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Coulomb's law

Statement

F=k∣q1q2∣r2F = k\dfrac{|q_1 q_2|}{r^2} — the interaction force between two point charges q1,q2q_1, q_2 separated by rr, with k≈9×109 N⋅m2/C2k \approx 9 \times 10^9\ \text{N·m}^2/\text{C}^2.

Why is it true?

Like charges repel, unlike charges attract; the force falls off with the square of distance, the same form as Newtonian gravity.

Move two charges q₁, q₂ in 3D and flip signs/magnitudes: F = k·|q₁q₂|/r² falls off as the square of distance and reverses when signs change.

Stated by

Topics that use this theorem

Step-by-step proofs

No step-by-step proof yet for this theorem.

References

  1. Charles-Augustin de Coulomb (1785). Premier mémoire sur l'électricité et le magnétisme