Ampere's Law Calculator

Ampere's Law states that the magnetic field created around a current-carrying conductor is directly proportional to the current flowing through it. For an infinitely long straight wire, the magnetic field forms concentric circles around the wire and decreases with distance.

For a straight current-carrying wire, use the formula B = (μ₀ × I) / (2π × r), where B is magnetic field, μ₀ is permeability of free space (4π × 10⁻⁷ H/m), I is current in amperes, and r is distance from the wire in meters.

Tesla (T) and Gauss (G) are both units of magnetic field strength. 1 Tesla equals 10,000 Gauss. Tesla is the SI unit and is commonly used in scientific applications, while Gauss is often used for smaller magnetic fields like Earth's magnetic field (about 0.5 G).

The permeability of free space (μ₀) is a fundamental physical constant equal to 4π × 10⁻⁷ H/m (henries per meter). It represents the ability of a vacuum to support the formation of a magnetic field and is used in Ampere's Law calculations.

Magnetic field strength decreases inversely with distance from the current-carrying wire. If you double the distance, the magnetic field becomes half as strong. This relationship follows the 1/r pattern in the Ampere's Law formula.

Ampere's Law applies to any current distribution, but the simple formula B = (μ₀ × I) / (2π × r) is specifically for an infinitely long straight wire. For other shapes like loops or coils, more complex mathematical analysis is required.

Earth's magnetic field is about 0.5 Gauss (50 μT). A refrigerator magnet produces about 100 Gauss (0.01 T). MRI machines use fields of 1-3 Tesla. Current-carrying household wires typically create fields of microTesla to milliTesla at close distances.

The right-hand rule determines the direction of the magnetic field around a current-carrying wire. Point your right thumb in the direction of current flow, and your fingers curl in the direction of the magnetic field lines around the wire.