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Physics
Coulomb’s law
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AttractionF = 1 F₀
F₁ = F₂ = N
Drag q₁ away
Charge symbols are enlarged · Arrow length is proportional to force
Double the force and the arrow doubles in length. Dashed arrows show the reference force F₀.
µC
µC
Each situation starts from the default setup.
cm
cm
Display options
F₀ uses the initial setup. Keep a new reference, then change one variable to compare.
Force on each object
F = k |q₁q₂| / r²
F = 8.99 × 10⁹ × |(−4 × 10⁻⁶)(8 × 10⁻⁶)| / (0.03)² ≈ 319.6 N
Textbooks round k ≈ 9 × 10⁹ N·m²/C².
F₁ and F₂ have equal magnitudes and opposite directions. They act on different objects.
How the quantities relate
Double one charge: the force doubles. Double the distance while keeping the charges: the force becomes one quarter.
Model notes
- Two ideal point charges held at fixed positions in vacuum; the spheres and arrows are schematic, not a motion simulation.
- r is measured between centres. Atomic mode uses elementary-charge units e and picometres (pm); it remains a classical model, not a quantum description of atoms.
- The model uses k = 8.987551 × 10⁹ N·m²/C² and e = 1.6021766208 × 10⁻¹⁹ C.