How to Calculate Force Between Two Charged Particles

When you rub a balloon against your hair, an electric force due to many charged particles causes your hair to stick to the balloon. The same type of force works on a much smaller scale between individual protons and electrons. These particles hold the smallest known electrical charge, called the fundamental charge. The fundamental charge is 1.6 x 10^-19 Coulombs; it is positive for protons but negative for electrons. Use Coulomb's law to calculate the electrical force between two particles.

Instructions

1. Multiply the charges of the two particles together. For example, if the particles are one electron and one proton, multiply -1.6 x 10^-19 Coulombs by 1.6 x 10^-19 Coulombs to get -2.56 x 10^-38 Coulombs squared.

2. Divide the result by the square of the distance between the particles in meters. If the particles are 0.01 meters apart, calculate (-2.56 x 10^-38 Coulombs squared)/(0.01 m)^2 to get -2.56 x 10^-34 Coulombs squared per square meter.

3. Multiply the result by the proportionality constant, 9 x 10^9 Newton-meters squared per Coulomb squared. For example, multiply -2.56 x 10^-34 Coulombs squared per square meter by 9 x 10^9 Newton-meters squared per Coulomb squared to get a force of 2.3 x 10^-24 Newtons.

4. Determine whether the force is attractive or repulsive. A negative result means the force attracts the particles toward each other, while a positive result means the force moves the particles away from each other.

References

• Georgia Perimeter College; Electric Charge and Electric Force; Martin Okafor; May 2009
• University of Rochester; Electric Force and Electric Charge; Frank Wolf

Resources

• eCalc.com: Online Scientific Calculator and Math Help