Onsager Reciprocal Relations Describe Coupled Flows

Onsager Reciprocal Relations Describe Coupled Flows 

So far, we have considered a single type of force / and a single type of flow J, related by J = Lf, w herc L = cu (see Equations (18.4) and (18.6)). Now consider a more complex situation, e.g., a material in which a temperature 

But in general, multiple flow processes in a system are not independent they are coupled. The heat flow can affect the electrical current and vice versa. (Such observations were first made by Lord Kelvin in 1854.) So the simplest relationships between two forces and two flows are 

Here are two examples of coupling. Suppose you solder together two different metals to make a junction. If you apply a voltage to drive a current flow, it can cause heating or cooling of the junction. This is called the Peltier effect. But the existence of a reciprocal relation means that if you heat or cool a bimetallic junction instead, an electrical current will flow. This is the principle of operation for thermocouples, which convert temperature changes to electrical signals. 

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Onsager Reciprocal Relations Describe Coupled Flows... 

There are different ways of describing the coupled flow problem in streaming potentials, one is by at Onsager s reciprocity relations and the other is by... 

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