Physics / core

Electric Charge

Also known as: charge, coulomb

definition

A fundamental property of matter that causes it to experience a force in an electromagnetic field. Electric charge is the source of all electrical phenomena, from lightning strikes and static cling to the operation of every computer chip and battery.

💡 Intuition

Some particles carry an invisible 'label' — positive or negative — that makes them push or pull on each other.

Core Idea

Charge comes in two types (positive and negative) and is conserved — it can move but cannot be created or destroyed.

Formal View

Electric charge q is a fundamental conserved quantity. It is quantised in units of the elementary charge e = 1.602 \times 10^{-19} C. Charge obeys conservation: \sum q_{\text{before}} = \sum q_{\text{after}} in any process. The SI unit is the coulomb (C), defined as 1\text{ C} = 1\text{ A} \cdot 1\text{ s}.

🔬 Example

Rubbing a balloon on your hair transfers electrons, giving the balloon a negative charge that sticks to the wall.

🎯 Why It Matters

Electric charge is the source of all electrical phenomena, from lightning strikes and static cling to the operation of every computer chip and battery. Understanding charge is the starting point for all of electricity and magnetism.

⚠️ Common Confusion

Protons don't move in circuits — it's electrons (negative charges) that flow through wires.

💭 Hint When Stuck

When solving a charge problem, first identify whether charge is being transferred, conserved, or creating a force. Use Q = It to relate charge to current and time. If calculating force between charges, use Coulomb's law. Always check that total charge is conserved — charge cannot be created or destroyed.

Related Concepts

How Electric Charge Connects to Other Ideas

Once you have a solid grasp of electric charge, you can move on to electric current, electric field and coulombs law.

Go Deeper

Worked Examples

Step-by-step solved problems

Practice Problems

Test your understanding

Frequently Asked Questions

What is Electric Charge in Physics?

A fundamental property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).

Why is Electric Charge important?

Electric charge is the source of all electrical phenomena, from lightning strikes and static cling to the operation of every computer chip and battery. Understanding charge is the starting point for all of electricity and magnetism.

What do students usually get wrong about Electric Charge?

Protons don't move in circuits — it's electrons (negative charges) that flow through wires.