Electrostatic force is the mutual attraction or repulsion between two static electric charges. It follows Coulomb’s law, which states that the force is directly proportional to the product of the charges and inversely proportional to the square of the distance separating them. Everyday encounters, from a spark when walking across a carpet to the dramatic flash of lightning, illustrate this fundamental principle.
Identify the magnitude of the first charge, q₁, from reliable experimental data or published research. Express the value in coulombs (C).
Similarly, obtain the magnitude of the second charge, q₂, in coulombs.
Measure the distance between the two charges at the moment the charges were recorded. Use meters (m) for the distance.
The electrostatic force is calculated with the equation:
F = k · (q₁ × q₂) / D²
where k = 8.987 × 10⁹ N m² C⁻² (often rounded to 9 × 10⁹). The resulting force is expressed in newtons (N).
Example: Suppose q₁ = 6 × 10⁻⁶ C, q₂ = 9 × 10⁻⁶ C, and D = 2 m.
F = (9 × 10⁹) · [(6 × 10⁻⁶)(9 × 10⁻⁶)] / (2²) = (9 × 10⁹) · (54 × 10⁻¹²) / 4 = 4.86 × 10⁻¹ N ≈ 1.215 × 10⁻⁵ N.
In scientific notation, 1.215 × 10⁻⁵ N equals 0.00001215 N.
