"Siemens (unit) The siemens (symbol: S) is the derived unit of electric conductance, electric susceptance and electric admittance in the International System of Units (SI). Conductance, susceptance, and admittance are the reciprocals of resistance, reactance, and impedance respectively; hence one siemens is redundantly equal to the reciprocal of one ohm, and is also referred to as the ""mho"". The 14th General Conference on Weights and Measures approved the addition of the siemens as a derived unit in 1971. The unit is named after Ernst Werner von Siemens. In English, the same form ""siemens"" is used both for the singular and"
"SI unit is the ohm. The statohm is nearly a trillion times larger than the ohm and is the largest unit of resistance ever used in any measurement system. The statohm as a practical unit is as unusably large as the abohm is unusably small. 1 statohm = 8.987551787x10 ohms Statohm The statohm is the unit of electrical resistance in the electrostatic system of units which was part of the CGS system of units based upon the centimetre, gram and second. The static units in that system were related to the equivalent electromagnetic units by a factor of the speed"
"SI unit of resistivity is the Ohm-meter (Ω-m); in the United States the Ohm-centimeter (Ω-cm) is often used instead. One Ω-m is 100 Ω-cm. Sometimes the conductivity, the reciprocal of the resistivity, is quoted instead. A wide range of typical soil resistivity values can be found in literature. Military Handbook 419 (MIL-HDBK-419A) contains reference tables and formulae for the resistance of various patterns of rods and wires buried in soil of known resistivity. Being copyright free, these numbers are widely copied, sometimes without acknowledgement. Because soil quality may vary greatly with depth and over a wide lateral area, estimation of"
"Electrical resistivity and conductivity Electrical resistivity (also known as specific electrical resistance, or volume resistivity) is a fundamental property of a material that quantifies how strongly that material opposes the flow of electric current. A low resistivity indicates a material that readily allows the flow of electric current. Resistivity is commonly represented by the Greek letter ""ρ"" (rho). The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). As an example, if a solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1 Ω, then the resistivity of the material is"
"is the driving consideration. Electrical resistivity and conductivity Electrical resistivity (also known as specific electrical resistance, or volume resistivity) is a fundamental property of a material that quantifies how strongly that material opposes the flow of electric current. A low resistivity indicates a material that readily allows the flow of electric current. Resistivity is commonly represented by the Greek letter ""ρ"" (rho). The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). As an example, if a solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1 Ω, then the resistivity"
"capacitance which affect the relation between voltage and current in alternating current circuits. The ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg Simon Ohm. An ohm is equivalent to a volt per ampere. Since resistors are specified and manufactured over a very large range of values, the derived units of milliohm (1 mΩ = 10 Ω), kilohm (1 kΩ = 10 Ω), and megohm (1 MΩ = 10 Ω) are also in common usage. The total resistance of resistors connected in series is the sum of their individual resistance values. The total resistance of resistors"
"the inverse of the ohm for resistance. The Siemens mercury unit was superseded in 1884. Siemens mercury unit The Siemens mercury unit is an obsolete unit of electrical resistance. It was defined by Werner von Siemens in 1860 as the resistance of a mercury column with a length of one metre and uniform cross-section of held at a temperature of zero degrees Celsius. It is equivalent to approximately 0.953 ohm. Glass tube cross sections are typically irregularly conical rather than perfect cylinders, which presented a problem in constructing precise measuring devices. One could make many tubes and test them for"
"in ohms is numerically equal to the resistivity of the material it is made of in Ω⋅m. Conductivity, σ, is the inverse of resistivity: Conductivity has SI units of ""siemens per metre"" (S/m). For less ideal cases, such as more complicated geometry, or when the current and electric field vary in different parts of the material, it is necessary to use a more general expression in which the resistivity at a particular point is defined as the ratio of the electric field to the density of the current it creates at that point: where in which formula_10 and formula_11 are"
