STEM OnLine Mini Dictionary
Black Body
Ideal theoretical object that absorbs all radiation it receives and emits energy according to its temperature.
Black Hole
Region of space with such high density that its gravitational pull prevents even light from escaping.
Block and Tackle
Combined configuration of pulleys that optimizes mechanical effort to move large resistances.
Blueshift
Apparent shortening of the wavelength of light from an object approaching the observer.
Boiling point
Temperature at which the vapor pressure of a liquid equals the external pressure, causing the transition to the gaseous state.
Bond Angle
Angle formed by two chemical bonds sharing the same central atom. The unit of measurement is the sexagesimal degree (°).
Bond Length
Average distance between the nuclei of two atoms joined by a chemical bond. It is usually measured in angstroms (Å) or picometers (pm).
Boyle’s Law
States that, at constant temperature, the volume of a fixed mass of gas is inversely proportional to the pressure (P₁V₁ = P₂V₂).
Branch
Portion of a circuit between two consecutive nodes containing one or more components.
Branch Independence
Property of parallel circuits where the failure or disconnection of a component in one branch does not affect the operation of the others.
Brushes
Fixed contacts (usually graphite) that allow the passage of electric current between the stationary part and the moving part (rotor) of a motor.
Buffer Solution
Chemical mixture that has the ability to resist changes in pH when small amounts of acids or bases are added.
Buoyant Force
Upward vertical force exerted by a fluid on a submerged body, calculated as E = ρ * V * g in the SI (in Newtons).
Calculus
Branch of mathematics analyzing change using derivatives, integrals, and limits to solve continuous problems.
Calorie
Amount of energy required to raise the temperature of one gram of pure water by 1 °C. It is equivalent to 4.184 J.
Capacitance
Ability of a component to store electric charge per unit of potential difference, defined as C = Q / V and measured in Farads (F) in the SI.
Capacitor
Passive component designed to store electrical energy in the form of an electrostatic field between two conductive plates.
Capacitor Charging
Dynamic process in which a capacitor accumulates energy, its voltage increasing exponentially until it equals that of the source.
Capacitor Discharging
Dynamic process in which a capacitor releases stored energy through a resistor, its voltage decreasing exponentially to zero.
Carbon Dioxide
Main greenhouse gas generated by burning fossil fuels and respiration.
Cartesian Plane
A two-dimensional system formed by two perpendicular graduated lines that allow any point to be located using a pair of coordinates $(x, y)$.
Catalyst
Substance that increases the rate of a chemical reaction without being consumed or permanently altered in the process.
Catalytic Electrode
Conductive surface that facilitates the redox reaction of external gases without being consumed or degraded during the process.
Cathetus
Each of the two sides that form the right angle in a right triangle.
Cation
Ion with a positive electrical charge formed when a neutral atom loses one or more electrons.
Celestial Equator
Great circle on the celestial sphere resulting from projecting Earth’s equator into space.
Celestial Meridian
Great circle passing through the celestial poles and an observer’s zenith.
Celestial Pole
Intersection points of Earth’s rotation axis with the celestial sphere.
Celestial Sphere
Imaginary sphere of infinite radius, centered on the Earth, onto which celestial bodies are projected.
Center of Buoyancy
Point where the buoyant force is considered to be applied, coinciding with the center of gravity of the displaced fluid volume.
Center of Gravity
Specific point where the resultant gravitational force of a body is considered to act.
Center of Mass
Geometric point where the entire mass of a system is considered concentrated for motion analysis.
Centrifugal Force
Apparent force that tends to move a body away from the center of rotation when observed from an accelerated system.
Centripetal Acceleration
Quantity that measures the change in velocity direction of a body following a curved path.
Centripetal Force
Net force directed toward the center of the trajectory that forces a body to follow a curve.
Chain Reaction
Fission process where released neutrons strike other heavy nuclei, causing a series of successive and self-sustained fissions.
Change in Momentum
Change experienced in a body’s momentum, which is numerically equal to the received impulse.
Charles’s Law
States that, at constant pressure, the volume of a gas is directly proportional to its absolute temperature (V₁/T₁ = V₂/T₂).
Chemical Bond
Set of forces that hold atoms, ions, or molecules together to form more complex and stable structures.
Chemical Compound
Substance formed by the chemical union of two or more elements in defined proportions.
Chemical Element
Pure substance formed by atoms with the same number of protons.
