Coulomb's Law And Formula With Example

Coulomb's law 

     "The magnitude of the electrostatic force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distance between them".

Coulomb's law Formula

Coulomb's law calculates the electric force F in newtons (N) between two electric charges q1 and q2 in coulombs (C)

with a distance of r in meters (m)

 F is the force on q1 and q2 measured in newtons (N).

k is Coulomb's constant k = 8.988×109 N·m2/C2

q1 is the first charge in coulombs (C).

q2 is the second charge in coulombs (C).

r is the distance between the 2 charges in meters (m).

When charges q1 and q2 is increased, the force F is increased.

When distance r is increased, the force F is decreased.

Coulomb's law example

Find the force between 2 electric charges of 2×10-5C and 3×10-5C with distance of 40cm between them.

q1 = 2×10-5C

q2 = 3×10-5C

r = 40cm = 0.4m

F = k×q1×q2 / r2 = 8.988×109N·m2/C2 × 2×10-5C × 3×10-5C / (0.4m)2 = 37.705N