Electromagnetism & Electronics — 11 Terms Defined

Magnetic Dipole Electromagnetism & Electronics A·m² (or J/T) The basic magnetic structure created by a closed circulating current loop or intrinsic particle spin, possessing North and South magnetic poles. μ = I A, τ = μ × B

Magnetic Dipole Moment Electromagnetism & Electronics A·m² (or J/T) A vector quantity determining the torque experienced by a magnetic dipole when placed in an external magnetic field. μ = I A, U = -μ · B

Magnetic Field Electromagnetism & Electronics T (Tesla = N/(A·m)) A vector field generated by moving electric charges, electric currents, or intrinsic magnetic moments that exerts magnetic forces on other moving charges and dipoles. F_mag = q (v × B), B = μ₀ I / (2π r)

Magnetic Flux Electromagnetism & Electronics Wb (Webers = T·m²) The measure of the total magnetic field passing normally through a specified surface area. Φ_B = ∫ B · dA = |B| |A| cos θ

Magnetic Hysteresis Electromagnetism & Electronics J/m³ (Joules per cubic meter) The lagging of magnetization behind the applied magnetizing field in ferromagnetic materials during cyclic magnetization. Hysteresis Loss Area = ∫ H dB

Magnetic Permeability Electromagnetism & Electronics H/m (or T·m/A) A material property measuring the degree to which a medium supports and concentrates magnetic flux inside itself when subjected to a magnetic field. μ = B / H = μ_r μ₀, μ₀ = 4π × 10⁻⁷ T·m/A

Magnetic Susceptibility Electromagnetism & Electronics Dimensionless A dimensionless material property measuring the degree of magnetization induced in a material per unit applied magnetic field strength. M = χ_m H, μ_r = 1 + χ_m

Maxwell's Equations Electromagnetism & Electronics Various SI Units The set of four fundamental partial differential equations that unify electricity, magnetism, and optics into classical electrodynamics. ∇·E = ρ/ε₀, ∇·B = 0, ∇×E = -∂B/∂t, ∇×B = μ₀J + μ₀ε₀∂E/∂t

MOSFET Electromagnetism & Electronics A (Current) A Metal-Oxide-Semiconductor Field-Effect Transistor that uses an insulated gate voltage to control current flow through an underlying semiconductor channel. I_D = ½ μ_n C_ox (W/L) (V_GS - V_th)²

Moving Coil Galvanometer, Ammeter & Voltmeter Electromagnetism & Electronics A (Current), V (Voltage) An electromechanical instrument that measures small currents using magnetic torque on a pivoted coil, converted to an ammeter or voltmeter using shunts or series resistors. τ = N I A B = k θ; Ammeter: S = I_g G / (I - I_g); Voltmeter: R_s = (V / I_g) - G

Mutual Inductance Electromagnetism & Electronics H (Henries) The induction of an electromotive force in a secondary circuit loop caused by a time-varying current in an adjacent primary circuit loop. E₂ = -M (dI₁/dt), M = k √(L₁ L₂)