"Siemens mercury unit The Siemens mercury unit is an obsolete unit of electrical resistance. It was defined by Werner von Siemens in 1860 as the resistance of a mercury column with a length of one metre and uniform cross-section of held at a temperature of zero degrees Celsius. It is equivalent to approximately 0.953 ohm. Glass tube cross sections are typically irregularly conical rather than perfect cylinders, which presented a problem in constructing precise measuring devices. One could make many tubes and test them for conical regularity, discarding the least regular ones; their regularity can be measured by inserting a"
"Ohm The ohm (symbol: Ω) is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm. Although several empirically derived standard units for expressing electrical resistance were developed in connection with early telegraphy practice, the British Association for the Advancement of Science proposed a unit derived from existing units of mass, length and time and of a convenient size for practical work as early as 1861. The definition of the ohm was revised several times. Today, the definition of the ohm is expressed from the quantum Hall effect. The ohm is defined as an electrical resistance"
"vowel of the prefixed units kiloohm and megaohm is commonly omitted, producing kilohm and megohm. In alternating current circuits, electrical impedance is also measured in ohms. The siemens (symbol: S) is the SI derived unit of electric conductance and admittance, also known as the mho (ohm spelled backwards, symbol is ℧); it is the reciprocal of resistance in ohms (Ω). The power dissipated by a resistor may be calculated from its resistance, and the voltage or current involved. The formula is a combination of Ohm's Law and Joule's law: where: A linear resistor has a constant resistance value over all"
"Magnetic complex reluctance Magnetic complex reluctance (SI Unit: H) is a measurement of a passive magnetic circuit (or element within that circuit) dependent on sinusoidal magnetomotive force (SI Unit: At·Wb) and sinusoidal magnetic flux (SI Unit: T·m), and this is determined by deriving the ratio of their complex ""effective"" amplitudes.[Ref. 1-3] As seen above, magnetic complex reluctance is a phasor represented as ""uppercase Z mu"" where: The ""lossless"" magnetic reluctance, ""lowercase z mu"", is equal to the absolute value (modulus) of the magnetic complex reluctance. The argument distinguishing the ""lossy"" magnetic complex reluctance from the ""lossless"" magnetic reluctance is equal"
"resistance per unit vehicle weight. While they are all ""specific resistances"", sometimes they are just called ""resistance"" although they are really a coefficient (ratio)or a multiple thereof. If using pounds or kilograms as force units, mass is equal to weight (in earth's gravity a kilogram a mass weighs a kilogram and exerts a kilogram of force) so one could claim that formula_3 is also the force per unit mass in such units. The SI system would use N/tonne (N/T, N/t), which is formula_12 and is force per unit mass, where ""g"" is the acceleration of gravity in SI units (meters"
"Susceptance In electrical engineering, susceptance (""B"") is the imaginary part of admittance, where the real part is conductance. The inverse of admittance is impedance, where the imaginary part is reactance and the real part is resistance. In SI units, susceptance is measured in siemens. Oliver Heaviside first defined this property in June 1887. The general equation defining admittance is given by where, The admittance (formula_2) is the inverse of the impedance (formula_7) or where Note: The susceptance formula_5 is the imaginary part of the admittance formula_2. The magnitude of admittance is given by: Reactance is defined as the imaginary part"
"Resistance. Their objectives were to devise a unit that was of convenient size, part of a complete system for electrical measurements, coherent with the units for energy, stable, reproducible and based on the French metrical system. In the third report of the committee, 1864, the resistance unit is referred to as ""B.A. unit, or Ohmad"". By 1867 the unit is referred to as simply Ohm. The B.A. ohm was intended to be 10 CGS units but owing to an error in calculations the definition was 1.3% too small. The error was significant for preparation of working standards. On September 21,"
"1881 the ""Congrès internationale des électriciens"" (international conference of electricians) defined a ""practical"" unit of Ohm for the resistance, based on CGS units, using a mercury column 1 sq. mm. in cross-section, approximately 104.9 cm in length at 0 °C, similar to the apparatus suggested by Siemens. A ""legal"" ohm, a reproducible standard, was defined by the international conference of electricians at Paris in 1884 as the resistance of a mercury column of specified weight and 106 cm long; this was a compromise value between the B. A. unit (equivalent to 104.7 cm), the Siemens unit (100 cm by definition),"