Chemical Energy
Potential energy stored in chemical bonds that is released or absorbed during a reaction.
Chemical Equation
Symbolic representation of a chemical reaction showing the substances that react and those that are produced.
Chemical Law
General relationship experimentally verified that describes the behavior of chemical substances.
Chemical Model
Simplified representation of chemical substances or processes allowing study and prediction.
Chemical Property
Characteristic of a substance describing its behavior during a chemical transformation.
Chemical Quantity
Measurable property of a chemical system expressed using a numerical value and a unit.
Chemical Reaction
Thermodynamic process in which one or more substances transform their molecular structure and bonds to form new substances.
Chromatic Aberration
Optical defect common in refractors where colors do not focus at the same point, creating colored edges.
Dalton’s Law
States that the total pressure of a gas mixture is equal to the sum of the partial pressures of each individual gas.
Damping
Energy dissipation process in an oscillatory system that gradually reduces the amplitude of motion.
Data Distribution
The way the values of a variable are organized and spread, allowing for the identification of patterns and trends.
Declination
Celestial coordinate equivalent to latitude, measured north or south of the celestial equator.
Decomposition Potential
Minimum external voltage that must be applied to an electrolytic cell for electrolysis to occur continuously.
Decomposition Reaction
Process in which a single compound fragments into two or more simpler substances.
Definition
Precise explanation of the meaning of a concept within a formal system.
Deformation
Change in the length or shape of an elastic body (stretching or compression) relative to its equilibrium position.
Degree
Angular measurement unit that divides a circle into 360 equal parts (°).
Degree Celsius
Temperature unit based on the freezing (0 °C) and boiling (100 °C) points of water at standard pressure.
Degree Fahrenheit
Temperature scale where the freezing point of water is 32 °F and the boiling point is 212 °F.
Denominator
The lower number that determines how many equal parts the unit is divided into; it can never be zero due to mathematical impossibility.
Density
Scalar quantity expressing the amount of mass per unit volume of a substance, measured in kg/m³ in the SI.
Dependent Variable
A magnitude whose value is determined by the function’s correspondence rule when applied to the independent variable.
Derivative
A function that measures the rate of change of one variable with respect to another, mathematically representing the slope of the curve at each point.
Destructive Interference
Phenomenon that occurs when waves meet in phase opposition, subtracting their amplitudes and potentially canceling each other out.
Deuterium
Stable isotope of hydrogen containing one proton and one neutron in its nucleus.
Dew Point
Specific temperature to which an air mass must be cooled to reach saturation and begin condensation.
Diagonal
A line segment connecting two non-consecutive vertices of a polygon.
Diatomic Gas
Molecule formed by two atoms of the same element, as occurs with elemental hydrogen in nature.
Dielectric
Insulating material that, when placed between the plates of a capacitor, increases its capacitance by reducing the internal electric field.
Dielectric Strength
Maximum electric field intensity that an insulator can withstand before becoming conductive (breakdown).
Differentiability
A property of a function that guarantees the existence of its derivative at a given point or interval.
Diffuse Reflection
Scattering of light in multiple directions when striking a rough surface, preventing the formation of sharp images.
Diffusion
Process by which the particles of one gas gradually mix with those of another due to their random thermal motion.
Digital Circuit
Electrical circuit operating with discrete signals represented by defined levels.
Dilution
Procedure that consists of decreasing the concentration of a solute by adding more solvent.
Diminished Image
Type of image produced by diverging lenses that is always smaller in size than the actual object.
Direct Current
Type of electric current in which charges move always in the same direction.
Direct Proportion
A relationship where an increase in one magnitude causes a proportional increase in the other, keeping their quotient constant.
Direct Proportionality
Relationship in a voltage divider where a higher resistance corresponds to a higher voltage drop (V ∝ R).
Direction
The straight line upon which the vector lies, defined by the angle it forms with the reference axes.
Displaced Volume
Space occupied by the fluid that has been moved aside by the body upon immersion, measured in m³ in the SI.
Displacement
Vector quantity that measures the change in position of an object from its initial point to its final point.
Dissipated Power
Part of the electrical power that is lost in the form of heat due to the resistance of components or conductors.
Dissipative Force
Force that transforms work into non-recoverable energy, usually heat (such as friction), depending on the path.
