Electromagnetism & Electromagnetic Induction – Vocabulary Review

A comprehensive set of vocabulary flashcards summarizing key definitions, rules, units, and equations from the electromagnetism and electromagnetic induction lecture notes.

Magnetic Field (B)

A vector region around a magnet or current-carrying conductor where magnetic forces are experienced.

Magnetic Flux (Φ)

The product of magnetic flux density and the perpendicular area it penetrates (Φ = B·A cos θ), measured in Weber (Wb).

Magnetic Flux Density

Another name for magnetic induction; it quantifies magnetic field strength per unit area and is measured in Tesla (T).

Weber (Wb)

SI unit of magnetic flux; 1 Wb = 10⁸ Maxwells or 1 T·m².

Maxwell

CGS unit of magnetic flux; 10⁸ Maxwells equal 1 Weber.

Tesla (T)

SI unit of magnetic flux density; 1 T = 1 N A⁻¹ m⁻¹.

Gauss (G)

CGS unit of magnetic flux density; 1 G = 10⁻⁴ T.

Ampere’s Law

Relates integrated magnetic field around a closed loop to the current it encloses; magnetic analogue of Gauss’s law.

Cyclotron Frequency

Frequency qB/2πm used to accelerate positive charges in a cyclotron.

Right-Hand Rule (Straight Wire)

Thumb points with current; curled fingers show the circular magnetic-field direction.

Fleming’s Left-Hand Rule

Gives force direction on a current-carrying conductor for conventional current (positive charges).

Fleming’s Right-Hand Rule

Gives direction of induced emf or force for electronic current (negative charges).

Palm Right-Hand Rule

Alternate rule for finding force on positive charges in a magnetic field using the right palm.

Palm Left-Hand Rule

Alternate rule for finding force on negative charges in a magnetic field using the left palm.

Force on Current-Carrying Conductor

F = B I L sin θ; magnetic force depends on field, current, length, and angle.

Force on Moving Charge

F = q v B sin θ; always perpendicular to both velocity and magnetic field.

Magnetic Force per Unit Length

For a wire, F/L = B I.

Earth’s Magnetic Field Strength

Approximately 0.5 Gauss (5 × 10⁻⁵ T).

Outside-Magnet Field Direction

Magnetic field lines run from North to South pole outside a magnet.

Inside-Magnet Field Direction

Magnetic field lines run from South to North pole inside a magnet; field is conservative there.

Trajectory: Outside→Inside Field

A charged particle projected from outside into a magnetic field follows a parabolic path.

Trajectory: Inside→Outside Field

A charged particle leaving a magnetic field traces a circular (trajectory) path.

Positive Charge, B Into Page

Moves anti-clockwise in the plane.

Negative Charge, B Into Page

Moves clockwise in the plane.

q/m Ratio Comparison

Electron has higher q/m than proton; proton has higher m/q than electron.

Alpha Particle Force

Experiences four times the magnetic force of a beta particle at same v and B (q v B with q = +2e, m heavier).

Equation I = Q v / L

Relates current to moving charge, its velocity, and conductor length.

Magnetic Flux at Specific Angles

Φ is max at 0°, zero at 90°, negative at 180° relative to surface normal.

Faraday’s Law

Induced emf (ε) in a coil equals negative rate of change of flux linkage: ε = −N ΔΦ/Δt.

Flux Linkage

Product of number of turns and magnetic flux (NΦ) threading a coil.

Lenz’s Law

Induced emf/current opposes the change producing it; consequence of energy conservation.

Self-Inductance (L)

Property of a coil to oppose change in its own current; ε = −L ΔI/Δt; unit Henry (H).

Mutual Inductance (M)

Voltage induced in one coil due to changing current in another; ε = −M ΔI/Δt.

Eddy Currents

Circular currents induced in bulk conductors that oppose motion or change in magnetic flux, causing resistive heating.

Transformer

Device that steps AC voltage up or down while keeping power (ideally) constant; works only with alternating current.

Step-Up Transformer

Secondary turns Ns > Primary turns Np; yields Vs > Vp and Is < Ip.

Step-Down Transformer

Secondary turns Ns < Primary turns Np; yields Vs < Vp and Is > Ip.

Transformer Equation

Vs/Vp = Ns/Np = Ip/Is (ideal case).

Transformer Frequency

Input and output frequencies are identical.

Transformer with DC Input

Produces no secondary voltage; Vs ≈ 0, since transformers require changing flux (AC).

AC Generator

Converts mechanical energy to electrical energy using Faraday’s law; emf varies sinusoidally.

Magnetic Induction Synonyms

Magnetic induction, magnetic flux density, and B-field all denote the same quantity.

1 Weber in Maxwells

1 Wb = 10⁸ Maxwells.

1 Gauss in Tesla

1 G = 10⁻⁴ Tesla.

Ampere’s Law for Solenoid

Magnetic field inside a long solenoid: B = μ₀ n I, where n = N/L.

Seismometer (Electromagnetic)

Earthquake-measuring device that uses electromagnetic induction; induced emf ∝ relative velocity, magnet strength, and coil turns.

Induced EMF vs Induced Current

Lenz’s law specifically gives the direction of induced current, not merely emf.

Right- vs Left-Hand Rule

Right hand applies to positive charges; left hand to negative charges for force direction.

Force Perpendicularity

Magnetic force on a moving charge is always perpendicular to both velocity and magnetic field.