Coulomb's Law Calculator

Calculate electrostatic force between two point charges. Supports metric units with automatic unit conversion. Essential for physics and electrical engineering.

Charge 1 (q₁)

Charge 2 (q₂)

Distance (r)

Results

Force (F): 8.99e9 N

Nature: Repulsive

Intermediate values:

q₁ (C): 1e-6 C

q₂ (C): 1e-6 C

r (m): 0.001 m

Understanding Coulomb's Law

Coulomb's Law describes the electrostatic force between two charged particles. It's fundamental for understanding electromagnetic phenomena and is crucial in fields ranging from particle physics to electrical engineering.

Calculation Steps:

Convert both charges to Coulombs (SI unit)
Convert distance to meters (SI unit)
Apply Coulomb's formula: F = k·q₁·q₂/r²
Determine force direction (attractive for opposite charges, repulsive for like charges)

Examples:

Two 1μC charges 1mm apart: 8.99 N repulsive force
+2μC and -3μC charges 5cm apart: 21.57 N attractive force
Two 1nC charges 10cm apart: 899 μN repulsive force

Reference Values:

Charge Level	Typical Context
1 nC	Electrostatic discharge
1 μC	Capacitor storage
1 mC	Lightning bolt (approximate)

Important Notes:

Valid for point charges in vacuum/air
Different dielectric materials affect force (use relative permittivity)
For large distances, relativistic effects may apply

Force vs Distance

Drag to see how force changes with distance (current charges remain fixed):

Distance: 1.0 mm

Force at this distance: 89.9 N

Frequently Asked Questions

Why is my calculated force so large?

Coulomb forces are extremely strong at small distances. A 1μC charge at 1mm produces nearly 9000N of force - enough to lift a small car!

Does this work for non-spherical charges?

Coulomb's Law applies exactly only to point charges. For complex shapes, integration over charge distributions is needed.

Why use different charge units?

A Coulomb is extremely large for most electrostatic applications. Microcoulombs (μC) and nanocoulombs (nC) are more practical units.

Formulas & Assumptions

F = k × |q₁ × q₂| / r²

Where:
F = Electrostatic force (Newtons)
k = Coulomb's constant (8.9875517873681764 × 10⁹ N·m²/C²)
q₁, q₂ = Electric charges (Coulombs)
r = Distance between charges (meters)

Constants:
k = 1/(4πε₀) where ε₀ = 8.8541878128 × 10⁻¹² F⋅m⁻¹

Rounding: Results rounded to 3 significant figures
Nature: Determined by product of charges (positive = repulsive, negative = attractive)

Disclaimer: For educational and informational purposes only. Not intended for engineering design or critical systems. Actual forces may vary based on environmental conditions and charge distributions.

Sources:

SI Brochure: The International System of Units (SI)
NIST Reference on Constants, Units, and Uncertainty
ISO 80000-1:2009 Quantities and units

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