Electrolytic Cell
Electrochemical system that consumes electrical energy to induce a non-spontaneous chemical reaction where the Gibbs free energy change is greater than zero.
Electromagnetic Induction
Process by which an electric current is generated in a conductor when it is exposed to a changing magnetic field.
Electromagnetic Spectrum
Energy distribution of the set of all electromagnetic waves, ranging from radio waves to gamma rays.
Electromagnetic Wave
Perturbation of electric and magnetic fields that self-propagates in a vacuum, carrying energy without the need for a material medium.
Electromagnetism
Branch of physics studying electric and magnetic phenomena and their interactions.
Electromotive Force (EMF)
Potential difference generated by a non-electrical source (such as a changing magnetic field), measured in Volts (V) in the SI.
Electron
Subatomic particle with a negative electrical charge of -1.602 × 10⁻¹⁹ C orbiting the atomic nucleus.
Electron Cloud
Outer region of the atom surrounding the nucleus where electrons are distributed in different energy levels.
Electronegativity
Measure of an atom’s ability in a molecule to attract towards itself the electrons shared in a chemical bond.
Electronic Transition
Displacement of an electron between two allowed energy levels, mediated by the absorption or emission of a photon.
Electrostatic Attraction
Phenomenon occurring when two charges of opposite signs experience a force tending to pull them together.
Electrostatic Force
Fundamental force of attraction or repulsion acting between electrically charged bodies, described by Coulomb’s law.
Electrostatic Repulsion
Phenomenon occurring when two charges of the same sign experience a force tending to push them apart.
Elongation
Distance or angle that separates the oscillating body from its equilibrium position at a given instant.
Endothermic Reaction
Chemical reaction that requires the absorption of energy from the surroundings to take place.
Energy
Capacity of a physical system to perform work or produce changes, measured in the International System in joules (J).
Energy Degradation
Transformation of useful forms of energy into less usable forms, generally residual thermal energy.
Energy Density
Amount of energy stored per unit of mass or volume, a critical parameter for comparing the efficiency of different battery systems.
Energy Dissipation
Transformation of kinetic energy into heat due to the work performed by the friction force.
Energy Efficiency
Ratio between the useful energy obtained in a process and the total energy consumed during it.
Energy Quantization
Principle stating that electrons can only exchange energy in specific, discrete amounts.
Energy Quantum
Minimum and indivisible amount of energy that can be absorbed or emitted as electromagnetic radiation.
Epicenter
Point on the Earth’s surface located vertically above the hypocenter; it is located using geographical coordinates.
Epicycle
Imaginary circle used in the geocentric model to explain the apparent motion of the planets.
Equal Sign
A mathematical symbol indicating that the expressions on both sides have exactly the same value or meaning.
Equation Balancing
Process of adjusting coefficients so that the number of atoms of each element is equal on both sides of the equation.
Equation of Continuity
Principle stating that for an incompressible fluid the flow rate remains constant (A1 * v1 = A2 * v2).
Equilibrium of Forces
Situation in which the sum of all forces acting on an object is zero, resulting in zero acceleration.
Equinox
Time of year when the Sun crosses the celestial equator and day and night are of equal length.
Equivalence Principle
Postulate stating that the effects of gravity are indistinguishable from the effects of acceleration.
Equivalent Fractions
Expressions that, despite having different numbers, represent the same proportion or decimal value after division.
Equivalent Resistance
A single resistance that could replace all those in the circuit producing the same effect; it is calculated by simplifying the circuit in stages.
Escape Velocity
Minimum speed for an object to escape the gravitational pull of a celestial body. Usually measured in kilometers per second (km/s).
Evaluation of a Function
The procedure of substituting the independent variable with a number to find its corresponding value in the function.
Event
A subset of the sample space representing one or more specific outcomes to which a probability can be assigned.
Excited State
Condition of an atom after absorbing energy, where an electron occupies a higher energy orbital than the ground state.
Ground State
Lowest and most stable energy level in which an electron can be found within an atom.
Half-life
Time required for half of the nuclei in a radioactive sample to decay into a different element.
Harmonics
Sinusoidal components of the series whose frequencies are integer multiples of the fundamental frequency.
Heat
Thermal energy in transit from one body to another. It is measured in Joules (J), though the calorie (cal) is used, where 1 cal = 4.184 J.
Height
The perpendicular distance measured from the base to the furthest point or vertex of a figure.
