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.
Definition
A fundamental property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).
💡 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.
Example
Notation
q or Q is electric charge in coulombs (C), e = 1.602 \times 10^{-19} C is the elementary charge, I is current in amperes, and t is time in seconds.
🌟 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.
💭 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.
Formal View
Related Concepts
See Also
🚧 Common Stuck Point
Protons don't move in circuits — it's electrons (negative charges) that flow through wires.
⚠️ Common Mistakes
- Thinking that charging an object creates new charge — charging only transfers electrons from one object to another; total charge is always conserved.
- Confusing coulombs with electrons — one coulomb equals about 6.24 \times 10^{18} electrons, so everyday charges in circuits are fractions of a coulomb.
- Forgetting the sign: electrons carry negative charge (-1.6 \times 10^{-19} C each), so a flow of electrons in one direction is a conventional current in the opposite direction.
Common Mistakes Guides
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).
When do you use Electric Charge?
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.
What do students usually get wrong about Electric Charge?
Protons don't move in circuits — it's electrons (negative charges) that flow through wires.
Next Steps
Cross-Subject Connections
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.