| Term | Definition | Unit / Dimensional Formula |
|---|---|---|
| **Magnetic Field (B)** | The region around a magnet or current where magnetic forces act; defined by force on a moving charge F = qv×B | Tesla (T); [$MT^{-2}$$A^{-1}$] |
| **Biot-Savart Law** | dB = (μ_{0}/4π)(I dl sinθ/$r^{2}$); gives magnetic field due to a current element; magnetic analog of Coulomb's law | [$MT^{-2}$$A^{-1}$] |
| **Ampere's Circuital Law** | ∮B·dl = μ_{0}I_enc; line integral of B around any closed loop equals μ_{0} × enclosed current | [M$LT^{-2}$$A^{-1}$] |
| **Permeability of Free Space (μ_{0})** | 4π × 10^{-7} T·m/A; fundamental constant relating B to the current producing it | [M$LT^{-2}$$A^{-2}$] |
| **Lorentz Force** | F = q(E + v×B); total electromagnetic force on a charge q moving with velocity v | Newton (N); [M$LT^{-2}$] |
| **Magnetic Moment (M)** | M = NIA for a current loop; measure of loop's tendency to align with an external field | A·$m^{2}$; [$AL^{2}$] |
| **Torque on a Current Loop** | τ = NIAB sinθ = MB sinθ; torque experienced by a magnetic moment in an external field | N·m; [$ML^{2}$$T^{-2}$] |
| **Solenoid** | A long cylindrical coil with N turns and length L; creates uniform B = μ_{0}nI inside | — |
| **Toroid** | A donut-shaped solenoid; B = μ_{0}NI/(2πr) inside ring; B = 0 in hollow centre and outside | — |
| **Cyclotron Radius** | r = mv/(qB); radius of circular path of a charged particle in uniform B | m; [L] |
| **Cyclotron Period** | T = 2πm/(qB); time for one complete revolution; independent of speed | s; [T] |
| **Magnetic Susceptibility (χ)** | χ = M/H; dimensionless measure of how much a material magnetises in response to H | Dimensionless |
| **Relative Permeability (μᵣ)** | μᵣ = 1 + χ; ratio of material's permeability to μ_{0}; dimensionless | Dimensionless |
| **Diamagnetism** | χ < 0; material is weakly repelled by external field; examples: Cu, Bi, $H_{2}O$ | — |
| **Paramagnetism** | 0 < χ << 1; material weakly attracted; obeys Curie's law χ = C/T | — |
| **Ferromagnetism** | χ >> 1; strongly attracted; has magnetic domains; shows hysteresis | — |
| **Retentivity** | Residual magnetic flux density (B) retained when external field H is reduced to zero | Tesla (T) |
| **Coercivity** | Magnitude of reverse H required to reduce residual B to zero; [A/m] | A/m; [$L^{-1}$A] |$
Part of MAG-01 — Magnetic Effects of Current & Magnetism
Definitions Glossary — 18 Key Terms
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