Physics Dictionary A-Z

A Dictionary of Physics

A
Absolute zero - lowest possible temperature at which gas would have a zero volume.
Absorption spectrum - spectrum of electromagnetic radiation absorbed by matter when radiation of all frequencies is passed through it.
Acceleration - change in velocity divided by time interval over which it occurred.
Accuracy - closeness of a measurement to the standard value of that quantity.
Achromatic lens - lens for which all light colours have the same focal length.
Action-reaction forces - pair of forces involved in an interaction that are equal in magnitude and opposition in direction.
Activity - number of decays per second of a radioactive substance.
Adhesion - force of attraction between two unlike materials.
Air resistance - force of air on objects moving through it.
Alpha decay - process in which a nucleus emits an alpha particle.
Alpha particle - positively- charged particles consisting of two protons and two neutrons emitted by radioactive materials.
Ammeter - device to measure electrical current.
Amorphous solid - solids that have no long- range order; no crystal structure.
Ampere - unit of electric current; one ampere is the flow of one coulomb of charge per second.
Amplitude - in any periodic motion, the maximum displacement from equilibrium.
Angle of incidence - angle between direction of motion of waves and a line perpendicular to surface the waves are striking.
Angle of reflection - angle between direction of motion of waves and a line perpendicular to surface the waves are reflected from.
Angle of refraction - angle between direction of motion of waves and a line perpendicular to surface the waves have been refracted from.
Angular momentum - quantity of rotational motion. For a rotating object, product of moment of inertia and angular velocity.
Annihilation - process in which a particle and its antiparticle are converted into energy.
Antenna - device used to receive or transmit electromagnetic waves.
Antineutrino -subatomic particle with no charge or mass emitted in beta decay.
Antinode -point of maximum displacement of two superimposed waves.
Archimedes’ principle - object immersed in a fluid has an upward force equal to the weight of the fluid displaced by the object.
Artificial radioactivity - radioactive isotope not found in nature.
atomic mass unit - unit of mass equal to 1/12 the atomic mass of carbon- 12 nucleus.
Atomic number - number of protons in the nucleus of the atom.
Average acceleration - acceleration measured over a finite time interval
Average velocity - velocity measured over a finite time interval.


B

Back-EMF -potential difference a cross a conductor caused by change in magnetic flux.
Band theory - theory explaining electrical conduction in solids.
Baryon - subatomic particle composed of three quarks. Interacts with the strong nuclear force.
Battery -device that converts chemical to electrical energy consisting of two dissimilar conductors and an electrolyte.
Beat -slow oscillation in amplitude of a complex wave
Bernoulli’s principle - when a fixed quantity of fluid flows, the pressure is decreased when the flow velocity increases.
Beta decay - radioactive decay process in which an electron or positron and neutrino is emitted from a nucleus.
Beta particle - high speed electron emitted by a radioactive nucleus in beta decay.
Binding energy - negative of the amount of energy needed to separate a nucleus into individual nucleons.
Boiling point - temperature at which a substance, under normal atmospheric pressure, changes from a liquid to a vapor state.
Breeder reactor - nuclear reactor that converts nonfissionable nuclei to fissionable nuclei while producing energy.
Bubble chamber - instrument containing superheated liquid in which the path of ionizing particles is made visible as trails of tiny bubbles.
Buoyant force - upward force on an object immersed in fluid.

C
Calorimeter - device that isolates objects to measure temperature changes do to heat flow.
Candela - unit of luminous intensity.
Capacitance - ratio of charge stored per increase in potential difference.
Capacitor - electrical device used to store charge and energy in the electrical field.
Capillary action - rise of liquid in narrow tube due to surface tension.
Carnot efficiency - ideal efficiency of heat engine or refrigerator working between two constant temperatures.
Centripetal force - force that causes centripetal acceleration.
Chain reaction - nuclear reaction in which neutrons are produced that can cause further reactions.
Charged - object that has an unbalance of positive and negative electrical charges.
