Calculation
F = k·q1·q2/r², k=1/(4πε0)≈8.988×10⁹ N·m²/C²
Like charges repel and unlike charges attract; force falls with the square of separation.
Busch 2006, Abschnitt 1.3.5, Gl. (1.56) Coulombsches Gesetz
Force between two point charges (Coulomb's law)
Like charges repel and unlike charges attract; force falls with the square of separation.
MINTSI
02
Result
Select a target and calculate.
Understand the inputs
- Coulomb force F — Magnitude of the force with which the two charges attract or repel.
- Charge q1 — Magnitude of the first point charge.
- Charge q2 — Magnitude of the second point charge.
- Separation r — Distance between the two charges, assumed point-like.
Example
q1=q2=1 µC at r=10 cm give F≈0.8988 N.
Assumptions and limits
Point-like, stationary charges in vacuum or air (εr≈1); extended charge distributions, dielectric surroundings and moving charges are excluded.
Understand Force between two point charges (Coulomb's law)
This calculator determines the electrostatic force between two point charges, the fundamental force law of the electric field and the basis for field-strength and potential considerations.
What does this quantity describe?
Two point charges q1 and q2 separated by r exert force F=k·q1·q2/r² on each other, with k=1/(4πε0)≈8.988×10⁹ N·m²/C². Like charges repel, unlike charges attract.
Formula and variables
F = k·q1·q2/r², k=1/(4πε0)≈8.988×10⁹ N·m²/C²
F = k·q1·q2/r²k = 1/(4πε0) ≈ 8.988×10⁹ N·m²/C²
| Symbol / input | Meaning |
|---|---|
| Coulomb force F | Magnitude of the force with which the two charges attract or repel. |
| Charge q1 | Magnitude of the first point charge. |
| Charge q2 | Magnitude of the second point charge. |
| Separation r | Distance between the two charges, assumed point-like. |
Choose the inputs correctly
q1 and q2 are the magnitudes of the two point charges, r their separation.
How to use the calculator
Enter charge magnitudes and separation in consistent units; charge sign only determines direction, not the force magnitude output here.
Worked example
q1=q2=1 µC at r=10 cm give F≈0.8988 N.
Understand the result and units
Doubling separation quarters the force; doubling one charge doubles it.
q1 and q2 are electric charges, r a length. F is output as a force.
Typical applications
Fundamental electrostatics, estimating forces between charged components, and a starting point for calculating electric field strength.
Assumptions, limits and common mistakes
Point-like, stationary charges in vacuum or air (εr≈1); extended charge distributions, dielectric surroundings, moving charges and relativistic effects are excluded.
Common mistake: Do not enter separation in the wrong unit; even small errors in separation affect the result quadratically.
Frequently asked questions
What is “Force between two point charges (Coulomb's law)” used for?
Fundamental electrostatics, estimating forces between charged components, and a starting point for calculating electric field strength.
Where do the input values come from?
q1 and q2 are the magnitudes of the two point charges, r their separation.
What does the result not cover?
Point-like, stationary charges in vacuum or air (εr≈1); extended charge distributions, dielectric surroundings, moving charges and relativistic effects are excluded.