Magnetism and Inductors - Vocabulary Flashcards

Vocabulary flashcards covering key concepts from the Magnetism and Inductors lecture notes.

Intrinsic magnetism

Magnetism arising from the intrinsic spin of elementary particles (e.g., electrons) which produces a magnetic dipole moment.

Magnetic dipole moment (spin)

Magnetic moment produced by the intrinsic spin of particles such as electrons.

Orbital magnetic dipole moment

Magnetic moment produced by the orbital motion of electrons around a nucleus.

Vector sum of magnetic dipole moments

The overall magnetic property of a material results from the vector addition of many individual magnetic dipole moments.

Ferromagnetism

Phenomenon where certain materials (e.g., Fe, Co, Ni) form permanent magnets due to aligned magnetic domains.

Magnetic domains

Regions within a magnetic material where magnetic moments are aligned; their alignment determines overall magnetization.

Unpaired electron spins

Unpaired spins contribute to magnetism; their alignment leads to ferromagnetism.

North pole

One end of a magnet from which magnetic field lines emerge.

South pole

The opposite end of a magnet to which magnetic field lines converge.

Like poles repel

Poles with the same polarity push away from each other.

Unlike poles attract

Poles with opposite polarity pull toward each other.

Magnetic flux (Φ)

Total magnetic flux passing through a surface; measured in Webers (Wb).

Magnetic flux density (B)

Magnetic field strength; measured in Teslas (T); symbol B.

Permeability (μ)

Material’s ability to support the formation of a magnetic field (μ0 for free space).

Absolute permeability

Permeability of a material (often denoted μ), the ability to pass magnetic flux through the material.

μ0 (permeability of free space)

Magnetic permeability of vacuum: μ0 = 4π×10−7 H/m.

Relative permeability (μr)

Ratio of a material’s permeability to μ0: μr = μ/μ0.

Magnetic field strength (H)

MMF per unit length; measured in A/m; related to MMF and geometry.

Magnetomotive force (MMF)

Force that drives magnetic flux, F = NI (current I through N turns).

Ampere-turns

Unit of MMF, product of current and number of turns.

Reluctance (S)

Opposition to magnetic flux; S = l/(μA) for a uniform core.

Right-hand grip rule

Rule to determine the direction of magnetic field around a current-carrying conductor.

Faraday’s law of induction

EMF is induced in a conductor when the magnetic flux through it changes over time.

Lenz’s law

The direction of the induced EMF (and current) is such that it opposes the change in flux.

Electromagnetic induction

Phenomenon of generating EMF by changing magnetic flux or through movement in a magnetic field.

Induced EMF (E)

Voltage generated due to electromagnetic induction.

Fleming’s right-hand rule

Rule for motion-induced EMF: thumb (motion), index (field), middle (current).

Self-inductance

EMF induced in a circuit by its own changing current/flux; L is the inductance.

Inductance (Henrys, H)

Property of a circuit that relates E to dI/dt; unit is the Henry.

Mutual inductance

EMF induced in one coil due to changing current in a nearby coil; symbol M.

Coefficient of coupling (K)

Ratio describing how effectively flux from one coil links the other; M = K√(L1L2).

Air-core inductor

Inductor with no ferromagnetic core; linear B–H characteristics but low inductance.

Ferromagnetic core inductor

Inductor using a ferromagnetic core to achieve high inductance; B–H non-linear.

Saturation

Point where a magnetic material cannot be magnetized further; non-linear region of B–H curve.

Remanent flux density (Br)

Residual magnetization present when the external field is removed (H = 0).

Coercive force (Hc)

Field strength required to reduce magnetization to zero.

Hysteresis loop

Plot of B versus H showing history-dependent magnetization; area relates to energy loss.

Hysteresis loss

Energy wasted in reversing magnetization per cycle; proportional to loop area and frequency.

Soft magnetic materials

High permeability, low coercivity; easy to magnetize/demagnetize; low hysteresis loss.

Hard magnetic materials

High coercivity; retain magnetization; used for permanent magnets; higher hysteresis loss.

Eddy current loss

Energy loss from circulating currents in a conductor's core; reduced by laminations.

Laminations

Thin insulated layers in a core to suppress eddy currents.

Retentivity (retentive magnetization)

Ability to remain magnetized after the external field is removed.

Magnetic shielding

Use of high-permeability materials to divert magnetic flux away from sensitive areas.

Degaussing

Process of demagnetizing by applying a decreasing, alternating magnetic field.

Magnetometer

Device used to detect and measure magnetic fields or locate stray magnetism.

Electromagnet

Magnet produced by passing current through a coil around a ferromagnetic core; field ceases when current stops.

E = Blv (motional EMF)

EMF induced in a moving conductor of length l, moving at velocity v in a magnetic field B.