Charging by conduction - process of charging by touching neutral object to a charged object.
Charging by induction - process of charging by bringing neutral object near charged object, then removing part of resulting separated charge.
Chromatic aberration - variation in focal length of lens with wavelength of light.
Circular motion - motion with constant radius of curvature caused by acceleration being perpendicular to velocity.
Clock reading - time between event and a reference time, usually zero.
Closed, isolated system - collection of objects such that neither matter nor energy can enter or leave the collection.
Closed-pipe resonator - cylindrical tube with one end closed and a sound source at other end.
Coefficient of friction - ratio of frictional force and the normal force between two forces.
Coefficient of linear expansion - change in length divided by original length and by temperature change.
Coefficient of volume expansion - change in volume divided by original volume and by temperature change.
Coherent waves - waves in which all are in step; are in phase.
Cohesive force - attractive force between similar substances.
Complementary colour - two colours that, when added , produce white light. Two pigments, that when combined, produce black.
Compound machine - machine consisting of two or more simple machines.
Compton effect - interaction of photons, usually X rays, with electrons in matter resulting in increased wavelength of X rays and kinetic energy of electrons.
Concave lens - lens thinner in center than edges; a diverging lens.
Concave mirror - converging mirror, one with center of curvature on reflecting side of mirror.
Conduction band - energies of charge carries in a solid such that the carries are free to move.
Conductor - materials through which charged particles move readily; or heat flow readily.
Conserved properties - property that is the same before and after an interaction.
Consonance -two or more sounds that, when heard together, sound pleasant.
Constant acceleration - acceleration that does not change in time.
Constant velocity - velocity that does not change in time.
Constructive interference - superposition of waves resulting in a combined wave with amplitude larger than the component waves.
Convection - heat transfer by means of motion of fluid.
Conventional current - motion of positive electrical current.
Converging lens - lens that causes light rays to converge; usually a convex lens.
Convex lens -lens that is thicker in the center than at edges.
Convex mirror - diverging mirror. Center of curvature is on side opposite reflecting side of mirror.
Cosine - the ratio of the adjacent side to the hypotenuse.
Coulomb - unit of electrical charge. Charge caused by flow of one ampere for one second.
Crest of wave - high point of wave motion.
Critical angle - minimum angle of incidence that produces total internal reflection.
Crystal lattice - structure of solid consisting of regular arrangment of atoms.


D

De Broglie wavelength - length of de Broglie wave of particle; Planck’s constant divided by momentum of particle.
Decibel - unit of sound level.
Dependent variable - variable that responds to change in manipulated variable.
Derived units -unit of quantity that consists of combination of fundamental units.
Destructive interference - superposition of waves resulting in a combined wave with zero amplitude.
Diffraction - bending of waves around object in their path.
Diffraction grating - material containing many parallel lines very closely spaced that produces a light spectrum by interference.
Diffuse reflection -reflection of light into many directions by rough object.
Dimensional analysis - checking a derived equation by making sure dimensions are the same on both sides.
Diode - electrical device permitting only one way current flow.
Dispersion of light - variation with wavelength of speed of light through matter resulting in separation of light into spectrum.
Displacement - change in position. A vector quantity.
Dissonance - two or more sounds that, when together, sound unpleasant.
Distance - separation between two points. A scalar quantity.
Diverging lens - lens that causes light rays to spread apart or diverge; usually a concave lens.
Dopants - small quantities of material added to semiconductor to increase electrical conduction.
Doppler shift - change in wavelength due to relative motion of source and detector.
Dynamics - study of motion of particles acted on by forces.

E

Effective current - DC current that would produce the same heating effects.
Effective voltage - DC potential difference that would produce the same heating effects.
Efficiency - ratio of output work to input work.
Effort force - force extended on a machine.
Elastic collision - interaction between two objects in which the total energy is the same before and after the interaction.
Elasticity - ability of object to original shape after deforming forces are removed.