"Thermal resistance Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance. Absolute thermal resistance is the temperature difference across a structure when a unit of heat energy flows through it in unit time. It is the reciprocal of thermal conductance. The SI units of thermal resistance are kelvins per watt or the equivalent degrees Celsius per watt (the two are the same since the intervals are equal: Δ1 K = Δ1 °C). The thermal resistance of materials is"
"Admittance In electrical engineering, admittance is a measure of how easily a circuit or device will allow a current to flow. It is defined as the reciprocal of impedance. The SI unit of admittance is the siemens (symbol S); the older, synonymous unit is mho, and its symbol is ℧ (an upside-down uppercase omega Ω). Oliver Heaviside coined the term ""admittance"" in December 1887. Admittance is defined as where Resistance is a measure of the opposition of a circuit to the flow of a steady current, while impedance takes into account not only the resistance but also dynamic effects (known"
"Acoustic impedance Acoustic impedance and specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting of an acoustic pressure applied to the system. The SI unit of acoustic impedance is the pascal second per cubic metre () or the rayl per square metre (), while that of specific acoustic impedance is the pascal second per metre () or the rayl. In this article the symbol rayl denotes the MKS rayl. There is a close analogy with electrical impedance, which measures the opposition that a system presents to the electrical flow resulting from an"
"the normalised impedance using the lower case ""z"" is given by Similarly, for normalised admittance The SI unit of impedance is the ohm with the symbol of the upper case Greek letter omega (Ω) and the SI unit for admittance is the siemens with the symbol of an upper case letter S. Normalised impedance and normalised admittance are dimensionless. Actual impedances and admittances must be normalised before using them on a Smith chart. Once the result is obtained it may be de-normalised to obtain the actual result. Using transmission line theory, if a transmission line is terminated in an impedance"
"resistance are dyn·s·cm, pascal seconds per cubic metre (Pa·s/m³) or, for ease of deriving it by pressure (measured in mmHg) and cardiac output (measured in l/min), it can be given in mmHg·min/l. This is numerically equivalent to hybrid resistance units (HRU), also known as Wood units (in honor of Paul Wood, an early pioneer in the field), frequently used by pediatric cardiologists. The conversion between these units is: formula_1 The basic tenet of calculating resistance is that flow is equal to driving pressure divided by resistance. where The systemic vascular resistance can therefore be calculated in units of dyn·s·cm as"
"1 Ω⋅m. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity, and measures a material's ability to conduct an electric current. It is commonly represented by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) or γ (gamma) are also occasionally used. Its SI unit is siemens per metre (S/m). In an ideal case, cross-section and physical composition of the examined material are uniform across the sample, and the electric field and current density are both parallel and constant everywhere. Many resistors and conductors do in fact have a uniform cross section with a uniform"
"of resilience, ""σ"" is the yield strength, ""ε"" is the yield strain, and ""E"" is the Young's modulus. This analysis is not valid for non-linear elastic materials like rubber, for which the approach of area under the curve till elastic limit must be used. Resilience (""U"") is measured in a unit of joule per cubic meter (J·m) in the SI system, ""i.e."" elastical deformation energy per surface of test specimen (merely for gauge-length part). Like the unit of tensile toughness (""U""), the unit of resilience can be easily calculated by using area underneath the stress–strain (""σ""–""ε"") curve, which gives resilience"
"unit of mechanical impedance is the mechanical ohm; in SI units this is N-s/m, or Kg/s. The rotational impedance analogy describes rotating mechanical systems and gives rise to the idea of rotational impedance. The unit of rotational impedance in the SI system is N-m-s/rad. The acoustical impedance analogy gives rise to the idea of acoustic impedance. The unit of acoustic impedance is the acoustic ohm; in SI units this is N-s/m. Mobility analogies, also called the Firestone analogy, are the electrical duals of impedance analogies. That is, the effort variable in the mechanical domain is analogous to current (the flow"
