Enter your two charges (q₁ and q₂) and the distance (r) between them, and this Coulomb's Law Calculator computes the electrostatic force acting between them — plus whether that force is attractive or repulsive, with full unit flexibility for each input.
Electrostatic Force
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Force Type
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Coulomb's Constant
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Use Coulomb's law: F = k × |q₁ × q₂| / r². Enter the charges, distance, and select appropriate units. The calculator will determine if the force is attractive (opposite charges) or repulsive (like charges).
Yes, Coulomb's law is an inverse square law. The electrostatic force is inversely proportional to the square of the distance between charges. Doubling the distance reduces the force to one-fourth of its original value.
In a hydrogen atom, the proton (+1.6 × 10⁻¹⁹ C) and electron (-1.6 × 10⁻¹⁹ C) are separated by about 5.3 × 10⁻¹¹ m. This results in an attractive force of approximately 8.2 × 10⁻⁸ N.
The force is attractive when charges have opposite signs (+ and -) and repulsive when charges have the same sign (both + or both -). The calculator automatically determines this based on your input values.
For charges: coulombs (C), millicoulombs (mC), microcoulombs (µC), nanocoulombs (nC), and picocoulombs (pC). For distances: meters (m), centimeters (cm), millimeters (mm), micrometers (µm), and nanometers (nm).
Coulomb's constant (k) is approximately 8.99 × 10⁹ N⋅m²/C². This fundamental constant relates the electrostatic force to the charges and distance in Coulomb's law equation.
Coulomb's law applies to point charges or spherically symmetric charge distributions in a vacuum. It's most accurate when charges are stationary and the distance between them is much larger than their physical size.