Electric charge is a fundamental property of matter that produces electromagnetic interaction. This guide covers what charge is, how to measure it, and real‑world uses.
What is Electric Charge?
Subatomic property with two types: positive and negative. Like charges repel; opposite charges attract.
Key Concept
Elementary charge e ≈ 1.602×10⁻¹⁹ C. Proton: +e; electron: −e; neutron: 0.
Measuring Electric Charge
Common units:
- Coulomb (C) — SI unit
- Millicoulomb (mC) — 0.001 C
- Microcoulomb (μC) — 0.000001 C
- Nanocoulomb (nC) — 10⁻⁹ C
- Elementary charge (e) — 1.602×10⁻¹⁹ C
Types of Electric Charge
Positive Charge
- Carried by protons
- Electron deficiency
- Attracts negative charge
- Repels positive charge
Negative Charge
- Carried by electrons
- Electron excess
- Attracts positive charge
- Repels negative charge
How is Electric Charge Measured?
- Electrometers — measure charge or potential
- Coulomb meters — direct charge measurement
- Integrating ammeters — integrate current over time
- Electroscopes — detect static
Did You Know?
Electrostatics studies stationary charges; electrodynamics studies moving charges. Lightning is a dramatic example.
Charge Carriers in Different Materials
Conductors
Allow charge to flow freely. Examples:
- Metals (Cu, Ag, Au, Al)
- Graphite
- Plasma
- Ionized gases
Insulators
Resist charge flow. Examples:
- Rubber
- Glass
- Plastic
- Ceramic
- Dry wood
Semiconductors
Intermediate conductivity. Examples:
- Silicon
- Germanium
- Gallium arsenide
Applications of Electric Charge
Everyday Life
- Static cling
- Batteries & portables
- Lightning protection
- Photocopiers & laser printers
Industrial & Scientific
- Electrostatic precipitators
- Electron microscopes
- Particle accelerators
- Semiconductor fabrication
Conservation of Charge
Total charge in an isolated system is constant—charge transfers but is neither created nor destroyed.
Practical Tip
Ground yourself when handling sensitive electronics to avoid ESD damage (use anti‑static wrist straps).