--- title: "Glossary of physics" chunk: 7/13 source: "https://en.wikipedia.org/wiki/Glossary_of_physics" category: "reference" tags: "science, encyclopedia" date_saved: "2026-05-05T07:51:11.278375+00:00" instance: "kb-cron" --- electrical insulator Also simply insulator. Any material whose internal electric charges do not flow freely and which therefore does not readily conduct an electric current under the influence of an electric field. electrical potential energy electrical and electronics engineering electrical network An interconnection of electrical elements such as resistors, inductors, capacitors, voltage sources, current sources, and switches. electrical resistance Also simply resistance. The opposition to the passage of an electric current through an electrical element. Good insulators typically have very high electrical resistance. electricity The set of physical phenomena associated with the presence and flow of electric charges. electro-optic effect electrochemical cell electrodynamics electrolytic cell electromagnet A type of magnet in which the magnetic field is produced by the flow of an electric current. electromagnetic field Also abbreviated EM field or EMF. A physical field produced by moving electrically charged objects. electromagnetic induction electromagnetic radiation Also abbreviated EM radiation or EMR. A form of energy emitted and absorbed by charged particles, which exhibits wave-like behavior as it travels through space. electromagnetic spectrum electromagnetic wave equation electromagnetism electromechanics electromotive force ( E {\displaystyle {\mathcal {E}}} ) Also abbreviated emf. The electrical intensity or "pressure" developed by a source of electrical energy such as a battery or generator and measured in volts. Any device that converts other forms of energy into electrical energy provides electromotive force as its output. electron A subatomic particle with a negative elementary electric charge. electron capture electron cloud electron pair electron paramagnetic resonance Also called electron spin resonance (ESR) and electron magnetic resonance (EMR). A method for studying materials with unpaired electrons which makes use of the Zeeman effect. It shares some basic principles with nuclear magnetic resonance (NMR). electronvolt (eV) A unit of energy equal to approximately 1.6×10−19 joule. By definition, it is the amount of energy gained by the charge of a single electron moved across an electric potential difference of one volt. electronegativity A chemical property that describes the tendency of an atom or a functional group to attract electrons (or electron density) towards itself. electronics A field that deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes, and integrated circuits as well as associated passive interconnection technologies. electrostatics electrostriction elementary charge elementary particle emission spectrum emissivity energy The ability to do work. energy level endothermic An adjective used to refer to a process or reaction in which a system absorbs energy from its surroundings, usually in the form of heat but also in the form of light, electricity, or sound. Contrast exothermic. engineering physics enthalpy entropy A quantity which describes the randomness or "disorder" of a substance or system. equilibrant force equipartition escape velocity The velocity at which the kinetic energy plus the gravitational potential energy of an object is zero. It is the speed needed to "escape" from a gravitational field without further propulsion. excited state exothermic An adjective used to refer to a process or reaction that releases energy from a system, usually in the form of heat but also in the form of light, electricity, or sound. Contrast endothermic. experimental physics == F == farad falling bodies Objects that are moving towards a body with greater gravitational influence, such as a planet. faraday Faraday constant Fermat's principle Fermi surface fermion A type of particle that behaves according to Fermi–Dirac statistics, obeys the Pauli exclusion principle, and possesses half-integer spin. Fermions include all quarks and leptons, as well as all composite particles made of an odd number of these (such as all baryons and many atoms and nuclei). Fermions constitute one of two main classes of particles, the other being bosons. ferrimagnetism ferromagnetism field line first law of thermodynamics fission Either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei), often producing free neutrons and photons (in the form of gamma rays) and releasing relatively large amounts of energy. flavour fluid fluid mechanics fluid physics fluid statics fluorescence flux flux density focal length focus force (F) Any interaction or influence that, unless counterbalanced by other forces, will cause a physical body to change its velocity or shape. A force has both magnitude and direction, making it a vector quantity. The SI unit used to measure force is the newton. force carrier force field frame of reference Fraunhofer lines free body diagram frequency frequency modulation free fall Any motion of a body where its own weight is the only force acting upon it. freezing point The temperature at which a substance changes state from liquid to solid. friction function fundamental forces Also fundamental interactions. fundamental frequency fundamental theorem of calculus fusion A nuclear reaction in which two or more atomic nuclei join together or "fuse" to form a single, heavier nucleus. == G == gamma ray A form of electromagnetic radiation of very high frequency and therefore very high energy. gas general relativity geophysics gluon Graham's law of diffusion gravitation Also gravity. A natural phenomenon by which physical bodies attract each other with a force proportional to their masses. gravitational constant (G) Also universal gravitational constant and Newton's constant. A physical constant involved in the calculation of the gravitational force between two bodies. gravitational energy The potential energy associated with a gravitational field. gravitational field A model used to explain the influence that a massive body extends into the space around itself, producing a force (gravity) capable of interacting with or influencing other nearby physical bodies. Thus, a gravitational field is used to explain and represent gravitational phenomena. It is measured in newtons per kilogram (N/kg). gravitational potential The gravitational potential at a location is equal to the work (energy transferred) per unit mass that is done by the force of gravity to move an object to a fixed reference location. gravitational wave A ripple in the curvature of spacetime that propagates as a wave and is generated in certain gravitational interactions, travelling outward from their source.