Coulomb's Law
Also known as force between two charges · electrostatic force
Worked example: Two 1 uC charges 1 m apart → 8.98755 mN — press Try an example to run it live, then adjust anything.
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Coulomb's count →
Grade 12Grade 12 Physics
Coulomb's Law →
UniversityCircuits & Electrical Power
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Coulomb's Law explained
In 1785 Charles-Augustin de Coulomb hung a charged sphere on a fine torsion wire and measured how hard a second charge twisted it. The result is the electric twin of Newtonian gravity: the force between two point charges grows with the product of the charges and falls off with the square of the distance. Electricity is by far the stronger force: the electric repulsion between two protons is about 10³⁶ times their gravitational attraction — which is why a rubbed balloon can lift paper against the pull of the entire Earth.
Worked example: two 1 µC charges held 10 cm apart feel F = kₑ × (10⁻⁶)² / (0.1)² ≈ 0.9 N — roughly the weight of an apple, from specks of charge. Enter charge magnitudes here; the sign of the product only tells you whether the pair attracts (opposite signs) or repels (like signs).
Coulomb's Law formula
- = Electrostatic force (N)
- = Charge 1 (C)
- = Charge 2 (C)
- = Separation distance (m)
Missing one of these? Work it out first, then come back
- Electrostatic force — Newton's Second Law, Force Between Parallel Wires
- Charge 1 — Electric Charge (Q = It), Number of Elementary Charges (N = Q/e)
- Charge 2 — Electric Charge (Q = It), Number of Elementary Charges (N = Q/e)
- Separation distance — Speed, Distance & Time, Force Between Parallel Wires