# Coulomb's Law Calculator (F = kq₁q₂/r²)

Calculate electrostatic force between two charges using Coulomb's Law F = kq₁q₂/r². Determines force magnitude and whether it is attractive.

## What this calculates

Coulomb's Law describes the electrostatic force between two point charges. Like charges repel and unlike charges attract, with a force proportional to the product of the charges and inversely proportional to the square of the distance between them: F = kq₁q₂/r², where k = 8.988 × 10⁹ N·m²/C².

## Inputs

- **Charge 1 (q₁)** (C) — Use negative values for negative charges
- **Charge 2 (q₂)** (C)
- **Distance Between Charges (r)** (m) — min 0

## Outputs

- **Electrostatic Force** (N) — F = kq₁q₂/r² (positive = repulsive, negative = attractive)
- **Force (scientific notation)** (N) — formatted as text — Force in scientific notation
- **Force Magnitude** (N) — |F| — absolute value of the force
- **Force Type** — formatted as text — Attractive (opposite charges) or Repulsive (same charges)

## Frequently Asked Questions

**Q: What is Coulomb's Law?**

A: Coulomb's Law states that the force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them: F = kq₁q₂/r². It was discovered by Charles-Augustin de Coulomb in 1785 and is fundamental to electrostatics, much like Newton's gravitational law is to gravity.

**Q: How is Coulomb's Law similar to Newton's gravitational law?**

A: Both follow an inverse-square law: force ∝ 1/r². Both are proportional to the product of two quantities (charges or masses). However, gravity is always attractive, while the electrostatic force can be either attractive or repulsive. Also, the electrostatic force is about 10³⁶ times stronger than gravity for elementary particles.

**Q: What does a positive vs. negative force mean?**

A: In this calculator, a positive force means the charges repel each other (both positive or both negative). A negative force means the charges attract each other (one positive, one negative). The sign convention follows from the product q₁q₂: same-sign charges give a positive product (repulsion), opposite-sign charges give a negative product (attraction).

**Q: Why are charges measured in such small numbers?**

A: The Coulomb is an enormous unit of charge. One Coulomb contains about 6.24 × 10¹⁸ elementary charges (electrons or protons). The force between two 1 C charges at 1 m apart would be about 9 billion Newtons. In practice, charges in physics problems are typically microcoulombs (μC = 10⁻⁶ C) or nanocoulombs (nC = 10⁻⁹ C).

---

Source: https://vastcalc.com/calculators/physics/coulombs-law
Category: Physics
Last updated: 2026-04-21