Thermocouple

When two dissimilar metals are put into contact with each other, a small voltage in the millivolt range is generated. This junction emf is temperature dependent and can be used as a thermometer. If a loop is made from two lengths of wire of dissimilar metals, and the two junctions placed at different temperatures, a small current will flow around the wire loop. A practical thermometer can be constructed by putting one junction at a standard temperature, say an ice bath, and the other at the temperature to be measured. Iron is often one of the materials used, and a common material with which to pair it is constantan. This combination gives a voltage on the order of 5 millivolts when one junction is at 0 C and the other is at 100 C.

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Junction Emfs

When two dissimilar metals are put into contact with each other, a small voltage in the millivolt range is generated. This junction emf is temperature dependent and can be used as a thermometer by making up a thermocouple from two wires of dissimilar metals.

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