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  2. Vacuum permittivity - Wikipedia

    en.wikipedia.org/wiki/Vacuum_permittivity

    Vacuum permittivity, commonly denoted ε0 (pronounced "epsilon nought" or "epsilon zero"), is the value of the absolute dielectric permittivity of classical vacuum. It may also be referred to as the permittivity of free space, the electric constant, or the distributed capacitance of the vacuum. It is an ideal (baseline) physical constant.

  3. Impedance of free space - Wikipedia

    en.wikipedia.org/wiki/Impedance_of_free_space

    μ 0 ≈ 12.566 × 10 −7 H/m is the magnetic constant, also known as the permeability of free space, ε 0 ≈ 8.854 × 10 −12 F/m is the electric constant, also known as the permittivity of free space, c is the speed of light in free space, [9] [10] The reciprocal of Z 0 is sometimes referred to as the admittance of free space and ...

  4. No such thing as a free lunch - Wikipedia

    en.wikipedia.org/wiki/No_such_thing_as_a_free_lunch

    TANSTAAFL: a plan for a new economic world order. (Pierre Dos Utt, 1949) The earliest known occurrence of the full phrase (except for the "a"), in the form "There ain't no such thing as free lunch", appears as the punchline of a joke related in an article in the El Paso Herald-Post of June 27, 1938 (and other Scripps-Howard newspapers about the same time), entitled "Economics in Eight Words".

  5. Voltage - Wikipedia

    en.wikipedia.org/wiki/Voltage

    Voltage, also known as (electrical) potential difference, electric pressure, or electric tension is the difference in electric potential between two points. [ 1][ 2] In a static electric field, it corresponds to the work needed per unit of charge to move a positive test charge from the first point to the second point.

  6. Inductive charging - Wikipedia

    en.wikipedia.org/wiki/Inductive_charging

    Inductive charging. The primary coil in the charger induces a current in the secondary coil in the device being charged. Inductive charging (also known as wireless charging or cordless charging) is a type of wireless power transfer. It uses electromagnetic induction to provide electricity to portable devices. Inductive charging is also used in ...

  7. Charge carrier - Wikipedia

    en.wikipedia.org/wiki/Charge_carrier

    In solid state physics, a charge carrier is a particle or quasiparticle that is free to move, carrying an electric charge, especially the particles that carry electric charges in electrical conductors. [ 1] Examples are electrons, ions and holes. [ 2] In a conducting medium, an electric field can exert force on these free particles, causing a ...

  8. Free and open-source software - Wikipedia

    en.wikipedia.org/wiki/Free_and_open-source_software

    Free and open-source software ( FOSS) is software that is available under a license that grants the right to use, modify, and distribute the software, modified or not, to everyone free of charge. The public availability of the source code is, therefore, a necessary but not sufficient condition. FOSS is an inclusive umbrella term for free ...

  9. Freemium - Wikipedia

    en.wikipedia.org/wiki/Freemium

    In the freemium business model, business tiers start with a "free" tier. Freemium, a portmanteau of the words "free" and "premium", is a pricing strategy by which a basic product or service is provided free of charge, but money (a premium) is charged for additional features, services, or virtual (online) or physical (offline) goods that expand the functionality of the free version of the software.