Coulomb Calculator

Calculation Type:

Force (N):

Charge 1 (C):

Charge 2 (C):

Distance (m):

Medium:

Understanding the forces between electric charges is fundamental to physics and electrical engineering. Coulomb’s Law describes the electrostatic force between two charged particles. However, manually calculating force, charge, or distance can be tricky and prone to errors.

Our Coulomb Calculator simplifies this by letting you compute force (F), charge 1 (q₁), charge 2 (q₂), or distance (r) based on the inputs you provide. It also allows selecting the medium to account for different permittivity values, which affects the Coulomb constant (k).

Whether you are a student, teacher, or engineer, this tool provides fast, accurate calculations with a user-friendly interface.

What is Coulomb’s Law?

Coulomb’s Law states: $F = k \frac{|q_1 q_2|}{r^2}$ F=kr2∣q1q2∣

Where:

$F$ F = electrostatic force (Newtons, N)
$q_1$ q1, $q_2$ q2 = magnitudes of the two charges (Coulombs, C)
$r$ r = distance between charges (meters, m)
$k$ k = Coulomb constant, depends on the medium

The constant $k$ k equals approximately $8.99 \times 10^9 \, \text{N·m}^2/\text{C}^2$ 8.99×109N\cdotpm2/C2 in vacuum or air, but varies with the material between the charges.

How to Use the Coulomb Calculator

Step 1: Select the Calculation Type

Choose which quantity you want to calculate:

Force (F)
Charge 1 (q₁)
Charge 2 (q₂)
Distance (r)

Step 2: Enter Known Values

Based on your selection, input the known values into the visible fields. For example, if calculating force, input charges and distance.

Step 3: Choose the Medium

Select the medium between the charges:

Vacuum/Air (default $k = 8.99 \times 10^9$ k=8.99×109)
Water
Glass
Paper

The calculator adjusts $k$ k automatically based on your selection.

Step 4: Click Calculate

The tool computes your result and displays:

The calculated value with scientific notation
The other related variables
The Coulomb constant used
The nature of force (Attractive or Repulsive)

Step 5: Reset if Needed

Use the Reset button to clear inputs and start over.

Example Calculation

Problem: Calculate the force between two charges of $5 \times 10^{-6} \, C$ 5×10−6C and $-3 \times 10^{-6} \, C$ −3×10−6C separated by 0.02 meters in air.

Steps:

Select Calculate Force (F).
Enter Charge 1 = $5 \times 10^{-6}$ 5×10−6 C
Enter Charge 2 = $-3 \times 10^{-6}$ −3×10−6 C
Enter Distance = 0.02 m
Select Medium = Vacuum / Air
Click Calculate.

Result:
Force $F \approx 3.37 \times 10^{-1}$ F≈3.37×10−1 Newtons (attractive force because charges are opposite signs).

Why Use This Coulomb Calculator?

Accurate calculations: Reduces manual errors and simplifies complex math.
Multiple calculation options: Find force, any charge, or distance easily.
Medium selection: Adjusts constant for realistic scenarios.
Scientific notation: Displays results clearly for very large or small values.
Instant feedback: Fast, user-friendly interface saves time.
Educational: Helps students understand electrostatics concepts better.

Important Concepts Explained

Force Type: Attractive or Repulsive

Attractive force occurs when charges have opposite signs (positive and negative).
Repulsive force occurs when charges have the same sign (both positive or both negative).

Medium and Coulomb Constant

The constant $k$ k decreases in materials with higher permittivity. For example:

Vacuum/Air: $8.99 \times 10^9$ 8.99×109 N·m²/C²
Water: Approx. $1.12 \times 10^8$ 1.12×108 N·m²/C² (due to water’s high permittivity)
Glass and Paper have intermediate values.

This affects the strength of the force.

Units

Force in Newtons (N)
Charge in Coulombs (C)
Distance in meters (m)

Make sure your inputs use these units for accurate results.

15 Frequently Asked Questions (FAQs)

1. What is Coulomb’s Law?
It quantifies the electrostatic force between two point charges as proportional to the product of the charges and inversely proportional to the square of the distance.

2. Can this calculator find any unknown in Coulomb’s formula?
Yes, it can calculate force, charge 1, charge 2, or distance given the others.

3. Why does the Coulomb constant change with the medium?
Because the electric permittivity of the medium influences the force between charges.

4. What if I input zero distance?
The calculator will alert you since distance cannot be zero (division by zero error).

5. Can charges be negative?
Yes, charges can be positive or negative; the calculator considers their absolute values for force magnitude.

6. How is force direction determined?
Force is attractive if charges are opposite; repulsive if charges are the same sign.

7. What units should I use?
Force in Newtons, charge in Coulombs, distance in meters.

8. Can I use this for real-world materials?
Yes, choose the correct medium to approximate real-world permittivity.

9. Is the calculator valid for point charges only?
Yes, Coulomb’s Law applies to point or spherically symmetric charges.

10. Why is scientific notation used?
Because charges and forces often involve very large or small numbers.

11. Can I calculate charge if I know force, distance, and the other charge?
Yes, select the correct calculation type and input the known values.

12. What happens if I leave input fields blank?
The calculator will alert you to enter valid numbers.

13. Can the calculator handle decimal inputs?
Yes, it supports decimal and exponential notation.

14. Does the calculator show the nature of force?
Yes, it indicates if the force is attractive or repulsive.

15. Can this be used for education or homework?
Absolutely! It’s designed for students and educators to simplify learning.

Conclusion

The Coulomb Calculator is an essential tool for anyone dealing with electric charges and forces. It removes the hassle of manual calculations, adjusts for real-world conditions, and helps you understand the physics behind electrostatic interactions. Use this calculator to quickly solve problems, verify homework, or conduct experiments with confidence.

Try it today and make electrostatics easier than ever!