Magnetic Field Calculator Formula
Understand the math behind the magnetic field calculator. Each variable explained with a worked example.
Formulas Used
Magnetic Field
magnetic_field = 4e-7 * pi * current / (2 * pi * distance)Magnetic Field (μT)
magnetic_field_ut = 4e-7 * pi * current / (2 * pi * distance) * 1e6Variables
| Variable | Description | Default |
|---|---|---|
current | Current(A) | 10 |
distance | Distance from Wire(m) | 0.05 |
How It Works
Magnetic Field of a Straight Wire
A current-carrying wire generates a circular magnetic field around it.
Formula
B = mu_0 * I / (2 * pi * r)
where mu_0 = 4*pi x 10^-7 T·m/A is the permeability of free space. The field direction follows the right-hand rule.
Worked Example
Magnetic field 5 cm from a wire carrying 10 A.
- 01B = mu_0 * I / (2*pi*r)
- 02B = 4*pi*1e-7 * 10 / (2*pi*0.05)
- 03B = 4e-6 / 0.1
- 04B = 4e-5 T = 40 μT
Frequently Asked Questions
What is the right-hand rule?
Point your right thumb in the direction of current flow. Your curled fingers show the direction of the circular magnetic field.
What is the permeability of free space?
mu_0 = 4*pi x 10^-7 T·m/A, a fundamental constant that characterizes the strength of magnetic interactions in vacuum.
How strong is Earth's magnetic field?
About 25 to 65 μT at the surface, depending on location. It is relatively weak compared to permanent magnets.
Ready to run the numbers?
Open Magnetic Field Calculator