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Electricity & Magnetism
Electricity & Magnetism

Magnetic Field (Long Wire)

B=μ0I2πrB = \frac{\mu_0 I}{2\pi r}

Magnetic field around long straight wire.

Variables

B
Magnetic field
Field strength
T
μ₀
Permeability
4π×10⁻⁷
H/m
I
Current
Current in wire
A
r
Distance
From wire
m

Derivation

From Biot-Savart law or Ampere's law.

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Common questions

What is the Magnetic Field (Long Wire) formula?

Magnetic Field (Long Wire) is written B = μ₀ I/2πr. Magnetic field around long straight wire. It belongs to Electricity & Magnetism, under Magnetism.

What are the units in B = μ₀ I/2πr?

In SI units, B is magnetic field, measured in kg/(A·s²); μ₀ is permeability, measured in kg·m/(A²·s²); I is current, measured in A; r is distance, measured in m.

How is the Magnetic Field (Long Wire) formula derived?

From Biot-Savart law or Ampere's law. The result is B = μ₀ I/2πr.