Coulomb's Law Equation Calculator

Solve Coulomb law cases with detailed steps. Switch variables, units, and media quickly for learning. Download force, field, energy, and comparison results instantly today.

Calculator Inputs

Formula Used

The main equation is F = k |q1 q2| / (εr r²).

Here, F is electrostatic force in newtons. q1 and q2 are charges in coulombs. r is separation in meters. k is Coulomb constant. εr is relative permittivity.

Reverse forms used by this calculator include q = F εr r² / (k |other charge|), r = √(k |q1 q2| / (εr F)), and εr = k |q1 q2| / (F r²).

Extra outputs use E = k |q1| / (εr r²), V = k q1 / (εr r), and U = k q1 q2 / (εr r).

How to Use This Calculator

  1. Select the unknown value from the solve menu.
  2. Enter the known charges with correct signs and units.
  3. Enter distance, known force, relative permittivity, and constant.
  4. Use reverse interaction when solving a missing charge.
  5. Press Calculate to place the result above the form.
  6. Use CSV or PDF buttons to save the completed result.

Example Data Table

q1 q2 Distance εr Force Type
2 µC 3 µC 0.05 m 1 21.5701 N Repulsive
-4 µC 1.5 µC 0.10 m 1 5.3925 N Attractive
5 nC -8 nC 0.02 m 2.2 0.0004085 N Attractive
1 mC 2 mC 1.00 m 80 224.6888 N Repulsive

Coulomb Law Calculator Guide

Why This Tool Matters

Coulomb law explains how two charged objects pull or push each other. The calculator helps learners test that relationship without losing track of units. It is useful for homework, lab notes, electronics review, and quick checking before a longer solution. Because charge values are often tiny, the tool accepts common charge units and converts them to coulombs before solving.

What The Result Shows

The result panel gives the selected unknown first. It also reports force magnitude, signed force, interaction type, vacuum comparison, electric field, potential, and potential energy when enough data exists. A positive charge product means repulsion. A negative product means attraction. The dielectric value reduces the interaction when the space between charges is not a vacuum. Air is close to one, while water is much higher.

Good Input Practice

Use signed charge values when direction matters. Enter positive charge for protons or positively charged bodies. Enter negative charge for electrons or negatively charged bodies. Distance must be greater than zero. Relative permittivity should also be greater than zero. When solving for a missing charge, choose whether the interaction is repulsive or attractive. That choice controls the sign of the unknown charge.

Learning With Examples

Try the example table before using your own data. Notice how doubling the distance makes the force one fourth as large. Notice how increasing relative permittivity lowers force. This inverse square pattern is the main lesson behind the equation. It also explains why nearby charges can create strong effects, while far charges quickly become weak.

Using Results Responsibly

This calculator is a learning and estimation tool. Real systems may include many charges, irregular shapes, shielding, grounding, and changing materials. For advanced physics or engineering work, compare the result with a complete model. Still, the equation remains a powerful starting point. It shows how charge size, separation, and medium quality control electrostatic behavior. Keep units consistent, read each step, and export results for records.

Exported files can help compare attempts. The CSV file suits spreadsheets. The PDF file suits reports. Save input values beside answers. This makes errors easier to find later. Recalculate after changing one value at a time, so each physical effect stays visible onscreen.

FAQs

What does Coulomb law calculate?

It calculates electrostatic force between two point charges. The answer depends on charge size, distance, Coulomb constant, and the medium between charges.

Can this tool solve for missing charge?

Yes. Select q1 or q2 as the unknown. Enter force, the other charge, distance, relative permittivity, and interaction type.

Why are signs important for charges?

Signs show whether charges attract or repel. Same signs repel. Opposite signs attract. Force magnitude is always reported as positive.

What is relative permittivity?

Relative permittivity describes how a medium weakens electric force. A larger value lowers force compared with the same charges in vacuum.

Which units should I use?

You may enter charges in C, mC, µC, nC, or pC. Distance and force also include common unit choices.

Why does distance affect force strongly?

Coulomb law follows an inverse square relationship. If distance doubles, force becomes one fourth, when other values stay unchanged.

What do electric field and potential mean?

Electric field shows force per unit charge. Electric potential shows energy per unit charge from the selected source charge.

Are CSV and PDF downloads included?

Yes. After calculation, use the download buttons in the result panel to save the answer table as CSV or PDF.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.