Electrical charges show one of the four fundamental forces. Electrical charges will attract and repel each other depending on their charge; equal charges repel, different charges attract. The law to calculate electrical repulsion is called Coulomb's Law, and its equation uses a constant also called the Coulomb's constant. Calculating the Force of Repulsion between electrical charges is the first step to solve problems involving charges, magnetic fields, energy and work.
Things You'll Need
 Calculator

Write down your two electrical charges. For example, Q1 = First electrical charge and
Q2 = Second electrical charge.

Write down the distance between the two charges squared, which is D^2 = Distance between the two charges squared.

Write down your equation. The Equation is:
Repulsion Force = [ ( Kc ) x ( Q1 ) x ( Q2 ) ] / ( D^2 )
Where:
Kc = Coulomb's constant and the Coulomb Constant is 8.9876 x E^9 in the MKS system.

Replace your numbers in the equation and solve with the calculator.
For example:
Q1 = 9 x E^4
Q2 = 12 x E^5
D = 1, D^2 = 1
Repulsion Force = [ ( 8.9876 x E^9 ) x ( 9 x E^5 ) x ( 12 x E^5 ) ] / ( 1 )
After solving operations in the calculator:
Repulsion Force = 97.066 Newtons
Tips & Warnings
 One of the conclusions from Coulomb's Law is that the magnitude of the repulsion force is equal to the magnitude of the attraction force.
References
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