Coulomb's Law Calculator: Force Between Charges, Electric Field, Potential and Energy
Find the electric force, field and potential for two point charges.
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How this calculator works
Enter the two charges in microcoulombs (negative for a negative charge) and the distance in centimetres.
The calculator gives the size and direction of the force, the field of each charge at the other, the potential and the potential energy.
Formulas used
- F = \frac{k|q_1q_2|}{r^2},\quad k = 8.988\times10^9
- E = \frac{k|q|}{r^2}
- V = \frac{kq}{r}
- U = \frac{kq_1q_2}{r}
Worked example
With the default numbers in the calculator above:
- Size of the force between the charges (Coulomb's law): 0.60 N
- Direction: The charges repel each other (they have the same sign)
- Electric field of the first charge at the distance of the second: 1.9972e+5 N/C (V/m)
- Electric field of the second charge at the distance of the first: 2.9959e+5 N/C
- Electric potential of the first charge at that distance: 59917 V
- Electric potential energy of the pair: 0.17975 J
Change the numbers in the calculator to see the full working, every step, for your own case.
Common questions
What does Coulomb's law say?
The force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance between them.
Do like charges attract?
No. Like charges repel and unlike charges attract.
What is the value of k?
k = 1 / (4 pi epsilon0) = 8.988 x 10 to the 9 N m squared per coulomb squared in a vacuum.
What happens if I double the distance?
The force falls to a quarter, because it depends on the square of the distance.
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Got a question about this? Ask an engineering question and get a plain-language answer with references.
Further reading: Any first-year physics text (electrostatics).
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