Magnetic Field Calculator
Solenoid
Calculate the magnetic field inside an ideal solenoid (B = μ₀nI)
Straight Wire
Calculate the magnetic field at distance r from a long straight current-carrying wire
Circular Loop (on axis)
Calculate the magnetic field along the axis of a circular current loop
Formula
Solenoid: B = μ₀nI | Wire: B = μ₀I/(2πr) | Loop: B = μ₀IR²/(2(R²+x²)^(3/2)) | μ₀ = 4π×10⁻⁷ T·m/A
Frequently Asked Questions
How do you calculate the magnetic field of a solenoid?
For an ideal solenoid: B = μ₀nI, where n = N/L is the turn density (turns per meter), I is the current, and μ₀ = 4π×10⁻⁷ T·m/A. The field is uniform inside and nearly zero outside. A 1000-turn, 0.5m solenoid with 1A produces B ≈ 2.51 mT.
What is the Biot-Savart law?
The Biot-Savart law gives the magnetic field dB from a small current element: dB = (μ₀/4π)(Idl × r̂)/r². For a long straight wire, integration gives B = μ₀I/(2πr). For a circular loop at center: B = μ₀I/(2R).
How strong is Earth's magnetic field?
Earth's magnetic field is approximately 25-65 μT (0.25-0.65 Gauss) at the surface. For comparison, a refrigerator magnet is about 5 mT, an MRI machine is 1.5-3 T, and a neodymium magnet is about 1.4 T.
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