Reciprocal ohm

The power factor of a sample is determined from the capacitance and resistance values by means of the following relationship, where P = power factor, G = conductance in mhos (reciprocal ohms), W = x. frequency, and C = capacitance. 

Conductance (G,g) is the reciprocal of resistance and has units of reciprocal ohms or mhos (fi" ) or more properly in SI units, seimens. 

The reciprocal of the resistance is termed the conductance (G) this is measured in reciprocal ohms (or Q-1), for which the name siemens (S) is used. The resistance of a sample of homogeneous material, length l, and cross-section area a, is given by ... 

The phenomenon of transmitting electrons through a body (an electric current). Usually associated with the measurement of electrical conductivity through water and measured in micro Siemens per centimeter (p,S/cm) or micromho per centimeter ( xmho/cm). 1 p,S/cm = 1 xmho/cm. The mho is equivalent to a reciprocal ohm (the unit of resistivity). 

The quantity 1/R is a measure of conducting power this quantity is called the conductance. Whilst resistances are usually expressed in ohms, conductances are quoted in reciprocal ohms or mhos. The resistance, R, of any conductor of length L and area of cross-section A is given by... 

In the above relationship p is an intrinsic property called the specific resistance (or resistivity) of the conductor. The definition of the specific resistance of any given conductor follows from this relationship. It is the resistance in ohms of a specimen of the material, 1 cm long and 1 cm2 in cross-sectional area (units ohm cm-1), the length being in the direction of the current and the cross-section normal to it. In other words, the specific resistance p of a conductor is the resistance of a cube of 1 centimeter edge. If the conductance is denoted by C = 1 /R, then the specific conductance (or conductivity) K, is given by JC= 1/a (units ohm-1 cm-1, mho cm-1, reciprocal ohm cm-1). Therefore, the relationship R = aL/A may be written as R = L/KA (units ohms) and the conductance can be expressed as C = 1/R = KA/l (units reciprocal ohms). 

The conductance of an electrolyte solution characterizes the easiness of electric conduction its unit is reciprocal ohm, = siemens = S = A/V. The electric conductivity is proportional to the cross-section area and inversely proportional to the length of the conductor. The unit of conductivity is S/m. The conductivity of an electrol3de solution depends on the concentration of the ions. Molar conductivity, denoted as X, is when the concentration of the hypothetical ideal solution is 1 M = 1000 mol/m. Hence, the unit of molar conductivity is either Sm M , or using SI units, Sm mol . For nonideal solutions, X depends on concentration, and the value of X at infinite dilution is denoted by subscript "0" (such as >,+ 0, and X for cation and anion molar conductivity). The conductivity is a directly measurable property. The molar conductivity at infinite dilution may be related to the mobility as follows ... 

The tinctura iodi of the British Pharmacopoeia is a soln. of half an ounce of iodine, and a quarter of an ounce of potassium iodide in a pint of rectified spirit. P. Wantig found the mol. ht. of soln. —1 941 Cals., and S. U. Pickering —1 714 per 880 mol. of ethyl alcohol. C. Lowig found that alcoholic tincture of bromine is slowly decomposed in darkness, rapidly in light. Alcoholic soln. of iodine, according to H. E. Barnard, are stable in light and in darkness, but according to J. M. Eder they decompose 1000 times more slowly than chlorine water under similar conditions T. Budde has shown that hydriodic acid, acetic ester, and aldehyde are formed, and the electrical conductivity of the soln. increases. J. H. Mathews and E. H. Archibald and W. A. Patrick found a freshly prepared AT-soln. to have an electrical conductivity of 2 4 XlO-6 reciprocal ohms and a sat. soln., 1 61 X10 4 reciprocal ohms at 25°. The decomposition is accelerated by the presence of platinum. The heat of soln. decreases with concentration from —7 92 to —7 42 cals, respectively for dilute and sat. soln. in methyl alcohol, and likewise from —4 88 to —5 22 cals, for similar soln. in ethyl alcohol. The solubility of iodine in aq. soln. of propyl alcohol is not very different from that in ethyl alcohol. 

The specific electrical conductivity 3 K of soln. of potassium iodide and of similar soln. sat. with iodine expressed in reciprocal ohms is for soln. containing n milligram molecules per litre... 

Potassium and sodium are good conductors of heat.23 If the conductivity of silver be unity, that of sodium is 0 365. J. W. Hornbeck found the temp, coeff. of the thermal conductivity of potassium or sodium falls with rise of temp. The alkali metals are also good conductors of electricity 24 for example, the conductivity of sodium for heat and electricity is exceeded only by silver, copper, and gold. According to E. F. Northrup, the metals sodium, potassium, mercury, tin, lead, and bismuth have the same value for the ratio of the coeff. of electrical resistance to the coeff. of cubical expansion at the same temp. The electrical conductivity of lithium is nearly ll-4xl04 reciprocal ohms at 20°, that is, about 20 4 per cent, of the conductivity of hard silver of sodium at 2T 70, 22 4 XlO4 reciprocal ohms, that is, about 36 5 per cent, of the value of silver. 

P. Walden 39 found that soln. of potassium iodide in liquid sulphur dioxide have an eq. conductivity at 0° of 44 5 reciprocal ohms when a mol. is dissolved in 15 3 litres and of 99 0 in 760 litres—these results are rather smaller than with water. Similar results were obtained with sodium iodide 30 2 with a dilution t =18 6, and 35 1 with i =60. The raising of the b.p. of soln. of sodium iodide in liquid sulphur dioxide gave almost twice the theoretical value for the mol. wt. of Nal. With an ionized salt, the mol. wt. would be less than the theoretical value. 

K is expressed in units of reciprocal ohms (mhos) per centimeter (i.e., ohm-1 cm-1). Methods of measurement, cell selection and use, and the appropriate electrical circuitry are discussed by Shedlovsky (1959). 

Definitions and Units. Electrolytic conductivity is often defined as the electrical conductance of a unit cube of solution as measured between opposite faces. It is expressed in the same units as electrical conductivity, i.e.. reciprocal ohms per unit length. Most commonly wc find Mho/eemimeter (fU cm"1). siemens/cenlimeter IS cm 1), and siemcns/meler (S cnT1) ... 

The electrical conductivity of water at 18°C is 0.04 x 10 reciprocal ohms (measurements of Kohlraush and IfeydweiUer, 1902) of pure water in equilibrium with air, 0.8 x 10-6 of ordinary distilled water, about 5 x 10- . 

The crystalline acid has an appreciable specific conductivity of about 1 x 10 4 reciprocal ohms (mhos), while the fused acid at the same temperature has a conductivity of 1 x 10 2 mhos.4 Specific conductivities of the more concentrated solutions show a maximum at about 43 per cent., as appears from the following data —5... 

The Specific conductance of any conducting material is defined as th( reciprocal of the specific resistance it is given the symbol k and is stated in reciprocal ohm units, sometimes called mhos/ Since, by definition, K is equal to 1/p, it follows from equation (1) that... 

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