Calculator Inputs
Formula Used
Electrostatic potential energy between two point charges:
U = (1 / (4π ε0 εr)) × (q1 q2 / r)
U = k × q1 q2 / (εr r)
Here, U is electrostatic potential energy, k is Coulomb's constant (8.9875517923 × 109 N·m²/C²), q1 and q2 are the charges in coulombs, r is separation distance in meters, and εr is the medium's relative permittivity.
Positive energy means the arrangement is repulsive. Negative energy means the arrangement is attractive. In chemistry-style problems, you may enter charge in elementary-charge units, where 1e = 1.602176634 × 10-19 C.
How to Use This Calculator
- Enter the first and second charge values.
- Select the correct unit for each charge.
- Enter the separation distance and choose its unit.
- Select a preset medium or choose custom permittivity.
- Pick the desired output energy unit and decimals.
- Click the calculate button to view results above the form.
- Review the graph to see how energy changes with distance.
- Use the CSV or PDF buttons to export the result summary.
Example Data Table
| Scenario | q1 | q2 | Distance | εr | Potential Energy (J) | Interaction |
|---|---|---|---|---|---|---|
| Opposite microcoulomb charges in air | 1.5000 μC | -2.0000 μC | 4.0000 cm | 1.0000 | -6.740664e-1 | Attractive |
| Like charges in a dielectric | 3.0000 μC | 3.0000 μC | 10.0000 cm | 2.5000 | 3.235519e-1 | Repulsive |
| Ion-style charges in water | 2.0000 e | -1.0000 e | 2.8000 Å | 78.5000 | -2.099252e-20 | Attractive |
Frequently Asked Questions
1. What does a negative potential energy result mean?
A negative value means the charges attract each other. The pair is at a lower-energy state than infinite separation, so energy would be needed to pull them apart completely.
2. What does a positive potential energy result mean?
A positive value means the charges repel each other. Work must be supplied to bring like charges together from very large separation.
3. Can I use ionic charges for chemistry problems?
Yes. Select the elementary-charge unit and enter values such as +1, +2, or -1. The calculator converts them into coulombs automatically.
4. Why does the medium change the answer?
The medium changes relative permittivity. Higher permittivity reduces the electrostatic interaction, so the magnitude of potential energy and force becomes smaller.
5. Why does the value grow rapidly at short distance?
Potential energy varies as 1/r. When the distance becomes very small, the magnitude rises sharply because the charges interact much more strongly.
6. Why is my result zero?
That usually happens when one charge is entered as zero. If either charge is zero, the pair has no electrostatic interaction energy in this two-particle model.
7. Is this calculator suitable for molecules and real materials?
It is best for simplified point-charge estimates. Real molecules can include geometry, shielding, polarization, and quantum effects that are not modeled here.
8. What do the CSV and PDF downloads include?
They export the current input values and computed results, including energy, force, electric potential, interaction type, and interpretation text for quick sharing.