Coulomb's Law Calculator
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Other tools you may find usefulCoulomb's Law Calculator - Calculate the electrostatic force between charges
Calculate the electrostatic force between two electric charges. The Coulomb's Law calculator automatically converts values in newtons, takes into account the distance and type of charges. An excellent tool for learning physics, electrical engineering and materials engineering.
Run calculator Coulomb's See formulas and examples
What is Coulomb's Law
Coulomb's Law describes the force of electrostatic interaction between two point electric charges. This force is proportional to the product of the charges and inversely proportional to the square of the distance between them. It acts along the line connecting both charges - attracting or repelling depending on their signs.
Coulomb's Law formula
F = k · (|q₁ · q₂|) / r²
where:
F – electrostatic force [N]
k – electrostatic constant = 8.9875×10⁹ N m²/C²
q₁, q₂ – charge values [C]
r – distance between charges [m]For charges with the same sign (both positive or both negative), the force isrepulsive. For charges with opposite signs –attracting. The value of the force is always positive, the direction is determined by the action vector.
How to use the calculator
- Enter the values of the charges q₁ and q₂ in coulombs (C) or micro-/nano-coulombs.
- Enter the distance between them in meters.
- ClickCalculate– the calculator will return the force in newtons (N).
- The result takes into account the direction of the force - attraction or repulsion.
Calculation examples
Attraction of opposite charges
q₁ = 3×10⁻⁶ C, q₂ = -2×10⁻⁶ C, r = 0.1 m.
F = 8.9875×10⁹ × (6×10⁻¹²) / 0.01 =5.39 N(snapping).
Repulsion of positive charges
q₁ = 5×10⁻⁶ C, q₂ = 1×10⁻⁶ C, r = 0.2 m.
F = 8.9875×10⁹ × (5×10⁻¹²) / 0.04 =1.12 N(repulsion).
Smaller loads and long distance
q₁ = 1×10⁻⁹ C, q₂ = -1×10⁻⁹ C, r = 1 m.
F = 8.9875×10⁹ × (1×10⁻¹⁸) / 1 =8.99×10⁻⁹ N(snap).
Laboratory experiment
q₁ = 1×10⁻⁵ C, q₂ = -4×10⁻⁵ C, r = 0.5 m.
F = 8.9875×10⁹ × (4×10⁻¹⁰) / 0.25 =14.38 N(snap).
The vector version of the equation
𝐅₁₂ = k · (q₁q₂ / r²) · 𝐫̂The direction of the vector 𝐅₁₂ is along the straight line connecting the two charges. Changing the sign of one of the charges changes the direction of the force vector.
Electrostatic constant
Value of the electrostatic constant in vacuum:
k = 1 / (4π·ε₀) ≈ 8.9875517923×10⁹ N·m²/C²where ε₀ = 8.854×10⁻¹² F/m – electric permittivity of vacuum.
Frequently asked questions (FAQ)
What are the units of cargo?
The basic SI unit is the coulomb (C). 1 C = 1 A s. In practice, micro- or nano-coulombs are used.
Can force be negative?
The value of the force is always positive, but the directional sign determines the nature of the interaction - attraction or repulsion.
Does Coulomb's Law work in media other than vacuum?
Yes, with correction for the permittivity of the given medium:F = (1 / (4π·ε)) · (|q₁q₂| / r²).
How does distance affect force?
The force decreases inversely as the square of the distance - if r increases by a factor of two, the force will decrease by a factor of four.
Applications of Coulomb's Law
- Analysis of electrostatic interactions between particles.
- Modeling of capacitors and electric fields.
- Calculations in high voltage engineering.
- Molecular simulations in chemistry and quantum physics.
Summary:Coulomb's Law Calculator is a simple and precise tool for calculating the electrostatic force between charges. Just enter the charges and distance, and the calculator will return the result in newtons, along with information about the direction of impact.