C30 - Sources of the Magnetic Field

Biot-Savart Law

permeability of free space constant

μ₀ = 4π • 10^-7 (T • m)/A

magnetic field induced by a current-carrying wire

• infinite line: μ₀I/2πa

• finite line: (μ₀I/4πa)(sinθ₁ - sinθ₂)

• circle: μ₀I/2a

• arc: (μ₀I/4πa)(θ)

magnetic field on axis of circular current loop

magnetic force (between two wires carrying currents)

• same current attracts

• opposite current repels

Ampere’s Law

• current enclosed by some closed path is proportional to magnetic field strength

• magnetic field induced by the current

magnetic field inside a solenoid

magnetic flux

Φ = ABcosθ

Gauss’s Law (magnetism)

ferromagnetic

permanent magnetism

paramagnetic

weak magnetism induced by an external magnetic field

diamagnetic

magnetic force acting opposite to the applied field

orbital magnetic moment of an atom

• angular momentum & magnetic moment point in opposite directions (for electrons)

Curie temperature

temperature limit above which ferromagnetic materials break down