PhysicsChapter 6: Electrostatics
Coulomb's Law
Introduction
Coulomb's law describes the electric force between two point charges. The magnitude is: F = k|q₁q₂|/r² where: `F` = electrostatic force; `q₁`, `q₂` = charges; `r` = separation; `k ≈ 8.99 × 10⁹ N m² C⁻²` in vacuum.
Definition
Meaning
Greater charges → stronger force. Greater distance → weaker force. Because: **F ∝ 1r²** doubling separation reduces force to one quarter.
Direction
Like charges repel. Unlike charges attract. The force acts along the line joining the two charges.
Worked Example
`q₁ = 2 μC` `q₂ = 3 μC` `r = 0.20 m` Convert: `2 μC = 2×10⁻⁶ C` `3 μC = 3×10⁻⁶ C` Then: `F = (8.99×10⁹)(2×10⁻⁶)3×10⁻⁶0.20²` `F ≈ 1.35 N`
Did you understand this topic?
Your answer is saved with your learning record. It does not mark the topic as mastered.
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Coulomb's Law
Sticky Notes · Quick Revision
COULOMB
- `F = k|q₁q₂|/r²`
DOUBLE r
- Force → 14