Ohms per volt

Since the resistance in the circuit containing the reference electrode is approximately 10,000 ohms, an accurate measure of the cathode-reference electrode potential can only be obtained by the use of a potential measuring device with an imput impedance of at least 100,000 ohms. Although a vacuum-tube voltmeter (VTVM, typical imput impedance 11 x 10 ohms) is suitable for this purpose, a common multimeter (VOM, typical imput impedance 20,000 ohms per volt) is not a satisfactory alternative. 

Sensitivity is a ratio of the response of a measuring device (meter) to the magnitude of the measured quantity (volts, ohms, amperes, etc.). Voltage-measuring devices are rated in ohms per volt (i2 ). On any particular range, it is obtained by dividing the resistance of the instru-... 

If you ever have to work on a power supply, for safety s sake you should discharge all capacitors within it. To do this, connect a resistor across the leads of the capacitor with a rating of three watts or more and a resistance of 100 ohms (Cl) per volt. For example, to discharge a 225-volt capacitor, you would use a 22.5kf2 resistor (225 volts times lOOQ = 22500Q or 22.5 kO). 

For one minute, one horsepower will lift 33,000 pounds one foot, or as a unit of power, this equals a rate of 33,000 foot-pounds of work per minute, or 550 foot-pounds per second. One horsepower equals 746 watts of power. The resistance to flow of electrical current through a wire or conductor is termed an ohm. One ohm is the amount of resistance in a wire through which one ampere of current flows under one volt of electrical pressure. Useful relationships are ... 

The absolute velocity of any ion in cm. per sec. under a potential gradient of 1 volt per cm. can thus be obtained by dividing the ion conductance in ohms cm. by the value of the faraday in coulombs, i.e., 96,500. Since the velocity is proportional to the potential gradient, as a consequence of the applicability of Ohm s law to electrolytes, the speed of an ion can be evaluated for any desired fall of potential. It should be pointed out that equation (20) gives the ionic velocity at infinite dilution the values decrease with increasing concentration, especially for strong electrolytes. 

The thermistors (Model 101 Al, Victory Engineering Corp.) are about %2 inch in diameter. They have a nominal resistance of 10 ohms at room temperature. The catalyst is applied by coating the thermistor with an adhesive and dipping into the pulverized catalyst. In this setup, the output of the bridge when the air stream contains 1 p.p.m. of ozone is about 0.001 volt, which corresponds to a decrease of 5 ohms in the resistance of the coated thermistor. This, in turn, corresponds to a temperature differential of about 0.001° C. per 1 p.p.m. of ozone between the thermistors. 

The Wien Effect. If, instead of using potentials of the order of one volt per centimeter in the measurement of electrolytic conductance, voltages of several hundred thousand times this are employed, the conductances of solutions of electrolytes are no longer constant but tend to increase with the potential. Under these conditions Ohm s law is evidently no longer valid. This increase of conductance at high potentials is called the Wien effect. The passage of high potentials... 

Volt The potential at a point in an electrostatic field is 1 volt, if 1 Joule of work per coulomb is done against electrical forces when a charge is brought from infinity to a point. A more usable definition is that / volt = / ampere flowing through a resistance of 1 ohm. E = 1 x R. Voltages are measured with voltmeters. 

This eqnivalent circnit takes account of the tnrns ratio between the stator and the rotor if all the rotor resistances and reactance are given in the data as referred to the stator valnes. The circnit can be used with actual quantities such as ohms, amps and volts, or in their per-unit equivalent values which is often more convenient. This approach is customary since it easily corresponds to measurements that can be made in practice when tests are carried out in the factory. 

Units of Measurement. All electrical properties must have an associated defined standard unit to be measurable. To that end, current is measured in amperes, named after Louis Ampere. Potential difference, sometimes called electromotive force, is measured in volts, named after Volta. Resistance is measured in ohms, named after Ohm. Power is measured in watts, named after James Watt. Capacitance is measured in farads, named after Michael Faraday. Inductance is measured in henrys, named after Joseph Henry. Conductance, the reciprocal of resistance, is measured in siemens, named after Ernst W. von Siemens. Frequencies are measured in hertz, or cycles per second, named after Gerhard Hertz. 

In the International system of units (SI), now adopted, the basic electric unit is the ampere, A. This is defined as the current I which, if maintained in two parallel conductors of infinite length and negligible circular cross-section, at a distance of 1 metre apart in a vacuum, would produce a force between the conductors equal to 2x10 newton per metre of length. The other common SI electric units are for quantity of electricity, the coulomb, C = As for electric potential, the volt, V = JA s for resistance, the ohm, 11 = VA" and for capacitance, the farad, F=CV ... 

We may further define these factors. The resistance of I ohm is the resistance offered by 14 45 21 of mercury at o when in the form of a uniform cylinder io6 3 cm. long, having a section, therefore, of practically i sq. mm. The strength of current of i amp. is obtained when i coulomb of electricity, i.e. an amount of electricity capable of depositing o ooiiiS gm. of silver, passes a point in the conductor each second. Finally, when a current of i coul. per second is passing through a column of mercury 106 3 I sq. mm. cross section, the difference of potential at the two ends of the mercury column will be i volt. 

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