Glossary of Key Terms¶
Definitions of the recurring physical concepts used across the 18 experiments and 7 workshops in this guide, in alphabetical order. Each entry links back to the experiment(s) where the term is most central.
A¶
Ampere's circuital law — \(\oint \vec B\cdot d\vec l = \mu_0 I_{enc}\); used to find the field of highly symmetric current distributions. See Solenoid & Toroid.
Atomic/molecular polarizability (α) — The induced dipole moment per unit local electric field experienced by a single atom or molecule. See Dielectric Polarization.
B¶
Biot–Savart law — Gives the magnetic field contribution from an infinitesimal current element; the magnetostatic analogue of Coulomb's law. See Biot–Savart.
Bound charge — Charge that appears at the surface (or within the volume) of a polarized dielectric due to the alignment of its internal dipoles, as distinct from free charge. See Dielectric Polarization.
Brewster's angle (θ_B) — The angle of incidence at which p-polarized light is not reflected at all at a dielectric interface. See Reflection, Refraction & Brewster's Angle.
C¶
Clausius–Mossotti relation — Connects the macroscopic dielectric constant to the microscopic atomic polarizability, including the local-field correction. See Dielectric Polarization.
Coercivity (H_c) — The reverse magnetizing field required to bring the flux density of a magnetized material back to zero. See Magnetic Hysteresis.
Coulomb's law — The force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation. See Coulomb's Law.
D¶
Dielectric constant (ε_r) — The relative permittivity of a material; the factor by which it increases a capacitor's capacitance relative to vacuum. See Parallel-Plate Capacitor.
Dipole moment (p) — A vector p = q·(2a) characterising the strength and orientation of an electric dipole. See Electric Dipole.
E¶
Eddy current — A circulating induced current set up in a bulk conductor by a changing magnetic flux, used constructively in eddy-current testing and braking, and minimised in transformer cores. See WS4: Eddy-Current NDT.
F¶
Faraday's law — The EMF induced in a circuit equals the negative rate of change of magnetic flux linkage through it. See Faraday's Law.
G¶
Gauss's law — The net electric flux through any closed surface equals the enclosed charge divided by ε₀. See Gauss's Law.
H¶
Helmholtz coils — A pair of identical coaxial coils separated by a distance equal to their radius, producing a highly uniform field at their common centre. See Circular Coil & Helmholtz Coils.
Hysteresis loop — The closed B–H curve traced by a ferromagnetic material as the applied field is cycled; its enclosed area equals the energy dissipated per cycle. See Magnetic Hysteresis.
L¶
Lenz's law — The induced current always flows in the direction that opposes the change in flux producing it. See Faraday's Law and Motional EMF.
M¶
Maxwell's equations — The four coupled equations (Gauss's law for E, Gauss's law for B, Faraday's law, Ampere–Maxwell law) that fully describe classical electromagnetism and predict electromagnetic waves. See Maxwell's Equations & Plane Waves.
Motional EMF — The EMF generated in a conductor moving through a magnetic field, ε = BLv for a rod on rails. See Motional EMF.
Q¶
Quality factor (Q) — A dimensionless measure of the sharpness of an LCR circuit's resonance, Q = ω₀L/R. See LCR Resonance.
R¶
Retentivity / Remanence (B_r) — The flux density remaining in a ferromagnetic material after the applied field is removed. See Magnetic Hysteresis.
S¶
Skin depth (δ) — The depth in a conductor at which an EM wave's amplitude falls to 1/e of its surface value. See Skin Depth.
T¶
Time constant (τ) — The characteristic time scale of an RC or RL transient (τ = RC or τ = L/R) at which the exponential response reaches (1 − 1/e) of its final change. See RC/RL Transients.
V¶
VSWR (Voltage Standing-Wave Ratio) — A measure of impedance mismatch on a transmission line; VSWR = 1 for a perfectly matched load. See WS7: RF Impedance Matching.