Magnetism and Electromagnetic Induction Glossary

The line integral of $\vec{B}$ around a closed loop equals $\mu_0$ times the enclosed current: $\oint \vec{B} \cdot d\vec{l} = \mu_0 I_{\text{enc}}$.

Maxwell's addition to Ampere's law: a changing electric field acts as a source of magnetic field, even without physical current. Completes Maxwell's equations.

The process by which a changing magnetic flux induces an EMF and current in a conductor. Discovered by Faraday and Henry independently.

A self-sustaining oscillation of electric and magnetic fields propagating at the speed of light. Includes radio, microwave, infrared, visible, UV, X-ray, and gamma radiation.

A changing magnetic flux induces an EMF: $\varepsilon = -N d\Phi_B/dt$. The basis of electric generators and transformers.

The direction of induced current opposes the change in flux that produced it. Encodes conservation of energy in electromagnetic induction.

A vector field that exerts a force on moving charges and current-carrying conductors. Symbol: $\vec{B}$. SI unit: tesla (T).

The integral of the magnetic field over a surface: $\Phi_B = \int \vec{B} \cdot d\vec{A}$. For uniform fields: $\Phi_B = BA\cos\theta$. SI unit: weber (Wb).

The four fundamental equations governing all classical electromagnetic phenomena: Gauss's laws for E and B, Faraday's law, and the Ampere-Maxwell law.

The constant $\mu_0 = 4\pi \times 10^{-7}$ T m/A that appears in magnetic field formulas. It quantifies the strength of magnetic interactions in vacuum.

A mnemonic for finding the direction of magnetic forces, fields, and induced currents. Point thumb along current or velocity, curl fingers in field direction.

A helical coil of wire that produces a nearly uniform magnetic field inside: $B = \mu_0 nI$.

A device that changes AC voltage levels using electromagnetic induction between two coils (primary and secondary) sharing a magnetic core.