Electrical charge pump - device, often a battery or generator, that increase potential of electrical charge.
Electrical circuit - continuous path through which electrical charges can flow.
Electrical current - flow of charged particles.
Electrical field - property of space around a charged object that causes forces on other charged objects.
Electric field lines - lines representing the direction of electric field.
Electric field strength - ratio of force exerted by field on a tiny test charge to that change.
Electric generator - device converting mechanical energy into electrical energy.
Electric potential - ratio of electric potential energy to charge.
Electric potential difference - difference in electric potential between two points.
Electric potential energy - energy of a charged body in an electrical field.
Electromagnet - device that uses an electric current to produce a concentrated magnetic field.
Electromagnetic force - one of fundamental forces due to electric charges, both static and moving.
Electromagnetic induction - production of electric field or current due to change in magnetic flux.
Electromagnetic radiation - energy carried by electromagnetic waves throughout space.
Electromagnetic waves - wave consisting of oscillating electric and magnetic fields that move at speed of light through space.
Electromotive force - potential difference produced by electromagnetic induction.
Electron - subatomic particle of small mass and negative charge found in every atom.
Electron cloud - region of high probability of finding an electron around an atom.
Electron diffraction - effects on electrons due to wave-like interference of electrons with matter.
Electron gas model - description of current flow through conductors.
Electroscope - device to detect electric charges.
Electrostatics - study of properties and results of electric charges at rest.
Electroweak force - unification of electromagnetic and weak forces.
Elementary charge - magnitude of the charge of an electron. 1.602 *10^ -19
Emission spectrum - spectrum produced by radiation from excited atoms.
Energy - non-material property capable of causing changes in matter.
Energy levels - amounts of energy an electron in an atom may have.
Entropy - measure of disorder in a system; ratio of heat added to temperature.
Equilibrant force - force needed to bring an object into transitional equilibrium.
Equilibrium - condition in which net force is equal to zero. Condition in which net torque on object is zero.
Equivalent resistance - single resistance that could replace several resistors.
Evaporation - change from liquid to vapor state.
Excited state - energy level of atom higher than ground state.
External forces - forces exerted from outside a system.
Extrinsic semiconductor - semiconductor in which conduction is primarily the result of added impurities.


F

Factor-label method - dimensional analysis.
Farad - unit of capacitance. One coulomb per volt.
Ferromagnetic materials - materials in which large internal magnetic fields are generated by cooperative action of electrons.
First harmonic - in music, the fundamental frequency.
First law of thermodynamics - change in internal or thermal energy is equal to heat added and work done on system. Same as law of conservation of energy.
Fluid - material that flows, i.e. liquids, gases, and plasmas.
Focal length - distance from the focal point to the center of a lens or vertex of a mirror.
Focal point - location at which rays parallel to the optical axis of an ideal mirror or lens converge to a point.
Forbidden gap - energy values that electrons in a semiconductor or insulator may not have.
Force - agent that results in accelerating or deforming an object.
Frame of reference -coordinate system used to define motion.
Fraunhofer lines - absorption lines in the sun’s spectrum due to gases in the solar atmosphere.
Frequency - number of occurrences per unit time.
Friction - force opposing relative motion of two objects are in contact.
Fundamental particles - those particles( i.e. quarks and leptons) of which all materials are composed.
Fundamental tone - lowest frequency sound produced by a musical instrument.
Fundamental units - set of units on which a measurement system is based( i.e. meter, second, kilogram, ampere, candela).
Fuse - metal safety device in an electric circuit that melts to stop current flow when current is too large.
Fusion - combination of two nuclei into one with release of energy.
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G -
Galvanometer - device used to measure very small currents.
Gamma decay - process by which a nucleus emits a gamma ray.
Gamma particle - high energy photon emitted by a radioactive nucleus.
Gas - state of matter that expands to fill container.
Geiger-Mueller tube - device used to detect radiation using its ability to ionize matter.
