Comprehensive Physics: Thermal Energy, Electricity, Electromagnetism, Light, Waves, and Atomic Structure

Vocabulary practice flashcards covering heat transfer, current electricity, electromagnetism, geometric optics, wave properties, and nuclear atomic structure.

Thermal Energy

The combination of internal potential and kinetic energy in a system; in gases, thermal energy is solely due to kinetic energy.

Thermal Equilibrium

The condition reached when two or more objects achieve the exact same temperature and net heat stops flowing between them.

Thermal Conduction

The transfer of thermal energy through direct physical contact via the microscopic collisions and vibrations of atoms and molecules; it represents the slowest method of heat transfer.

Convection

The transfer of heat through the bulk movement of a heated fluid (liquid or gas) driven by circulation currents; it requires a fluid medium and is faster than conduction.

Infrared Radiation

Thermal radiation consisting of electromagnetic waves emitted by warm or hot objects that transfers heat through empty space in straight lines without requiring physical contact or a medium.

Convection Current

A continuous circulating loop in a fluid driven by temperature and density differences, wherein warmer, less dense fluid rises and cooler, denser fluid sinks.

Thermal Insulator

A material or substance (such as wood, trapped air, or hay) that conducts very little thermal energy, thereby preventing unwanted heat transfer.

Thermos Flask

A thermal insulation container with double-walled glass enclosing a vacuum to prevent conduction and convection, and silvered inner surfaces to minimize radiation loss.

Electrical Conductor

A material (such as copper, silver, gold, or steel) that readily conducts electric charge due to the presence of free electrons.

Electrical Insulator

A material (such as polymers, minerals, or glass) that prevents the flow of electric charge because it lacks free electrons.

Electric Current ($I$)

The rate of flow of electric charge through a conductor in a given time period, expressed by the formula $I = \frac{Q}{t} = \frac{ne}{t}$ and measured in amperes ($\text{A}$).

Elementary Charge ($e$)

The fundamental unit of electric charge carried by a single proton or electron, with a magnitude of $1.6 \times 10^{-19}\,\text{C}$.

Conventional Current

The standardized direction of electric current flow from the positive terminal to the negative terminal (higher potential to lower potential), opposite to the flow of electrons.

Potential Difference

The electrical work done by a unit charge passing through a circuit component, measured in volts ($\text{V}$) using a voltmeter connected in parallel.

Electromotive Force (emf)

The total electrical work done by an energy source, such as a cell or battery, in driving charge through a complete circuit, measured in volts ($\text{V}$).

Fuse

An electrical safety device containing a sacrificial metal wire that melts and breaks the circuit when an overcurrent condition occurs, protecting equipment from fire hazards.

Trip Switch

An automatic safety switch that cuts off power upon detecting an overload, short circuit, or electrical fault, functioning as a reusable alternative to a fuse.

Alternating Current (AC)

An electric current whose magnitude continuously varies and whose direction reverses at regular time intervals, commonly produced by an AC generator.

Direct Current (DC)

An electric current that flows unidirectionally through a conductor, commonly provided by chemical batteries or mobile chargers.

Electric Force

The force exerted on a charged particle placed in an electric field, mathematically defined as $F = qE$.

Magnetic Force on a Moving Charge

The deflecting force experienced by a charged particle moving through a magnetic field, defined as $F = qvB$, acting perpendicular to both velocity and magnetic field vectors.

Lorentz Force

The total resultant force acting on a charged particle moving through simultaneous electric and magnetic fields, given by the expression $F = q(E + vB)$.

Fleming's Left-Hand Rule

A mnemonic rule for motors: with the thumb, first finger, and second finger held mutually at $90^\circ$, the First finger represents Magnetic Field, the seCond finger represents Current, and the Thumb represents Motion/Thrust (Force).

Right-Hand Thumb Rule

A visual rule stating that when the thumb of the right hand points in the direction of conventional current along a straight wire, the curled fingers indicate the circular direction of magnetic field lines.