"on this topic. In general, works using the term ""thermal resistance"" are more engineering-oriented, whereas works using the term thermal conductivity are more [pure-]physics-oriented. The following books are representative, but may be easily substituted. Thermal resistance Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance. Absolute thermal resistance is the temperature difference across a structure when a unit of heat energy flows through it in unit time. It is the reciprocal of thermal conductance. The SI units of"
"(). Its symbol is usually , and it may be represented by writing its magnitude and phase in the form . However, cartesian complex number representation is often more powerful for circuit analysis purposes. The reciprocal of impedance is admittance, whose SI unit is the siemens, formerly called mho. The term ""impedance"" was coined by Oliver Heaviside in July 1886. Arthur Kennelly was the first to represent impedance with complex numbers in 1893. In addition to resistance as seen in DC circuits, impedance in AC circuits includes the effects of the induction of voltages in conductors by the magnetic fields"
"y – shunt admittance per unit length l – length of line C – capacitance of line Admittance In electrical engineering, admittance is a measure of how easily a circuit or device will allow a current to flow. It is defined as the reciprocal of impedance. The SI unit of admittance is the siemens (symbol S); the older, synonymous unit is mho, and its symbol is ℧ (an upside-down uppercase omega Ω). Oliver Heaviside coined the term ""admittance"" in December 1887. Admittance is defined as where Resistance is a measure of the opposition of a circuit to the flow of"
"plural. For a conducting element, electrical resistance ""R"" and electrical conductance ""G"" are defined as where ""I"" is the electric current through the object and ""V"" is the voltage (electrical potential difference) across the object. The unit siemens for the conductance ""G"" is defined by where Ω is the ohm, A is the ampere, and V is the volt. For a device with a conductance of one siemens, the electric current through the device will increase by one ampere for every increase of one volt of electric potential difference across the device. The conductance of a resistor with a resistance"
"authority of the Office of Weights and Measures of National Institute of Standards and Technology (NIST), enforced by the individual states. The International System of Units (SI) defines seven base units: length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity. By convention, each of these units are considered to be mutually independent of each other; however, in reality they are interdependent given some definitions contain other base SI Units. All other SI units are derived from the seven base units. Since the base units are the reference points for all measurements taken in SI units, if"
"conversion factors in calculations about electrical quantities. However, the centimeter-gram-second, CGS, units turned out to have impractical sizes for practical measurements. Various artifact standards were proposed as the definition of the unit of resistance. In 1860 Werner Siemens (1816–1892) published a suggestion for a reproducible resistance standard in Poggendorffs Annalen der Physik und Chemie. He proposed a column of pure mercury, of one square millimetre cross section, one metre long: Siemens mercury unit. However, this unit was not coherent with other units. One proposal was to devise a unit based on a mercury column that would be coherent – in"
"(UTS) of AISI 1018 Steel is 440 MN/m. In general, the SI unit of stress is the pascal, where 1 Pa = 1 N/m. In Imperial units, the unit of stress is given as lbf/in² or pounds-force per square inch. This unit is often abbreviated as psi. One thousand psi is abbreviated ksi. A factor of safety is a design criteria that an engineered component or structure must achieve. formula_3, where FS: the factor of safety, R: The applied stress, and UTS: ultimate stress (psi or N/m) Margin of Safety is also sometimes used to as design criteria. It is"
"susceptance materials are used in susceptors built into microwavable food packaging for their ability to convert microwave radiation into heat. Susceptance In electrical engineering, susceptance (""B"") is the imaginary part of admittance, where the real part is conductance. The inverse of admittance is impedance, where the imaginary part is reactance and the real part is resistance. In SI units, susceptance is measured in siemens. Oliver Heaviside first defined this property in June 1887. The general equation defining admittance is given by where, The admittance (formula_2) is the inverse of the impedance (formula_7) or where Note: The susceptance formula_5 is the"
"SI base unit The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units and their physical quantities are the meter for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance. The SI base units form a set of mutually independent dimensions as required by dimensional analysis commonly employed in science and technology. The names and symbols of SI base"