General theory of relativity - explanation of gravity and accelerated motion invented by Einstein.
Gluon - carrier of strong nuclear force.
Grand unified theories - theories being developed that unify the stronger and electroweak forces into one force.
Gravitational field - distortion of space due to the presence of mass.
Gravitational force - attraction between two objects due to their mass.
Gravitational mass - ratio of gravitational force to object’s acceleration.
Gravitational potential energy - change of energy of object when moved in a gravitational field.
Graviton - particle that carries the gravitational force. Not yet observed.
Ground state - lowest energy level of an electron in an atom.
Grounding - process of connecting a charged object to Earth to remove object’s unbalanced charge.
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H -
Half-life - length of time for half of a sample of radioactive material to decay.
Harmonics - frequencies produced by musical instrument that are multiples of fundamental tone.
Heat - quantity of energy transferred from one object to another because of a difference in temperature.
Heat engine - device that converts thermal energy to mechanical energy.
Heat of fusion - quantity of energy needed to change a unit mass of a substance from solid to liquid state at the melting point.
Heat of vaporization - quantity of energy needed to change a unit mass of a substance from liquid to gaseous state at the boiling point.
Heavy water - deuterium oxide used mainly in CANDU nuclear reactors.
Heisenberg uncertainty principle - the more accurately one determines the position of a particle, the less accurately the momentum can be known, and vice versa.
Hertz - unit of frequency equal to one event or cycle per second.
Hole - absence of an electron in a semiconductor.
Hooke’s law - deformation of an object is proportional to force causing it.
Huygens’ wavelets - model of spreading of waves in which each point on wavefront is source of circular or spherical waves.
Hydraulic system - machines using fluids to transmit energy.
Hyperbola - mathematical curve that describes an inverse relationship between two variables.
Hypotenuse - side opposite the right angle in a triangle.
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I -
Ideal mechanical advantage - in simple machine, the ratio of effort distance to resistance distance.
Illuminance - rate at which electromagnetic wave energy falls on a surface.
Illuminated object - object on which light falls.
Image - reproduction of object formed with lenses or mirrors.
Impulse - product of force and time interval over which it acts.
Impulse-momentum theorem - impulse given to an object is equal to its change in momentum.
Incandescent body - object that emits light because of its high temperature.
Incident wave - wave that strikes a boundary where it is either reflected or refracted.
Incoherent light - light consisting of waves that are not in step.
Independent variable - variable that is manipulated or changed in an experiment.
Index of refraction - ratio of the speed of light in vacuum to its speed in a material.
Inelastic collision - collision in which some of the kinetic energy is changed into another form.
Inertia - tendency of object not to change its motion.
Inertial mass - ratio of net force exerted on object to its acceleration.
Initial velocity - velocity of object at time t=0.
Instantaneous acceleration - acceleration at a specific time; slope of tangent to velocity- time graph.
Instantaneous position - position of an object at specific time.
Instantaneous velocity - slope of the tangent to position- time graph.
Insulator - material through which the flow of electrical charge carriers or heat is greatly reduced.
Interference fringes - pattern of dark and light bands from interference of light waves.
Interference of waves - displacements of two or more waves, producing either large or smaller waves.
Internal forces - forces between objects within a system.
Intrinsic semiconductor - semiconductor in which conduction is by charges due to host material, not impurities.
Inverse relationship - mathematical relationship between two variables, x and y, summarized by the equation xy=k, where k is a constant.
Ionizing radiation - particles or waves that can remove electrons from atoms, molecules, or atoms in a solid.
Isolated system - a collection of objects not acted upon by external forces into which energy neither enters nor leaves.
Isotope - atomic nuclei having same number of protons but different numbers of neutrons.
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J -
Joule - SI unit of energy equal to one Newton-meter.
Joule heating - increase in temperature of electrical conductor due to conversion of electrical to thermal energy.
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K -
Kelvin temperature scale - scale with 0 K= absolute zero and 273.16 K = triple point of water.
