Magnetic dipoles have magnetic force lines {magnetic field}| {flux density} {magnetic intensity} {magnetic induction}, from south pole to north pole. Magnetic field H is magnetic force F divided by pole strength p: H = F/p.
wire
Around wires, magnetic field H is space magnetic permeability k' times current I divided by two times pi times distance d from wire: H = (k' * I) / (2 * pi * d). Around solenoids, magnetic field H is space magnetic permeability k' times wire-turn number n times current I: H = k' * n * I. Around toroids, magnetic field H is space magnetic permeability k' times wire-turn number n times current I divided by two times pi times toroid radius r: H = (k' * n * I) / (2 * pi * r).
direction
Positive current in thumb direction makes magnetic field that circles conductor in right-hand finger direction {right hand rule, magnetic field}.
Numbers {magnetic flux}| of magnetic-field lines go through areas.
Magnetic field B times distance ds charge moves in field equals field magnetic permeability µ times current I {Ampere's circuital law} {Ampere circuital law} {Ampere's law}: integral of B * ds = µ * I. Current flows inside path of distance.
Because relativistic effects have small energies, atoms have quantized electric and magnetic fields. Magnetism quantum {Bohr magneton} is small magnetic pole.
Magnetic field relates to magnetic flux {Biot-Savart law}.
Energy conservation causes voltage from electromagnetic induction to make magnetic field opposed to original magnetic field {Lenz law}.
5-Physics-Electromagnetism-Magnetism
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Date Modified: 2022.0225