Split-Ring Commutator

A split metal ring in a direct current motor that reverses the direction of current in the armature coil every half-turn to maintain unidirectional rotational torque.

Solenoid

A tightly wound helical coil of insulated wire that generates an internal uniform magnetic field resembling that of a bar magnet when conducting an electric current.

Moving-Coil Loudspeaker

An electroacoustic transducer where alternating electrical signals pass through a voice coil situated in a magnetic field, driving coil movement that vibrates a speaker cone to produce sound waves.

Refraction of Light

The bending of a light ray as it passes across a boundary from one optical medium into another, caused by a change in wave speed.

Lateral Displacement

The perpendicular distance between the path of the original incident ray and the emergent ray after passing through an optical medium with parallel faces, such as a glass slab.

Refractive Index ($\mu$ or $n$)

The ratio of the speed of light in medium 1 to that in medium 2 ($\frac{V_1}{V_2}$), or the ratio of $\frac{\sin(i)}{\sin(r)}$ for a given boundary pair according to Snell's law.

Convex Lens

A converging lens that is thicker in the center than at the edges, which refracts parallel rays toward a real focal point and is commonly used to correct hypermetropia.

Concave Lens

A diverging lens that is thinner at the center than at the edges, causing parallel rays to diverge outwards as if originating from a virtual focal point, used to correct myopia.

Principal Focus (Focal Point)

The focal point on the principal axis of a lens where incident rays running parallel to the axis converge (convex lens) or appear to diverge from (concave lens).

Optical Centre ($O$)

The geometric center point of an optical lens through which light rays pass undeflected and undeviated in a straight line.

Mechanical Wave

A wave oscillation that strictly requires a physical material medium for energy propagation (e.g., sound waves, ocean ripples, seismic waves).

Electromagnetic Wave

A self-propagating transverse wave composed of oscillating electric and magnetic fields that travels through a vacuum without needing a material medium.

Transverse Wave

A wave in which the particles of the medium oscillate perpendicular to the direction in which the wave propagates.

Longitudinal Wave

A wave in which the particles of the medium oscillate parallel to (along) the direction of wave propagation.

P-waves

Fast-moving primary seismic waves that oscillate longitudinally through rock during seismic events.

S-waves

Slower-moving secondary seismic waves that oscillate transversely through the Earth's crust.

Crest and Trough

Features of a transverse wave: a crest is the point of maximum upward displacement from equilibrium, and a trough is the point of maximum downward displacement.

Compression and Rarefaction

Features of a longitudinal wave: a compression is a region where particles are packed closely with high density and pressure; a rarefaction is a region where particles are spread apart with low density and pressure.

Wave Velocity Formula

The equation determining wave propagation speed, given as $v = f \times \lambda$, where $v$ is wave velocity, $f$ is frequency, and $\lambda$ is wavelength.

Diffraction

The spreading or bending of wave fronts as they pass around edges or through gaps, reaching maximum prominence when the gap width equals the wave's wavelength.

Plum Pudding Model

An early atomic model where negatively charged electrons ('plums') are distributed inside a uniform sphere of positive charge ('pudding').

Rutherford Nuclear Atom Model

The atomic model established following Ernest Rutherford's 1909 discovery, stating that an atom features a tiny, central positive nucleus surrounded by orbiting electrons.

Atomic Number ($Z$)

The total number of protons residing within the nucleus of an atom, identifying its chemical identity.

Mass Number ($A$)

The total count of nucleons (protons plus neutrons) found within the nucleus of an atom.

Nucleon

A collective classification for any subatomic particle located within the atomic nucleus, encompassing both protons and neutrons.

Sub-atomic Particles

The three constituent particles of an atom: protons (in nucleus, relative charge $+1$, relative mass $1$), neutrons (in nucleus, relative charge $0$, relative mass $1$), and electrons (orbiting nucleus, relative charge $-1$, relative mass $\frac{1}{1836}$).