IB Physics HL: Circuits, Simple Harmonic Motion (SHM) & Waves

Comprehensive vocabulary flashcards covering electric circuits, simple harmonic motion, wave mechanics, interference, diffraction, damping, and resonance for IB Physics HL.

Electric Circuit

A closed conduction loop that requires a source of potential difference (p.d.), connecting wires, and circuit components through which charge carriers can circulate.

Circuit Symbols

Standardized schematic diagrams representing electrical components including cells, batteries, switches, resistors, variable resistors, potentiometers, thermistors, LDRs, diodes, lamps, heating elements, motors, and earth ground connections.

Ammeter

A device connected in series within a circuit branch to measure electric current; an ideal ammeter has zero internal resistance ($R = 0$).

Voltmeter

A device connected in parallel across a circuit component to measure the potential difference between two points; an ideal voltmeter has infinite resistance ($R = \infty$).

Charge Carriers

Mobile charged particles whose flow constitutes an electric current; they are free (delocalised) electrons in metallic conductors and positive and negative ions in electrolytes.

Electric Current ($I$)

The rate of flow of electric charge carriers through a cross-section, defined as $I = \frac{\Delta q}{\Delta t}$ with unit ampere ($1\,\text{A} = 1\,\text{C}\,\text{s}^{-1}$); for $n$ particles each of charge $e$, $I = \frac{ne}{t}$.

Conventional Current vs. Electron Flow

Conventional current is defined as the flow of positive charge from the positive terminal to the negative terminal ($+\rightarrow -$), whereas electrons travel in the opposite direction from negative to positive ($-\rightarrow +$).

Drift Speed

The slow average net speed acquired by electrons moving opposite to an applied electric field through a conductor due to repeated collisions with vibrating lattice ions.

Direct Current (dc)

Electric current that flows in one direction only with a constant value, delivered by cells and batteries where the terminal polarity remains unchanging over time.

Potential Difference (p.d., $V$)

The work done per unit charge on moving a positive test charge between two points along the path of a current ($V = \frac{W}{q}$), measured in volts ($1\,\text{V} = 1\,\text{J}\,\text{C}^{-1}$).

Electronvolt ($\text{eV}$)

A unit of energy equal to the work required to move an electron through a potential difference of $1\,\text{V}$, calculated as $W = qV = (1.60 \times 10^{-19}\,\text{C})(1\,\text{V}) = 1.60 \times 10^{-19}\,\text{J}$.

Resistance ($R$)

The ratio of the potential difference across a conductor or component to the current flowing through it, defined by $R = \frac{V}{I}$ and measured in ohms ($\Omega$).

Resistivity ($\rho$)

An intrinsic property of a conducting material equal to its resistance per unit length with unit cross-sectional area, given by $\rho = \frac{RA}{L}$ and measured in $\Omega\,\text{m}$.

Ohm's Law

The law stating that for a metallic conductor maintained at a constant temperature, the current flowing through it is directly proportional to the potential difference across it ($I \propto V$).

Ohmic vs. Non-Ohmic Conductors

Ohmic conductors possess a constant resistance, yielding a straight-line $I\text{--}V$ graph passing through the origin; non-ohmic conductors have a variable resistance where the $I\text{--}V$ relationship is non-linear.

Filament Lamp Characteristic

A non-ohmic $I\text{--}V$ curve that flattens at higher voltages because increasing current raises drift speed and lattice ion vibrations, increasing wire temperature and resistance.

Potential Divider

A circuit arrangement of series resistors designed to divide the supply potential difference across components in direct proportion to their individual resistances ($\frac{V_1}{V_2} = \frac{R_1}{R_2}$).

Potentiometer

A three-terminal variable resistor with a sliding contact arranged as a potential divider to provide a continuously variable output voltage ranging from $0\,\text{V}$ up to the full source voltage.

Negative Temperature Coefficient (NTC) Thermistor

A non-ohmic semiconductor sensor whose electrical resistance decreases substantially as temperature rises, due to the thermal release of numerous free charge carriers.

Light-Dependent Resistor (LDR)

A non-ohmic semiconductor component whose electrical resistance falls from megohms ($\text{M}\Omega$) in darkness to tens of ohms ($\Omega$) in bright light as incident photons liberate electrons.

Electrical Power ($P$)

The rate at which energy is transferred or dissipated in an electrical circuit, defined by $P = \frac{W}{t} = IV = I^2R = \frac{V^2}{R}$, measured in watts ($1\,\text{W} = 1\,\text{J}\,\text{s}^{-1}$).

Electromotive Force (emf, $\varepsilon$)

The energy converted from non-electrical forms into electrical energy per unit charge moving through the source, equivalent to the open-circuit terminal potential difference ($\varepsilon = \frac{W}{q}$).

Internal Resistance ($r$)

The electrical resistance inherent to the electrolyte and electrodes within a power source that dissipates thermal energy internally when current flows.

Terminal Potential Difference ($V$) and Lost Volts ($Ir$)

Terminal p.d. is the potential difference across external load resistance ($V = IR$), while lost volts represents the potential drop across internal resistance; during discharge, $V = \varepsilon - Ir$.

Maximum Power Transfer Theorem

The electrical principle establishing that the maximum power output transferred from a source to an external load resistor occurs when the load resistance equals the internal resistance ($R = r$).