Heliocentric Model
Astronomical theory that places the Sun at the center of the system and the planets revolving around it.
High Tide
The moment when sea water reaches its maximum height within the tidal cycle; it is measured in meters (m) or feet (ft) relative to the mean level.
Hohmann Transfer Orbit
Orbital maneuver that uses two engine pulses to move a spacecraft between two circular orbits.
Homologous Series
Group of organic compounds with the same chemical function that differ only by the number of methylene groups.
Hooke’s Law
Physical principle stating that the force exerted by a spring is proportional to its deformation, measured in joules (J) regarding work performed.
Horizontal Displacement
Change in position of an object measured exclusively along the axis parallel to the horizon.
Hydration
Ability of some salts to incorporate water molecules into their crystal structure in a constant manner.
Hydraulic Press
Device that multiplies a force through the area ratio F1 / A1 = F2 / A2, based on Pascal’s principle.
Hydride
Chemical compound formed by the combination of hydrogen with any other element, whether metallic or non-metallic.
Hydrogen
Chemical element with atomic number 1, the lightest in the periodic table, which under normal conditions occurs as a diatomic gas (H₂).
Hydrogen Bond
Especially strong dipole-dipole interaction between the hydrogen atom of one water molecule and the oxygen of another.
Hydrostatic Pressure
Pressure due to the weight of a fluid at rest, calculated as P = ρ · g · h and measured in Pascals (Pa) in the SI.
Hygrometer
Precision instrument designed to measure the moisture content in the atmosphere.
Hyperopia
Visual defect where images are focused behind the retina; it is corrected through the use of convex lenses.
Hypocenter
Point inside the Earth where the rupture that generates the seism originates; its depth is measured in kilometers (km).
Hypotenuse
The longest side in a right triangle, opposite the right angle.
Ice Sheet
A mass of glacial ice covering more than 50,000 km² of land and flowing in all directions (e.g., Antarctica and Greenland).
Ideal Gas
Theoretical gas composed of point particles with random displacements that do not interact with each other, following the gas laws.
Ideal Gas Law
Equation of state relating pressure, volume, temperature, and moles of a gas through the expression PV = nRT.
Image of a Point
The specific value returned by the function when evaluated at a concrete value within its domain.
Impact Force
Intense force acting over a very short period of time, characteristic of collisions and crashes.
Impedance
Total opposition a circuit offers to the flow of alternating current; it combines resistance and reactances, measured in Ohms (Ω).
Improper Fraction
A fraction whose numerator is equal to or greater than the denominator, indicating the value is equal to or greater than one whole.
Impulse
Vector quantity product of the applied force by the time interval of action, measured in N·s.
Impulse-Momentum Theorem
Physical relationship stating that the impulse applied to a body equals the change in its linear momentum.
Incident Ray
Light beam that propagates toward a reflective surface before interacting with it.
Inclination
Degree of deviation of a surface or line from the horizontal or vertical.
Inclined Plane
Flat surface forming an angle with the horizontal plane, used to raise or lower bodies with less effort.
Incompressible Fluid
Substance whose density is assumed constant (ρ = constant in the SI) under pressure changes, such as most liquids.
Increment (Δx)
The difference or variation between two values of the independent variable used to calculate the rate of change.
Independence of Motions
Principle that allows decomposing a complex motion into simultaneous simple motions that do not interfere with each other.
Independent Event
An event whose probability of occurrence is not affected by the previous outcome of another distinct event.
Magnetic Declination
Angle between true north and the north indicated by a compass.
Magnetic Dipole
System composed of two opposite poles (north and south); isolated magnetic poles (monopoles) do not exist in nature.
Magnetic Energy
Energy accumulated within the magnetic field generated by the inductor during the passage of electric current.
Magnetic Field
Region of space where a moving electric charge experiences a magnetic force, measured in Teslas (T) in the SI.
Magnetic Flux
Measure of the amount of magnetism passing through a surface, calculated as Φ = B · A · cos(θ) and measured in Webers (Wb) in the SI.
Magnetic Permeability
Ability of a material to allow magnetic field lines to pass through it, measured in H/m in the SI.
Magnetic Pole
Point on the Earth’s surface where the magnetic field lines are vertical.
Magnetic Reversal
Event in which the Earth’s magnetic north and south poles swap positions.
Magnetosphere
Region around the Earth dominated by its magnetic field that deflects solar wind.