Kepler’s laws - three laws of motion of bodies attracted together by the gravitational force.
Kilogram - SI unit of mass.
Kilowatt hour - amount of energy equal to 3.6 * 10^ 6 J. Usually used in electrical measurement.
Kinematics - study of motion of objects without regard to the causes of this motion.
Kinetic energy - energy of object due to its motion.
Kinetic-molecular energy - description of matter as being made up of extremely small particles in constant motion.
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L -
Laser -devise that produces coherent light by stimulated emission of radiation.
Laser- induced fusion - proposed method of creating nuclear fusion by using heating caused by intense laser beams to squeeze matter together.
Law of conservation of energy - in a closed, isolated system, the total momentum is constant.
Law of reflection - angle of incidence of a wave is equal to the angle of reflection.
Law of universal gravitation - gravitational force between two objects depends directly on the product of their masses and inversely on the square of their separation.
Lens - optical device designed to converge or diverge light.
Lens equation - See mirror equation.
Lenz’s law - magnetic field generated by an induced current opposes the change in field that caused the current.
Lepton - particle that interacts with other particles only by the electroweak and gravitational interactions.
Lever arm - component of the displacement of the force from the axis of rotation in the axis of rotation in the direction perpendicular to the force.
Light - electromagnetic radiation with wavelengths between 400 and 700 nm that is visible.
Linear accelerator - device to accelerate subatomic particles by applying successive electric field.
Linear relationship - relationship between two variables, x and y, summarized by the equation y= ax + b, where a and b are constant.
Linear restoring force - force in direction toward equilibrium position that depends linearly on distance from distance from that position.
Liquid - materials that have fixed volume but whose shape depends on the container.
Lodestone - naturally occurring magnetic rock.
Longitudinal waves - wave in which direction of disturbance is the same as the direction of travel of wave.
Loudness - physiological measure of amplitude of a sound wave; heard on pitch and tone colour as well as amplitude.
Lumen - unit of luminous flux.
Luminance intensity - measure of light emitted by source in candelas; luminous flux divided by 4pie.
Luminous flux - flow of light from source measured in lumens.
Luminous object - object that emits light, as opposed to one that reflects light.
Lux - unit of luminous flux; one lumen per square meter.
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M -
Machine - device that changes force needed to do work.
Magnetic field - space around a magnet throughout which magnetic force exists.
Magnification - ratio of size of an optical image to the size of the object.
Manipulated variable - variable that the experimenter can change.
Mass defect - mass equivalent of the binding energy; m=E/c^ 2
Mass number - number of nucleons ( protons plus neutrons) in the nucleus of an atom.
Mass spectrometer - device used to measure the mass of atoms or molecules.
Matter wave - wave-like properties of particles such as electrons.
Mechanical advantage - ratio of resistance force to effort force in a machine.
Mechanical energy - sum of potential and kinetic energy.
Mechanical resonance - condition at which natural oscillation frequency equals frequency of driving force; amplitude of oscillatory motion at a maximum.
Mechanical wave - wave consisting of periodic motion of matter; e.g. sound wave or water wave as opposed to electromagnetic wave.
Melting point - temperature at which substance changes from solid to liquid state.
Meson - medium mass subatomic particle consisting of combination of a quark and antiquark.
Meter - SI unit of length.
Mirror equation - 1/do +1/di=1/f, where do is object distance, di is image distance, f is focal length.
Moderator - material used to decrease speed of neutrons in nuclear reactor.
Momentum - product of object’s mass and velocity.
Monochromatic light - light of a single wavelength.
Mutual inductance - measures the amount of overlap between the magnetic flux produced in one coil and that which passes through a second coil, thus the amount of EMP induced in a secondary coil by the varying flux in the primary coil.
Myopia - defect of eye, commonly called nearsightedness, in which distant objects focus in front of the retina.
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N -
n-type semiconductor - semiconductor in which current is carried by electrons.
Net force - vector sum of forces on object.
