Coulomb's Law

• Coulomb's law formula
• Coulomb's law example

Coulomb's law formula

Coulomb's law calculates the electric force F between two electric charges q₁ and q₂ with distance of r:

 

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

 

---

See also

• Electric charge
• Current
• Ampere (amp)
• Voltage
• Capacitor
• Resistor
• Electronics units