Enter the permeability of free space, current, and distance from the wire into the calculator to determine the magnetic field. This calculator can also evaluate any of the variables given the others are known.

Ampere’s Law Formula

The following formula is used to calculate the magnetic field using Ampere’s Law. 

B = (μ0 * I) / (2 * π * r)

Variables:

  • B is the magnetic field (Tesla) μ0 is the permeability of free space (4π x 10^-7 T m/A) I is the current (Amperes) r is the distance from the wire (meters)

To calculate the magnetic field using Ampere’s Law, multiply the permeability of free space by the current. Then divide the result by the product of 2, pi, and the distance from the wire.

What is Ampere’s Law?

Ampere’s Law is a fundamental principle in electromagnetism that relates the circulating magnetic field in a closed loop to the electric current passing through the loop. Named after its discoverer, French physicist André-Marie Ampère, the law states that the integral of the magnetic field around a closed loop is equal to the product of the permeability of free space and the current enclosed by the loop. This law is used in the study of electric circuits, magnetic fields, and is one of Maxwell’s four equations which form the basis of classical electrodynamics.

How to Calculate Ampere’S Law?

The following steps outline how to calculate the magnetic field using Ampere’s Law.

  1. First, determine the values of the variables:
  2. Next, substitute the values into the formula: B = (μ0 * I) / (2 * π * r)
  3. Finally, calculate the magnetic field (B) using the formula.
  4. After inserting the variables and calculating the result, check your answer with the calculator above.

    5. Example Problem:

    Use the following variables as an example problem to test your knowledge.

    magnetic field (B) = ?

    permeability of free space (μ0) = 4π x 10^-7 T m/A

    current (I) = 2 Amperes

    distance from the wire (r) = 0.5 meter