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A Kelvin bridge, also called a Kelvin double bridge and in some countries a Thomson bridge, is a measuring instrument used to measure unknown electrical resistors below 1 ohm. It is specifically designed to measure resistors that are constructed as four terminal resistors.
The Kelvin water dropper, invented by Scottish scientist William Thomson (Lord Kelvin) in 1867, [1] is a type of electrostatic generator. Kelvin referred to the device as his water-dropping condenser. The apparatus is variously called the Kelvin hydroelectric generator, the Kelvin electrostatic generator, or Lord Kelvin's thunderstorm.
The water generally travels from anode to cathode, but the direction may vary due to the different surface charge that builds up at the water bridge surface, which will generate electrical shear stresses of different signs. The bridge breaks into droplets due to capillary action when the beakers are pulled apart at a critical distance, or the ...
Kelvin bridge; Kelvin sensing; ... the year of Lord Kelvin's birth, used −267 as an estimate of the absolute zero temperature. ... Thomson's water dropper ...
The kelvin was formally added to the International System of Units in 1954, defining 273.16 K to be the triple point of water. The Celsius, Fahrenheit , and Rankine scales were redefined in terms of the Kelvin scale using this definition.
There are two main theories to explain the effect: the interfacial tension or 'water bridge' theory, [4] and the electrostatic theory. The water bridge theory assumes a three phase system, the particles contain the third phase which is another liquid (e.g. water) immiscible with the main phase liquid (e.g. oil).
With this type of meter, any voltage drop due to the resistance of the first pair of leads and their contact resistances is ignored by the meter. This four terminal measurement technique is called Kelvin sensing, after William Thomson, Lord Kelvin, who invented the Kelvin bridge in 1861 to measure very low resistances. The Four-terminal sensing ...
Before 2019, the triple point of water was used to define the kelvin, the base unit of thermodynamic temperature in the International System of Units (SI). [3] The kelvin was defined so that the triple point of water is exactly 273.16 K, but that changed with the 2019 revision of the SI, where the kelvin was redefined so that the Boltzmann ...