Magnification
Ratio between the size of the formed image and the actual size of the object observed through the lens.
Magnifying Glass
Optical instrument consisting of a short-focal-length convex lens that produces a virtual, upright, and enlarged image.
Magnitude
Any physical or mathematical property that can be measured or counted and expressed through a numerical value.
Mantle
Intermediate layer of the Earth located between the crust and the core.
Mars
Fourth planet, called the Red Planet due to the iron oxide on its surface.
Mass
Amount of matter in a body, constant throughout the universe. The SI unit of measurement is the kilogram (kg) and in the English system the pound (lb).
Mass Number
Sum of the number of protons and neutrons present in the nucleus of an atom, represented by the letter A.
Mass-Energy Equivalence
Physical principle stating that the energy released in a nuclear reaction comes from a small loss of mass during the process.
Materials Chemistry
Branch of chemistry studying structure, properties, and applications of solid and functional materials.
Mathematical Equality
A proposition of equivalence between two expressions separated by the = sign, indicating they both represent the same logical value.
Mathematical Function
A dependency relationship between two magnitudes where each input value corresponds to exactly one output value.
Mathematical Ratio
A binary link between two magnitudes expressed as a quotient to determine how many times one contains the other.
Maximum Kinetic Energy
Excess energy possessed by the electron after being released, which depends solely on the frequency of the incident light.
Measurement Resolution
The smallest variation in the measured quantity that the instrument is capable of detecting and displaying on its screen.
Measuring Instrument
Device used to measure electrical quantities within a circuit.
Mechanical Advantage
Numerical ratio indicating how much the applied force is multiplied in a simple machine relative to the resistance.
Mechanical Energy
Sum of the kinetic energy and potential energy of a body or system in a given state.
Mechanical Wave
Type of wave that strictly requires a material medium (solid, liquid, or gas) in order to propagate.
Mechanical Work
Scalar quantity resulting from force by displacement and the cosine of the angle between them, measured in joules (J).
Median
The central value of an ordered data set that divides the sample into two equal parts, with 50% of the data above and 50% below.
Melting point
Temperature at which a substance changes from solid to liquid state at a given pressure.
Member
Each of the two expressions located on either side of the equal sign; called the first and second members.
Membrane Electrolyte
Selective barrier that allows the passage of specific ions between electrodes while blocking the direct passage of electrons and gases.
Mercalli Scale
Qualitative scale that measures seismic intensity based on observed effects and damage to people and structures.
Mesh (Loop)
Any closed path in a circuit that does not contain other closed paths within it.
Mesh Equation
Mathematical expression resulting from applying the voltage law to a closed path to find unknown currents.
Mesosphere
Middle layer of the atmosphere where temperature reaches its lowest levels and most meteoroids disintegrate.
Paraffin
Technical name for alkanes highlighting their low reactivity towards most chemical reagents.
Parallel Circuit
Configuration where components are connected to the same nodes, sharing the same voltage but splitting the current.
Parallel Inductors
Configuration where inductor terminals are connected to common points, decreasing the total equivalent inductance of the circuit.
Parallel Measurement
Connection method of an instrument (such as a voltmeter) where it is placed between the two points whose potential difference is to be known.
Parallel Plate Capacitor
Device consisting of two parallel conductors separated by an insulator, whose capacitance is calculated as C = ε · A / d.
Partial Pressure
Pressure that an individual gas in a mixture would exert if it alone occupied the entire volume of the container at the same temperature.
Partial Voltage Drop
Decrease in electric potential in a specific section of the mixed circuit, depending on the local configuration of that section.
Pascal’s Principle
Law stating that pressure exerted at any point in a fluid is transmitted with equal intensity in all directions.
Passive Elements
Components that consume or store electrical energy without generating power gain, such as resistors, capacitors, and coils.
Path Difference
Extra distance one wave travels relative to another to reach the same point, defined by the relationship Δx = x2 – x1.
Pendulum Length
Distance measured from the suspension point to the center of mass of the oscillating body.
Penumbra
Region of partial shadow surrounding the umbra during an eclipse.
Perfectly Inelastic Collision
Case where bodies remain joined after impact, resulting in the maximum possible loss of kinetic energy.
Periapsis
Point in an orbit where the celestial body is at its minimum distance from its center.
Perigee
Point in the lunar orbit where the Moon is closest to the Earth.