Neutral - object that has no net electric charge.
Neutrino - chargeless, massless, subatomic particle emitted with beta particles; type of lepton.
Neutron - subatomic particle with no charge and mass slightly greater than that of proton; type of nucleon.
Newton - SI unit of force.
Newton’s law of motion - laws relating force and acceleration.
Node - point where disturbances caused by two or more waves result in no displacement.
Normal - perpendicular to plane of interest.
Normal force - force perpendicular to surface.
Nuclear equation - equation representing a nuclear reaction.
Nuclear fission - reaction in which large nucleus splits into two parts, often approximately equal in mass.
Nuclear fusion - reaction in which two nuclei are combined into one.
Nuclear reaction - reaction involving the strong force in which the number of protons or neutrons in a nucleus changes.
Nuclear reactor - device in which nuclear fusion is used to generate electricity.
Nuclear transmutation - change of one nucleus into another as the result of a nuclear reaction.
Nucleon - either a proton or a neutron.
Nuclide - nucleus of an isotope.
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O -
Object - source of diverging light rays; either luminous or illuminated.
Octave - interval between two frequencies with a ratio of two to one.
Ohm - SI unit of resistance; one volt per ampere.
Ohm’s law - resistance of object is constant, independent of voltage across it.
Opaque - material that does not transmit light.
Open- pipe resonator - cylindrical tube with both ends closed and a sound source at one end.
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P -
p-type semiconductor - semiconductor in which conduction is the result of motion of holes.
Pair production - formation of particle and antiparticle from gamma rays.
Parabolic mirror - mirror the shape of a paraboloid of revolution that has no spherical aberration.
Parallel circuit - circuit in which there are two or more paths for current flow.
Parallel connection - connection of two or more electrical devices between two points to provide more than one current path.
Pascal - SI unit of pressure; one neutron per square meter.
Pascal’s principle - pressure applied to a fluid is transmitted undiminished throughout it.
Period - time needed to repeat one complete cycle of motion.
Periodic motion - motion that repeats itself at regular intervals of time.
Photoelectric effect - election of electrons from surface of metal exposed to electromagnetic radiation.
Photon - quantum of electromagnetic waves; particle aspect of these waves.
Photovoltaic cell - device that converts electromagnetic radiation into electrical energy.
Physics - study of matter and energy and their relationship.
Piezoelectricity - electric potential produced by deforming material.
Pigment - coloured material that absorbs certain colours and transmits or reflects others.
Pitch - perceived sound characteristics equivalent to frequency.
Planck’s constant - ratio of energy of photon to its frequency.
Plane mirror - flat, smooth surface that reflects light regularly.
Plasma - state of matter in which atoms are separated into electrons and positive ions or bare nuclei.
Point object - object idealized as so small to be located at only one position.
Polarized light - light in which electric fields are all in same plane.
Position - separation between object and a reference point.
Position- time graph - graph of object’s motion that shows how its position depends on clock reading, or time.
Positron - antiparticle equivalent of electron.
Potential difference - difference in electric potential between two points.
Potential energy - energy of object due to its position or state.
Potentiometer - electrical device with variable resistance; rheostat.
Power - rate of doing work; rate of energy conversion.
Precision - degree of exactness in a measurement.
Pressure - force per unit area.
Primary coil - transformer coil that, when connected to voltage source, creates varying magnetic flux.
Primary light colours - red, green, or blue light.
Primary pigment - yellow, green, or magenta light.
Principal axis - line connecting center of curvature of spherical mirror with its geometric vertex. Line perpendicular to plane of lens passing through its center.
Principle of superposition - displacement due to two or more forces is equal to vector sum of forces.
Projectiles - motion of objects given initial velocity that then move only under force of gravity.
Proton - subatomic particle with positive charge that is nucleus of hydrogen atom.
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Q -
quantized - a quantity that cannot be divided into smaller increments forever, for which there exists a minimum, quantum increment.
Quantum mechanic - study of properties of matter using its wave properties.
