Moving Charges and Magnetism - Vocabulary Flashcards (Video Notes)

Key vocabulary terms and definitions from the lecture notes on moving charges and magnetism, covering magnetic fields, forces, devices, and conversion formulas.

Magnetic Field

A vector field around magnets and current-carrying conductors where magnetic effects can be observed; direction aligns with the force on moving charges.

Tesla (T)

SI unit of magnetic flux density; 1 T = 1 Weber per square meter (Wb/m^2); equals 10^4 Gauss.

Gauss (G)

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

Biot–Savart Law

Describes the magnetic field from a current element dl: dB = (μ0/4π) I dl × r̂ / r^2; integrated over the current gives B.

Ampere's Circuital Law

The line integral of the magnetic field around a closed loop equals μ0 times the current through the loop: ∮ B · dl = μ0 I_enclosed.

Lorentz Force

Force on a charged particle q moving with velocity v in a magnetic field B: F = q v × B.

Magnetic Dipole Moment

For a current loop, M = N I A (N = number of turns, I = current, A = loop area); vector along the loop’s normal.

Solenoid

A hollow tube wound with many turns of insulated wire; inside, it produces a nearly uniform magnetic field: B = μ0 n I (n = turns per unit length).

Magnetic Field Inside a Solenoid

Inside a long solenoid, the magnetic field is uniform and given by B = μ0 n I.

Magnetic Field Due to a Straight Wire

Field at distance r from a long straight current-carrying wire: B = μ0 I /(2π r); direction is tangential (use right-hand rule).

Right-Hand Rule

Rule to determine B direction around a current: point thumb along current; fingers curl in the direction of B.

Permeability of Free Space (μ0)

Constant μ0 = 4π × 10^-7 T·m/A; relates B and H in vacuum (B = μ0 H).

Moving Charged Particle in Magnetic Field

A moving charge experiences F = q v × B; if v ⟂ B, the path is circular with radius r = m v /(q B).

Current-Carrying Conductor in Magnetic Field

Force on a straight wire of length l carrying current I in a magnetic field B: F = I l × B; magnitude F = I l B sin θ.

Ammeter

Instrument to measure current; ideal ammeter has zero resistance and is connected in series.

Voltmeter

Instrument to measure potential difference; ideal voltmeter has infinite resistance and is connected in parallel.

Galvanometer

A coil-based instrument that deflects in proportion to current; the basis for galvanometers used in ammeters and voltmeters.

Conversion: Galvanometer to Ammeter

Add a shunt resistor in parallel with the galvanometer so most current bypasses it; Rs = Rg · Igfs /(Itotal − Igfs) = Rg · Ifs /(Itotal − Ifs).

Conversion: Galvanometer to Voltmeter

Connect a resistor in series with the galvanometer to extend voltage range; Vfs = Igs (Rg + Rseries); thus Rseries = Vfs / Igs − Rg.