Magnetism & Electromagnetism - Video Notes Vocabulary Flashcards

Vocabulary-style flashcards covering essential concepts, laws, and definitions from the provided magnetism/electromagnetism notes.

Electric field

A region around a charge where another charge experiences electrostatic force; produced by charges at rest.

Magnetic field (B)

Vector field around magnets and currents that exerts magnetic forces on moving charges; measured in Tesla.

Electromagnetic wave

Self-propagating oscillation of changing electric and magnetic fields, emitted by accelerating charges.

Oersted's experiment

Found that electric current in a wire produces a magnetic field, demonstrated by deflection of a compass needle.

Biot–Savart law

Gives the magnetic field from a current element: dB = (μ0/4π) (I dl × r̂)/r^2.

Ampere's law

Line integral of B around a closed loop equals μ0 times the enclosed current: ∮B·dl = μ0 I_enclosed.

Permeability of free space (μ0)

Magnetic constant; μ0 = 4π×10^-7 N/A^2.

Magnetic dipole moment (μ)

Moment of a current loop: μ = N I A; direction given by the right-hand rule.

Magnetic field due to a straight wire

B = μ0 I /(2π r); circular field around the wire.

Magnetic field at the center of a circular loop

B_center = μ0 I /(2R) for a single loop; B = μ0 N I /(2R) for N turns.

Magnetic field on the axis of a circular loop

B(z) = μ0 I R^2 / [2(R^2 + z^2)^(3/2)].

Toroidal magnetic field

Inside a toroid: B = μ0 N I /(2π r) (mean radius r).

Lorentz force

Force on a moving charge: F = q(v × B); magnitude F = q v B sinθ.

Velocity selector

Device using E and B so that q(E + v×B) = 0; for perpendicular fields, v = E/B.

Force on a current-carrying conductor

F = I L × B; magnitude F = I L B sinθ; direction by Fleming's left-hand rule.

Torque on a current loop

τ = N I A B sinφ; equivalently τ = μ × B with μ = N I A.

Moving coil galvanometer

Sensitive current meter with a coil in a magnetic field and restoring spring.

Shunt resistor

resistor placed in parallel with a galvanometer to extend the ammeter range.

Ammeter

Instrument to measure current; galvanometer plus shunt converts to ammeter.

Voltmeter

Instrument to measure voltage; galvanometer with series resistor extends voltage range.

Ampere (definition)

The current that would produce a force of 2×10^-7 N per meter between two parallel conductors 1 m apart.

Force between parallel wires

F/L = μ0 I1 I2 /(2π d); attraction when currents are in the same direction.

Magnetic dipole moment (restate)

μ = N I A for a current loop; determines orientation in an external magnetic field.

Magnetic field lines

Invisible lines representing B; originate at North, end at South; inside magnets go from South to North; form closed loops.

Gauss's law for magnetism

Net magnetic flux through any closed surface is zero: ∮ B·dA = 0.

Magnetic permeability (μ)

Material property μ = μ0 μr; measures how well a material supports magnetic flux.

Relative permeability (μr)

Ratio μ/μ0; dimensionless; μr > 1 for most magnetic materials except some diamagnets.

Magnetic intensity (H)

Magnetizing field strength; B = μ0(H + M) and H = B/μ0 − M.

Magnetization (M)

Net magnetic moment per unit volume; M = χm H for linear materials.

Magnetic susceptibility (χm)

Ratio M/H; positive for paramagnetic/ferromagnetic, negative for diamagnetic.

Diamagnetic materials

Weakly repelled by magnetic fields; χm < 0; μr < 1; examples: bismuth, copper, lead.

Paramagnetic materials

Weakly attracted to magnetic fields; χm > 0; μr > 1; examples: Al, Na, Ca; temperature dependent.

Ferromagnetic materials

Strongly magnetized by external fields; μr ≫ 1; examples: Fe, Ni, Co; temperature dependent.

Curie's Law

For paramagnets, χ ∝ 1/T; M = χ H and χ = C/T; Curie constant C.

Bar magnet

A magnet with a North and a South pole; commonly made of Fe/Ni/Co; field lines from N to S.

Solenoid as magnet

A coil that acts like a bar magnet with distinct poles; inside field B = μ0 n I.

Pole strength

A measure of the strength of magnetic poles; part of classical magnetism concepts.

Magnetic dipole moment orientation

Direction of μ follows the right-hand rule relative to current; defines pole orientation.