Primary Cell

A non-rechargeable electrochemical cell that irreversibly converts chemical energy into electrical energy until its chemical reactants are permanently depleted.

Secondary Cell

A rechargeable electrochemical cell in which electrical energy can reverse the internal chemical reaction to restore its stored chemical potential energy.

Photovoltaic (Solar) Cell

A semiconductor device that converts incident light directly into electrical energy via the photoelectric release of electrons, generating approximately $1\,\text{V}$ emf with roughly $25\%$ efficiency.

Simple Harmonic Motion (SHM)

Periodic oscillatory motion in which acceleration is directly proportional to displacement from the equilibrium position and directed towards that position ($a = -\omega^2 x$).

Isochronous Oscillation

An oscillation whose period remains constant regardless of variations in the amplitude of the motion, a defining property of simple harmonic motion.

Angular Frequency ($\omega$)

A scalar measure of the rotation rate or oscillatory frequency of a body, defined by $\omega = 2\pi f = \frac{2\pi}{T}$, expressed in radians per second ($\text{rad}\,\text{s}^{-1}$).

Phase Difference ($\Delta\phi$)

The horizontal shift or fractional difference in the cycle between two oscillating bodies or waves, determined by $\Delta\phi = \left(\frac{\Delta t}{T}\right) \times 2\pi$ radians (or $\times 360^\circ$).

Transverse Wave

A travelling or stationary wave in which the particles of the medium oscillate perpendicular to the direction of wave propagation and energy transfer.

Longitudinal Wave

A wave in which the particles of the medium oscillate parallel to the direction of wave travel, creating alternating regions of high pressure (compressions) and low pressure (rarefactions).

Wavefront and Ray

A wavefront is an imaginary surface connecting adjacent points vibrating in identical phase; a ray is a directed vector perpendicular to wavefronts showing the direction of energy propagation.

Wave Intensity ($I$)

The radiant power transferred by a wave per unit cross-sectional area perpendicular to the direction of travel ($I \propto \text{amplitude}^2$), obeying $I = \frac{P}{4\pi d^2}$ for isotropic point sources.

Refraction

The change in direction of a wavefront caused by a variation in wave speed when entering a different optical or physical medium.

Snell's Law

The optical relation governing refraction across an interface: $\frac{\sin(i)}{\sin(r)} = \frac{v_1}{v_2} = \frac{\lambda_1}{\lambda_2} = \frac{n_2}{n_1} = \text{constant}$.

Dispersion

The separation of polychromatic radiation into its constituent component wavelengths due to the wavelength-dependence of the refractive index ($n_\text{violet} > n_\text{red}$).

Critical Angle ($c$)

The angle of incidence within an optically denser medium that results in an angle of refraction of exactly $90^\circ$ in the adjacent rarer medium.

Total Internal Reflection (TIR)

The complete reflection of incident light back into an optically denser medium when light strikes a boundary with a rarer medium at an angle of incidence greater than the critical angle ($i > c$).

Diffraction

The bending and lateral spreading of waves around obstacles or through apertures, occurring most prominently when the aperture size ($b$) is comparable to or smaller than the wavelength ($\lambda \ge b$).

Huygens' Principle

The wave principle stating that every point on an advancing wavefront acts as a source of secondary wavelets propagating forward at wave speed, whose forward tangent forms the next wavefront.

Single-Slit Diffraction Minimum

The angular position of zero intensity produced by destructive interference across a slit of width $b$, given for the first minimum by $\theta = \frac{\lambda}{b}$ radians.

Principle of Superposition

The principle stating that when two or more overlapping waves meet at a point in a medium, the net displacement equals the algebraic sum of their individual displacements.

Coherent Sources

Two or more wave sources that emit waves with identical frequency, identical wavelength, and a constant relative phase difference over time.

Fringe Spacing ($s$)

The linear separation between consecutive constructive maxima (or destructive minima) on a screen at distance $D$ from two coherent slits separated by distance $d$, calculated as $s = \frac{\lambda D}{d}$.

Diffraction Grating

A plate possessing thousands of closely spaced parallel slits separated by a distance $d$, producing sharp spectral maxima according to the grating equation $d\sin(\theta) = n\lambda$.

Damping

The continuous dissipation of mechanical oscillatory energy into thermal energy caused by friction or resistive drag forces acting opposite to the direction of motion.

Natural Frequency ($f_0$)

The unforced characteristic frequency at which a mechanical or physical system oscillates freely after being initially displaced from equilibrium.

Resonance

The state attained in a driven oscillator when the periodic driving frequency matches the natural frequency of the system ($f_D = f_0$), producing a sharp peak in oscillation amplitude.

Standing (Stationary) Wave

A wave profile formed by the superposition of two counter-propagating identical waves of equal frequency and amplitude, characterized by stationary nodes and antinodes without net energy propagation.

Node and Antinode

In a standing wave, a node is a permanent position of zero particle displacement, and an antinode is a position of maximum oscillation amplitude; the spacing between adjacent nodes is $\frac{\lambda}{2}$, and between a node and an adjacent antinode is $\frac{\lambda}{4}$.

Frequency Spectrum

A graphical representation plotting relative amplitude against frequency, displaying the fundamental frequency ($f_1$) alongside the discrete harmonic frequencies present within an oscillating source.