Quantum model of atom - atomic model in which only probability of locating electron is known.
Quantum number - integer ratio of energy to its quantum increment.
Quark - basic building block of protons, neutrons, other baryons, and mesons.
Quark model - model in which all particles that interact via the strong interaction are composed of two or three quarks.
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R -
Radiation - electromagnetic waves that carry energy.
Radioactive decay - spontaneous change of unstable nuclei into other nuclei.
Radioactive materials - materials that undergo radioactive decay.
Range of projectile - horizontal distance between launch point of projectile and where it returns to launch height.
Ray model of light - light may be represented by straight line along direction of motion.
Ray optics - study of light using ray model.
Rayleigh criterion - two optical images are separable if central bright spot of one image falls on first dark band of second.
Real image - optical image at which rays from object converge.
Receiver - device that detects electromagnetic waves.
Reference level - location at which potential energy is chosen to be zero.
Reference point - zero location in a coordinate system or frame of reference.
Refraction - change in direction of light ray when passing one medium to another.
Refractive index - ratio of speed of light in vacuum to that in the medium.
Resistance - ratio of potential difference across device to current through it.
Resistance force - force exerted by a machine.
Resistor - device designed to have a specific resistance.
Responding variable - variable that changes as result of change in manipulated variable.
Rest energy - energy due to mass of object; E= mc^ 2.
Resultant - vector sum of two or more vectors.
Right -hand rules - used to find force on current or moving particle in magnetic field; used to find direction of magnetic field caused by current or of induced EMF.
Rutherford’s model of atom - nuclear model of atom; essentially all mass in compact, positively- charged object at center, surrounded by electrons.
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S -
Scalar - quantity, like distance, that has only a magnitude, or size.
Schematic diagram - representation of electric circuit using symbols.
Scientific notation - numbers expressed in form M * 10 ^ n , where 1< M < 10, and n is an integer.
Scintillation - flash of light emitted when substance is struck by radiation.
Second - SI unit of time.
Second law of thermodynamics - heat flow only from region of high temperature o region of lower temperature.
Secondary coil - transformer coil in which varying EMF is induced.
Secondary light colours - yellow, cyan, or magenta light.
Secondary pigment - red, green, or blue pigment.
Self- inductance - induced EMF produced in coil by changing current.
Semiconductor - material in which electrical conduction is smaller than that in a conductor, but more than in insulator.
Series circuit - circuit in which electrical current flows through each component, one after another.
Series connection - arrangement of electrical devices so that there is only one path through which current can flow.
Short circuit - low resistance connection between two points, often accidental.
SI - internationally agreed -upon method of using the metric system of measurement.
Significant digit - reliable digits reported in a measurement.
Simple harmonic motion - motion caused by linear restoring that has a period independent of amplitude of motion.
Simple machine - machine consisting of only one lever, inclined plane, wedge, screw, pulley, or wheel and axle.
Sine - the ratio of the opposite side and the hypotenuse.
Sliding friction - force between two surfaces in relative motion.
Slope - ratio of the vertical separation, or rise to the horizontal separation, or run.
Solid - state of matter with fixed volume and shape.
Sound level - quantity measuring logarithm of sound intensity in decibels.
Spark chamber - device used to detect path of charged subatomic particles by a spark that jumps along path of ionization created in a gas.
Specific heat - thermal energy needs to change temperature of unit mass of substance one Kelvin.
Spectroscope - device used to study spectrum of material.
Spectrum - collection of wavelengths in electromagnetic spectrum.
Speed - ratio of distance traveled to time interval.
Speed of light - in vacuum, 2.9979458 * 10^8 m/s.
Spherical aberration - inability of spherical mirror to focus all parallel rays to a single point.
Standing wave - wave with stationary nodes.
Static friction - force that opposes start of motion between two surfaces.
Step- down transformer - transformer with output voltage smaller than input voltage.
Step- up transformer - transformer with output voltage larger than input voltage.
