Ohm's law

Ohm's law
the law that for any circuit the electric current is directly proportional to the voltage and is inversely proportional to the resistance.
[1840-50; named after G. S. OHM]

* * *

Relationship between the potential difference (voltage), electric current, and resistance in an electric circuit.

In 1827 Georg Simon Ohm discovered that at constant temperature, the current I in a circuit is directly proportional to the potential difference V, and inversely proportional to the resistance R, or I = V/R. Resistance is generally measured in ohms (Ω). Ohm's law may also be expressed in terms of the electromotive force E of an electric energy source, such as a battery, or E = IR. In an alternating-current circuit, when the combination of resistance and reactance, called impedance Z, is constant, Ohm's law is applicable and V/I = Z.

* * *

      in electricity, experimentally discovered relationship that the amount of steady current through a large number of materials is directly proportional to the potential difference, or voltage (volt), across the materials. Thus, if the voltage V (in units of volts) between two ends of a wire made from one of these materials is tripled, the current (electric current) I (amperes) also triples; and the quotient V/I remains constant. The quotient V/I for a given piece of material is called its resistance, R, measured in units named ohms. The resistance of materials for which Ohm's law is valid does not change over enormous ranges of voltage and current. Ohm's law may be expressed mathematically as V/I = R. That the resistance, or the ratio of voltage to current, for all or part of an electric circuit at a fixed temperature is generally constant had been established by 1827 as a result of the investigations of the German physicist Georg Simon Ohm.

      Alternate statements of Ohm's law are that the current I in a conductor equals the potential difference V across the conductor divided by the resistance of the conductor, or simply I = V/R, and that the potential difference across a conductor equals the product of the current in the conductor and its resistance, V = IR. In a circuit in which the potential difference, or voltage, is constant, the current may be decreased by adding more resistance or increased by removing some resistance. Ohm's law may also be expressed in terms of the electromotive force, or voltage, E, of the source of electric energy, such as a battery. For example, I = E/R.

      With modifications, Ohm's law also applies to alternating-current circuits, in which the relation between the voltage and the current is more complicated than for direct currents. Precisely because the current is varying, besides resistance, other forms of opposition to the current arise, called reactance. The combination of resistance and reactance is called impedance (electrical impedance), Z. When the impedance, equivalent to the ratio of voltage to current, in an alternating current circuit is constant, a common occurrence, Ohm's law is applicable. For example, V/I = Z.

      With further modifications Ohm's law has been extended to the constant ratio of the magnetomotive force to the magnetic flux in a magnetic circuit (q.v.).

* * *


Universalium. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Ohm's law — Ohm Ohm ([=o]m), n. [So called from the German electrician, G. S. Ohm.] (Elec.) The standard unit in the measure of electrical resistance, being the resistance of a circuit in which a potential difference of one volt produces a current of one… …   The Collaborative International Dictionary of English

  • Ohm's law — n. [see OHM] Elec. a law which states that the current in a DC circuit is directly proportional to the applied voltage and inversely proportional to the resistance …   English World dictionary

  • Ohm's law — ōmz n a law in electricity: the strength or intensity of an unvarying electric current is directly proportional to the electromotive force and inversely proportional to the resistance of the circuit * * * the strength of an electric current… …   Medical dictionary

  • Ohm's law — This article is about the law related to electricity. For other uses, see Ohm s acoustic law. V, I, and R, the parameters of Ohm s law. Ohm s law states that the current through a conductor between two points is directly proportional to the… …   Wikipedia

  • Ohm's law — Ohmo dėsnis statusas T sritis automatika atitikmenys: angl. Ohm s law vok. Ohmsches Gesetz, n rus. закон Ома, m pranc. loi d Ohm, f ryšiai: sinonimas – Omo dėsnis …   Automatikos terminų žodynas

  • Ohm’s law — Omo dėsnis statusas T sritis fizika atitikmenys: angl. Ohm’s law vok. Ohmsches Gesetz, n rus. закон Ома, m pranc. loi d’Ohm, f …   Fizikos terminų žodynas

  • Ohm’s law of acoustics — akustinis Omo dėsnis statusas T sritis fizika atitikmenys: angl. Ohm’s law of acoustics vok. akustisches Ohmsches Gesetz, n rus. закон Ома в акустике, m pranc. loi d’Ohm de l’acoustique, f …   Fizikos terminų žodynas

  • Ohm's law — /ˈoʊmz lɔ / (say ohmz law) noun the law which states that in any electric resistance the current flowing is proportional to the voltage and inversely proportional to the resistance. {See ohm} …  

  • Ohm's law — n. Electr. a law stating that current is proportional to voltage and inversely proportional to resistance. Etymology: see OHM …   Useful english dictionary

  • Ohm's Law —   In a given electrical circuit, the amount of current in amperes (i) is equal to the pressure in volts (V) divided by the resistance, in ohms (R).   ***   In a given electrical circuit, the amount of current in amperes is equal to the pressure… …   Energy terms

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”