### Coulomb’s law :

Coulomb’s law calculates the electric force

*F*in newtons (N) between two electric charges*q*_{1}and*q*_{2}in coulombs (C)with a distance of

*r*in meters (m):*F*is the force on

*q*

_{1}and

*q*

_{2}measured in newtons (N).

*k*is Coulomb’s constant

*k*= 8.988×10

^{9}N⋅m

^{2}/C

^{2}

*q*

_{1}is the first charge in coulombs (C).

*q*

_{2}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

^{-5}C and 3×10^{-5}C with distance of 40cm between them.*q*

_{1 }= 2×10

^{-5}C

*q*

_{2 }= 3×10

^{-5}C

*r*= 40cm = 0.4m

*F*= k×q

_{1}×q

_{2 }/ r

^{2}

= 8.988×10

^{9}N⋅m^{2}/C^{2}× 2×10^{-5}C × 3×10^{-5}C / (0.4m)^{2} = 37.705N