Stimulated emission - emission of photon from excited atom caused by impact fo photon of same energy.
Strong nuclear force - force of very short range that holds neutrons and protons in nucleus together.
Superconductor - electrical conductor that has no resistance and low temperatures.
Surface wave - wave on surface of liquid with characteristics of both longitudinal and transverse waves.
Symmetry - property that is now charged when operation or reference frame is charged.
Synchrotron - device to accelerate particles in which particles move in circular path.
System - defined collection of objects.
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T -
tangent - the ratio of the opposite side and the adjacent side.
Temperature - measure of hotness of object on a quantitative scale. In gases, proportional to average kinetic energy of molecules.
Terminal velocity - velocity of falling object reached when force of air resistance equals weight.
Test charge - charge used, in principle, to measure electric field.
Thermal energy - internal energy. Sum of kinetic and potential energy of random motion of particles making up object.
Thermal equilibrium - state between two or more bodies where temperatures do not change.
Thermal expansion - increase of length or volume of object due to change in temperature.
Thermometer - device used to measure temperature.
Thermonuclear reaction - nuclear fusion.
Thin- film interference - light interference caused by reflection from both front and rear surface of thin layer of liquid or solid.
Timbre - sound quality or tone colour; spectrum of sound frequencies that produce a complete wave.
Time interval - difference in time between two clock readings.
Tokamak - type of fusion reactor.
Tone colour - timbre or tone quality.
Torque - product of force and the lever arm.
Trajectory - the path followed by projectile.
Transformer - device to transform energy from one electrical circuit to another by means of mutual inductance between two coils.
Transistor - semiconductor device that controls large current by means of small voltage changes.
Translucent - material transmitting light without but distorting its path.
Transmutation - nuclear change from one element to another.
Transparent - material transmitting light without distorting directions of waves.
Transverse waves - wave in which disturbance is perpendicular to direction of travel of wave.
Traveling wave - moving, periodic disturbance in a medium or field.
Trigonometry - branch of math that deals with the relationship among angles and sides of triangles.
Trough of wave - low point of wave motion, where displacement is most negative.
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U -
Uniform acceleration - constant acceleration.
Uniform circular motion - motion in a circle of constant radius with constant speed.
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V -
Valence band - in a solid, the range of energies of electrons that are bound to atoms.
Vector quantity - quantity having both magnitude (size) and direction.
Vector resolution - process of finding the effective value of a component in a given direction.
Velocity - ratio of change in position to time interval over which change takes place.
Velocity- time graph - plot of velocity of object as a function of time.
Virtual image - point from which light rays appear to diverge without actually doing so.
Viscous fluid - fluid that creates force that opposes motion of objects through it. The force is proportional to object’s speed.
Volatile liquid - liquid that is easily vaporized.
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W -
Watt - unit of power, one joule per second.
Wavelength - distance between corresponding points on two successive waves.
Wave pulse - single disturbance moving through a medium or field.
Weak boson - particle that carries or transmits the weak interaction of force.
Weak interaction - force involved in beta decay of the neutron and atomic nuclei; one aspect of the electroweak force.
Weight - force of gravity of an object.
Weightlessness - object in freefall, on which only the gravitational force acts.
Wilson cloud chamber - chamber containing supersaturated vapor through which ionizing radiation leaves trails of visible droplets.
Work - product of force and displacement in the direction of the force.
Work function - energy needed to remove an electron from metal.
Work energy theorem - work done on object is equal to the change in its kinetic energy.
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X -
X ray - high- energy photons; high- frequency, short-wavelength electromagnetic waves.
X-ray diffraction - A complicated technique using x-rays to "create an image" where no lense to focus the light rays is available.
X-ray images - Images such as photographs or computer enhanced images produced by bombarding a target with x-rays.
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Y -
Young's modulus - A constant of proportionality associated with the change in length of a material according to its elastic properties.
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Z -
Zero-point energy - The lowest energy state of molecular vibration