Perimeter
The total length of a polygon’s boundary, obtained by summing the measures of all its sides.
Period
Time required for an object in circular motion to complete one full revolution or turn.
Periodic Function
A function that repeats its values at regular intervals of time or space, called periods.
Permafrost
A layer of soil or rock that remains continuously frozen for at least two consecutive years.
Permittivity
Property of a material or vacuum that describes how much it allows or opposes the formation of an electric field within it.
pH
Logarithmic measure indicating the concentration of hydrogen ions in a solution. Its scale typically ranges from 0 (very acidic) to 14 (very basic).
pH Indicator
Chemical substance that changes color depending on the acidity or basicity level of the solution it is in.
pH Meter
Precision electronic instrument used in the laboratory to measure the pH value of a solution using an electrode.
pH Scale
Numerical range used to specify the acidity or basicity of an aqueous solution.
Phase
State of vibration of a particle at a given instant, defined by the angle that determines its position and direction of motion.
Phase Angle
Time or angular difference between the voltage and current peaks in an alternating current circuit.
Phase Difference
Measure of the relative separation in the cycle of two waves at a given point, usually expressed in radians.
Phase Shift
Angle indicating how much a wave is leading or lagging relative to another at a specific instant.
Photocurrent
Flow of electrons released by the photoelectric effect that generates a measurable electric current in a circuit.
Photoelectric Cell
Electronic device that uses the photoelectric effect to convert light energy directly into electrical energy.
Photoelectric Effect
Emission of electrons from a material when exposed to electromagnetic radiation of sufficiently high frequency.
Photon
Quantum of electromagnetic radiation representing the minimum unit of interaction between light and electrons.
Photosphere
Luminous surface of the Sun that emits most of the radiation we receive.
Physical Chemistry
Branch of chemistry studying physical principles that explain the behavior of chemical systems.
Physical Law
Proposition describing a universal behavior in nature based on repeated observations.
Physical Model
Simplified representation of a physical system allowing its study and prediction.
Quadrant
Each of the four regions into which the axes divide the Cartesian plane, numbered I to IV in a counterclockwise direction.
Quantization
Phenomenon by which physical quantities such as energy cannot vary continuously, but in discrete steps or packets”.”
Quantum Algorithm
Sequence of logical operations executed on a quantum computer to perform specific tasks with superior efficiency.
Quantum Computing
Computing paradigm that leverages phenomena such as superposition and entanglement to solve problems unreachable for classical computers.
Quantum Cryptography
Secure communication method that uses the laws of quantum physics to detect any attempt at data interception.
Quantum Decoherence
Process by which a quantum system loses its superposition properties due to interaction with the environment, becoming classical”.”
Quantum Entanglement
Intimate connection between particles where the state of one instantaneously depends on the state of the other, regardless of the distance separating them.
Quantum Mechanics
Branch of physics describing the behavior of matter and energy at atomic scales, where the laws of classical physics are no longer valid.
Quantum Probability
Measure of the possibility of a system being in a certain state after a measurement is performed, replacing classical certainty.
Quantum State
Physical condition describing all measurable properties of a system at the subatomic level at a given moment.
Quantum Supremacy
Point at which a quantum computing device can perform a calculation that is practically impossible for the most powerful classical supercomputer.
Quantum Teleportation
Process of transferring quantum state information to a remote location using entanglement and classical communication.
Qubit (Quantum Bit)
Basic unit of quantum information that, thanks to superposition, can represent 0, 1, or both states simultaneously.
Radial Velocity
Component of an object’s velocity that moves directly away from or toward the observer.
Radian
Angle measurement unit in the SI representing the central angle whose arc length is equal to the radius; it is approximately equal to 57.29°.
Radiant Energy
Energy transmitted through electromagnetic waves that can propagate through a vacuum.
Radiative Forcing
Change in the atmosphere’s net energy flow caused by climate factors.
Radio Telescope
Specialized antenna that captures radio waves from astronomical sources in space.
Radioactivity
Spontaneous process of decay of unstable atomic nuclei through the emission of particles and electromagnetic energy.
Radius of Curvatura
Design parameter defining the shape of the lens surface and determining its ability to converge or diverge light.
Radius of Rotation
Constant distance between the center of the circular path and the position of the moving particle.
Random Experiment
A process or action whose exact outcome cannot be predicted with certainty before it occurs, even under the same initial conditions.
