positively charged and becomes negatively charged if an object gains some electrons.
When a glass rod( or cat’s fur) is rubbed with silk or plastic rod then both acquire opposite charge. By convention, the charge on glass rod or cat’s fur is called positive and that on plastic rod or silk is termed as negative. If an object possesses an electric charge, it is said to be electrified or charged. When it has no charge it is to be neutral.
Coulomb’s Law
The force between two charges is given by Coulomb’s Law. It states:
“The force of attraction or repulsion between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.”
Mathematically:
F = (1 / 4πε₀) × (q₁q₂ / r²)
Where:
F is the force
q₁ and q₂ are the charges
r is the distance between them
ε₀ is the permittivity of free space
(ε₀ ≈ 8.85 × 10⁻¹² C²/N·m²)
This force acts along the line joining the two charges.
Point charge: Charge located at a single point.
Line charge: Charge distributed along a line (like a charged wire).
Surface charge: Charge spread over a surface.
Volume charge: Charge spread throughout a volume (like inside a cloud).
Summary
A fundamental component of electromagnetic, electric charge is essential to understand the functioning of the world on both, a large and microscopic scale.
This small characteristic results in some of the strongest forces we are aware of, from atoms to electric circuits. All of the complex issues in electricity and magnetism have a solid basis once we understand the fundamentals of types, conservation, quantization, and interaction.
Sl no | Questions | Answers |
1. | What is an electric charge? | A physical property of matter that causes it to experience a force in an electric or magnetic field. It can be positive (proton) or negative (electron). |
2 | What is meant by the quantization of charge? | Charge exists in discrete units and is always a multiple of the elementary charge (e = 1.6 × 10⁻¹⁹ C). |
3 | How is charge transferred from one body to another? | 1. Friction – rubbing transfers electrons2. Conduction – direct contact3. Induction – influence without contact. |
4 | What is Coulomb’s Law? | F = (1 / 4πε₀) × (q₁q₂ / r²) |
5 | What is the difference between conductors and insulators? |
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6 | Can electric charge be created or destroyed? | No. According to the law of conservation of charge, charge can only be transferred, not created or destroyed. |
7 | Why don’t we observe fractional charges in real life? | Because only whole number multiples of e are observed. Though particles like quarks have fractional charges, they’re never found alone in nature. |
When matter is in an electric or magnetic field, its physical characteristic known as electric charge causes it to feel a force. It can be either negative (like electrons) or positive (like protons). While objects with the same charge repel one another, those with opposite charges are attracted to one another.
Quantization of charge means that charge only exists in discrete packets. The smallest unit of charge is the charge of an electron (e = 1.6 × 10⁻¹⁹ C). So, any charge (q) must be a whole number multiple of e, i.e., q = n × e, where n is an integer.
Charge can be transferred in three main ways:
Friction – By rubbing two objects transfers electrons.
Conduction – By direct contact allows charge to flow.
Induction – A charged object induces opposite charge in a nearby object without touching it.
The force between two point charges is provided by Coulomb’s Law. According to this, the electrostatic force is inversely proportional to the square of the distance between two charges and directly proportional to the product of the two charges:
F = (1 / 4πε₀) × (q₁q₂ / r²)
Conductors, permit the free flow of electric charges, often electrons such as metals like copper.
• Insulators, prevent charges from moving freely. They have fixed positions for their charges (such as rubber or plastic).
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