Explain variation of thermo e.m.f. with temperature.

Explain variation of thermo e.m.f. with temperature. 
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For a given thermocouple , the temperature of one junction is placed at 00C and temperature of other junction is increased by providing heat. The emf generated is measured with the help of millivoltmeter. Emfs e1, e2, e3,……for different temperatures t1, t2, t3,…… are recorded and the graph is plotted. It is observed that as the temperature difference between two junctions increases, emf also increases and reaches to maximum value and thereafter emf decreases, becomes zero and reverses its sign.

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