ILTS Science: Physics (243) key terms

A testable, provisional explanation for an observed pattern or problem, stated so that evidence could support or contradict it. It guides investigation rather than asserting established fact.

The factor a researcher deliberately changes or selects across conditions in an experiment, so its effect on an outcome can be examined while other factors are held constant.

The measured outcome in an experiment; its value is expected to respond to changes in the independent variable. Researchers record it to test whether a proposed relationship holds.

A factor that is kept constant or treated the same across experimental conditions so it does not confound the relationship between the independent and dependent variables.

A process in which independent experts evaluate a study's methods, evidence, and reasoning before publication or acceptance, helping identify errors, unsupported claims, and gaps.

A well-supported explanation of a broad class of phenomena, built from repeated evidence and tested predictions. In science, theory does not mean a guess or tentative opinion.

The range or estimated amount by which a measured value may differ from the true value because of instrument limits, technique, and random or systematic effects.

A vector quantity giving the straight-line change in position from an initial point to a final point, including both distance and direction; it is not the same as path length.

The rate at which velocity changes with time, including changes in speed, direction, or both. It is a vector quantity and has units of meters per second squared.

The tendency of an object to resist changes in its state of motion. Mass is the quantitative measure of inertia in Newtonian mechanics.

The net force on an object equals its mass times its acceleration, expressed as F = ma when mass is constant. Force and acceleration point in the same direction.

The energy transferred to or from an object when a force acts through a displacement. Only the force component along the displacement does work.

The energy an object possesses because of its motion, equal to one-half its mass times the square of its speed for nonrelativistic motion.

In a closed system with no net external force, the total momentum of the system remains constant; interactions may redistribute momentum among objects but do not change the total.

A vector field describing the electric force per unit positive charge at a point. Its direction is the direction of force on a positive test charge.

The change in electric potential energy per unit charge between two points, often called voltage. It drives current through a conductor when a circuit is closed.

A measure of how strongly a component opposes electric current, equal to the potential difference across it divided by the current through it under ohmic conditions.

For a conductor at constant temperature, current is directly proportional to potential difference and inversely proportional to resistance, commonly written V = IR.

A vector field that exerts magnetic forces on moving charges, currents, and magnetic materials. Its direction is defined by the force on a north-seeking pole.

The generation of an electric potential difference in a conductor when the magnetic flux through a circuit changes, as described by Faraday's law.

The distance between consecutive corresponding points on a periodic wave, such as crest to crest or compression to compression, measured along the direction of propagation.

The number of complete wave cycles or oscillations passing a fixed point per unit time, measured in hertz; it is the reciprocal of period.

The maximum displacement of a wave or oscillation from its equilibrium position. For mechanical waves, greater amplitude generally carries more energy.

The bending of a wave as it crosses a boundary between media where its speed changes. The change in direction follows from Snell's law.

The spreading or bending of waves around obstacles and through openings, becoming most noticeable when the obstacle or opening is comparable to the wavelength.

The superposition of two or more waves, producing regions of greater or lesser amplitude depending on whether their displacements add constructively or destructively.

A measure of the average random kinetic energy of particles in a substance, indicating how hot or cold it is relative to a chosen scale.

Energy transferred between objects or surroundings because of a temperature difference. Heat is a transfer process, not a quantity stored inside an object.

The total microscopic kinetic and potential energy of the particles making up a system. It changes with temperature, phase, and particle interactions.

The change in a system's internal energy equals the heat added to the system minus the work done by the system, expressing energy conservation.

A measure of the number of microscopic arrangements consistent with a system's macroscopic state, often described as a measure of disorder or energy dispersal.

The amount of energy needed to raise the temperature of one kilogram of a substance by one kelvin, reflecting how readily its temperature changes.

A quantum of electromagnetic radiation carrying energy proportional to frequency and no rest mass. Photons mediate electromagnetic interactions and can be absorbed or emitted.

The emission of electrons from a material when light of sufficient frequency strikes it. The effect demonstrates that light delivers energy in discrete packets.

The principle that quantum objects such as electrons and photons exhibit both wave-like and particle-like behavior depending on the experimental arrangement.

The relation E = mc², stating that mass and energy are equivalent and that a small mass corresponds to a large amount of energy.

The time required for half of the radioactive nuclei in a sample to decay, or for half of a sample's activity to disappear.

A reaction in which light atomic nuclei combine to form a heavier nucleus, releasing energy when the resulting nucleus is more tightly bound.