Question 1

What is Coulomb's Law?

Accepted Answer

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.

Question 2

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

Accepted Answer

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.

Question 3

What does a positive vs. negative force mean?

Accepted Answer

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).

Question 4

Why are charges measured in such small numbers?

Accepted Answer

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).

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

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