Coulombs Law

vCalc Reviewed
Equation / Last modified by KurtHeckman on 2018/03/15 18:32
vCalc.Coulombs Law

The Coulomb's Law calculator computes the force between two objects based on their charges, the distance between the objects, and the Coulomb Constant which is a function of the medium such as air or in this case a vacuum.

INSTRUCTIONS: Choose your preferred units and enter the following:

  • (q1) This is the charge of the first object.
  • (q2) This is the charge of the second object.
  • (r) - This is the distance between charges

Magnetic Force:  The calculator returns the force in newtons (N).  However, this can be automatically converted to other force units via the pull-down menu.

The Math / Science

Coulomb's Law describes the electrostatic interactions between two oppositely charged particles. The greater the charge on the ions and the smaller the ions are, the stronger the ionic bonding. The force is attractive if the charges are of different signs, and repulsive if they have the same sign. The Coulomb's Law Magnetic Force equation is as follows:

      |F| = k(|q+|·|q-|) / d² 


  • F is the magnetic force between particles
  • k This constant, `k_e`, is given by:
    `k_e =  1/ (4*pi*epsilon_0)`, where `epsilon_0` is the electric permittivity of free space
  • q+ is the charge of body 1 
  • q- is the charge of body 2 
  • d is the separation distance between the two centers of the particles

Both q+ and q- have units of Coulombs and d has default units of meters (m).

Supplemental Materials

Khan Academy: Coulomb's Law (with example)

Physics Classroom: Coulomb's Law


Whitten, et al. "Chemistry" 10th Edition. Pp. 253