Range or Image
The subset of values in the codomain that are actually reached by the function when the full domain is applied.
RC Circuit
Electrical configuration consisting of a resistor and a capacitor that exhibits time-dependent dynamic behavior.
Reactance
Opposition to the flow of alternating current due to inductance or capacitance, causing a phase shift between voltage and intensity.
Reactant
Initial substance that participates in a chemical reaction and is consumed to form new products.
Real Focal Point
Point where light rays physically converge after passing through a convex lens, allowing images to be projected.
Real Gas
Gas that does not behave exactly according to ideal laws due to intermolecular interactions and the actual volume of its particles.
Real Image
Image formed by the actual convergence of reflected rays, which can be projected onto a surface.
Real Numbers
The set comprising all rational and irrational numbers, allowing for the infinite continuity of the number line.
Reciprocal
The result of transposing the terms of a fraction; multiplying it by the original fraction always results in the number one.
Redshift
Phenomenon where an object’s light shifts toward longer wavelengths because it is moving away from the observer.
Reflected Ray
Light beam that moves away from the surface after bouncing off the point of incidence.
Reflecting Telescope
Instrument that uses curved mirrors instead of lenses to collect and focus light.
Reflexive Property
An axiom stating that every quantity is equal to itself (a = a), a fundamental basis of identity.
Refracted Ray
Light beam that, after passing through the separation surface between two media, continues its propagation in a different direction.
Salt
Chemical compound formed by cations and anions through an ionic bond, typical result of the reaction between an acid and a base.
Salt Hydrolysis
Reaction of the ions of a dissolved salt with water, which can alter the pH of the solution.
Sample
A representative subset selected from a population upon which statistical observations and measurements are performed.
Sample Space
The set of all possible outcomes that can result from a given random experiment.
Satellite
Body orbiting a planet, natural or artificial.
Saturated Air
State in which the air contains the maximum possible amount of water vapor for a given temperature (100% relative humidity).
Saturated Hydrocarbon
Organic compound containing the maximum possible number of hydrogen atoms per carbon, with no double or triple bonds.
Saturation
State of a solution containing the maximum amount of solute that the solvent can hold at a given temperature.
Saturn
Gas giant famous for its extensive and bright ring system.
Scale
A constant proportion of measurement that establishes the unit distance between numbers, ensuring a coherent graphic representation.
Scatter Plot
A two-dimensional graphical representation of data where each point represents the value of two variables, allowing visual identification of their correlation.
Sea Breeze
Local wind blowing from the sea toward the land during the day.
Secant Line
A line that intersects a curve at two points; its slope represents the average rate of change between those two values.
Seism
A synonym for earthquake, commonly used in technical contexts to refer to any vibratory movement of the earth.
Seismic Wave
Elastic wave that propagates the energy of an earthquake; its propagation speed is measured in kilometers per second (km/s).
Seismograph
Precision instrument used to detect, measure, and record Earth’s vibrations.
Self-Induction
Phenomenon by which a changing current in a coil induces an electromotive force within itself to oppose the change in flux.
Semi-major Axis
Half of the longest diameter of an ellipse, used to define the size of an orbit.
Semiconductor
Material whose ability to conduct electricity is intermediate and can be controlled under certain conditions.
Sense
The orientation of the vector’s arrow, indicating towards which end of the direction it is headed.
Series Circuit
Configuration where components are connected one after another, so that the same current flows through all of them.
Series Inductors
Configuration where coils are connected one after another, directly adding their values to obtain a higher equivalent inductance.
Series Measurement
Connection method of an instrument (such as an ammeter) where the current must mandatorily pass through the equipment.
Short Circuit
Path of virtually zero resistance joining two points of different potential, causing a dangerous increase in current.
Short-Circuit Current
Maximum current delivered by the original circuit when its two output terminals are directly connected to each other with zero resistance.
Simple Harmonic Motion
Periodic back-and-forth motion in which a body oscillates about an equilibrium position under the action of a restoring force.
Simple Pendulum
Idealized model consisting of a point mass suspended from an inextensible, weightless string.
Simplification
The technique of reducing a fraction to its lowest terms by dividing both the numerator and denominator by a common divisor.
Sine
Trigonometric ratio defined as the quotient between the side opposite an angle and the hypotenuse.
Sinusoidal Waves
Smooth mathematical functions describing repetitive oscillations, fundamental for signal analysis.
