A multimeter can be used to measure resistance in ohms. It can also be used to measure capacitance, voltage, amperage, ect.

Several resistors. Their resistance, in ohms, is marked using a color code.

The ohm (symbol: Ω) is the SI unit of electrical impedance or, in the direct current case, electrical resistance, named after Georg Ohm. Image File history File links Download high-resolution version (1600x1067, 265 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Ampere Volt Ohm ... Image File history File links Download high-resolution version (1600x1067, 265 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Ampere Volt Ohm ... Image File history File links Aeldre_kulmassemodstande. ... Image File history File links Aeldre_kulmassemodstande. ... Resistor symbols (non-European) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... The electronic color code discussed here is used to indicate the values or ratings of electronic components, very commonly for resistors, but also for capacitors, inductors, and others. ... Omega (Ω ω) is the 24th and last letter of the Greek alphabet. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Georg Simon Ohm, (March 16, 1789 Erlangen, Germany - July 6, 1854, Munich) a German physicist, was born in Erlangen and educated at the university there. ...

Definition

An ohm is the electrical resistance offered by a current-carrying element that produces a voltage drop of one volt when a current of one ampere is flowing through it. Josephson junction array chip developed by NIST as a standard volt. ... Current can be measured by a galvanometer, via the deflection of a magnetic needle in the magnetic field created by the current. ...

Explanation

R is one ohm if V = one volt and I = one ampere

By definition from Ohm's Law, a device has a resistance of one ohm if a voltage of one volt causes a current of one ampere to flow (R = V/I). Alternatively and equivalently, a device that dissipates one watt of power with one ampere of current flowing through it has a resistance of one ohm (R = P / I ²). Image File history File links Ohms_law_voltage_source. ... Image File history File links Ohms_law_voltage_source. ... For the phase law, see Ohms Phase Law. ... Look up device in Wiktionary, the free dictionary. ... The watt (symbol: W) is the SI derived unit of power, equal to one joule per second. ...

Since 1990, the ohm has been maintained internationally using the quantum Hall effect, where a conventional value is used for the 'von-Klitzing constant', fixed by the 18th General Conference on Weights and Measures as R_{K-90} = 25812.807 Ω. MCMXC redirects here; for the Enigma album, see MCMXC a. ... The quantum Hall effect is a quantum-mechanical version of the Hall effect, observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall conductance σ takes on the quantized values where e is the elementary charge and h is Plancks constant. ... Klaus von Klitzing, (born June 28, 1943 in German occupied Åšroda Wielkopolska) is a German physicist. ... The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, never GCWM). ...

The complex quantity impedance is a generalisation of resistance. Its real part is resistance and its imaginary part is reactance. Impedance, resistance and reactance all have units of ohms. In mathematics, a complex number is a number of the form where a and b are real numbers, and i is the imaginary unit, with the property i 2 = −1. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ... It has been suggested that Electric reactance be merged into this article or section. ...

The symbol for the ohm is the Greek capital letter omega (Ω). If the Greek letter cannot be used, the word ohm is used instead. The various guides for the use of the International System of Units do not explicitly forbid the elision of the final "o" of some SI prefixes, although there is nothing in them to suggest that it is allowable, either. As a result, one is just about as likely to see "kilohm", "kiloohm" and even "kilo-ohm", and the same holds true for hecto-, micro-, nano-, pico-, femto-, atto-, zepto-, and yocto-. The only other SI unit to suffer from this kind of orthographic uncertainty is the ampere. In the particular case of the ohm, one even sees the "a" prefixes lose that vowel: hence megohm and gigohm. Higher prefixes are rarely used with ohm. In the other direction, milliohms (or millohms) are seen where the resistance of cables, etc., are measured. Omega (Ω ω) (literally, big O) is the 24th and last letter of the Greek alphabet. ... Current can be measured by a galvanometer, via the deflection of a magnetic needle in the magnetic field created by the current. ...

Units of ohms, kilohms (10³ Ω) and megohms (10⁶ Ω) are used in electronic design documentation. On schematic diagrams and parts lists kilohms are abbreviated "K" and megohms are abbreviated "M". Thus, 33 kilohms would be rendered as 33K, and 5.1 megohms would be 5.1M. Another commonly used convention is that the multiplier is used to replace the decimal point, so that 5.1 megohms can also be represented as 5M1. This convention is used because a decimal point can be difficult to see in small or cluttered print. Values less than 1K are rendered either (a) without any symbol, or (b) with an "R", following the number; so 680 ohms can be shown as 680 or 680R. Resistors are usually identified by a reference designator, R, and a cardinal number, e.g., R12.

Conversions

A measurement in ohms is the reciprocal of a measurement in siemens, the SI unit of electrical conductance. Note that 'siemens' is both singular and plural. The non-SI unit, the mho (simply put, ohm written backwards), is equivalent to siemens but is mostly obsolete and rarely used. The siemens (symbol: S) is the SI derived unit of electric conductance. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... Electrical conductance is the reciprocal of electrical resistance. ... In linguistics, grammatical number is a morphological category characterized by the expression of quantity through inflection or agreement. ... Look up Plural in Wiktionary, the free dictionary Plural is a grammatical number, typically referring to more than one of the referent in the real world. ... The siemens (symbol: S) is an SI derived unit of measurement for electric conductance, being the inverse of the ohm (Ω), named after Werner von Siemens. ...

See also

• Ohm's law
• Resistor
• abohm

For the phase law, see Ohms Phase Law. ... Resistor symbols (non-European) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... The abohm is the basic unit of electrical resistance in the centimeter gram second system of units. ...

External links

• Scanned books of Georg Simon Ohm at the library of the University of Applied Sciences Nuremberg
• Official SI brochure
• NIST Special Publication 811
• History of the ohm at sizes.com