Sliding
Relative motion between two surfaces in contact without rolling.
Slope
A measure of the inclination of a line relative to the horizontal axis, calculated as the ratio of vertical change to horizontal change.
Slope of the Curve
A numerical value indicating the steepness of the tangent line to the function at a specific point in the domain.
Snell’s Law
Principle relating the refractive indices of two media to the angles of incidence and refraction of light.
Solar Corona
Outermost layer of the Sun’s atmosphere, made of plasma and visible during total eclipses.
Solar Declination
Angle between the Sun’s rays and the plane of the Earth’s equator.
Tangent
Trigonometric ratio defined as the quotient between the opposite side and the adjacent side to an angle.
Tangent Line
A straight line that touches a curve at a single given point and whose slope is equal to the derivative of the function at that point.
Telescope
Optical instrument designed to observe distant objects by collecting electromagnetic radiation.
Temperature
Measure of the average kinetic energy of the particles in a system. It is measured in Kelvin (K), degrees Celsius (°C), or Fahrenheit (°F).
Temperature Coefficient
Factor indicating how the resistance of a material changes with temperature, generally increasing in metals.
Tensile Force
Force transmitted through a stretched flexible object, such as a rope, cable, or chain, pulling on objects at its ends.
Tension
Force exerted by a rope or cable that acts as the physical cause of centripetal acceleration.
Term
Each of the parts separated by addition or subtraction signs within the members of an equality.
Terminal Velocity
Constant maximum speed reached by a falling object when air resistance balances its weight.
Test Lead (Probe)
Insulated metal connectors that allow physical contact to be established between the measuring equipment and the circuit points.
The Moon
Earth’s only natural satellite that influences tides and stabilizes the Earth’s axis.
Theorem
Mathematical proposition provable from axioms and definitions within a logical system.
Thermal Balance
Equilibrium between incoming solar energy and heat energy leaving for space.
Thermal Conductivity
Measure of a substance’s ability to transfer heat through its mass.
Thermal Energy
Internal energy of a system due to the chaotic motion of its particles, manifested as temperature.
Thermal Equilibrium
State in which two bodies in contact reach the same temperature and net heat exchange ceases.
Thermodynamics
Branch of physics studying energy, heat, and the transformations of systems.
Thermosphere
Outer layer of the atmosphere where gas molecules absorb high-energy solar radiation, reaching very high temperatures.
Thévenin Equivalent Circuit
Simplified model that reproduces the same electrical behavior (V, I) as the original network from the load’s perspective.
Thévenin Resistance
Resistance seen from the load terminals when all independent internal sources have been zeroed out (voltage sources short-circuited).
Thévenin Voltage
Open-circuit voltage between the network terminals; it represents the electromotive force of the equivalent model.
Thévenin’s Theorem
Principle that allows replacing any linear network with an equivalent circuit consisting of a single voltage source and a series resistor.
Thin Lens
Transparent optical device whose thickness is negligible compared to the radii of curvature of its surfaces.
Threshold Frequency
Minimum frequency of incident light below which no electron emission occurs, regardless of intensity.
Tidal Current
Horizontal movement of water towards the coast (flood) or towards the sea (ebb) due to the variation in sea level.
Tidal Range
Vertical difference in height between consecutive high and low tides; expressed in meters (m) or feet (ft).
Tide
Periodic change in sea level produced mainly by the gravitational forces exerted by the Moon and the Sun on the Earth.
Time Constant
Temporal parameter calculated as the ratio of inductance to resistance that defines how quickly the current responds to circuit variations.
Time Dilation
Phenomenon where time passes more slowly for an observer moving at high speed compared to one at rest.
Time Domain
The representation of a function or signal based on its evolution over time.
Torricelli’s Experiment
Scientific test that proved air has weight and can support a 760 mm mercury column at sea level.
Torricellian Vacuum
Airless space created at the top of a mercury tube when performing Torricelli’s experiment; it was the first evidence of a man-made vacuum.
Torsion Pendulum
System consisting of a body suspended from an elastic wire that oscillates through the rotational deformation of the material.
Total Internal Reflection
Phenomenon where light reflects completely within a medium (like optical fiber) when striking at an angle greater than the critical angle.
Traction
Ability of a wheel or tire to grip a surface without sliding to generate motion.
Trade Wind
Constant wind blowing from the tropics toward the equator.
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