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The rate of increase of thermo–e.m.f. with temperature at the neutral temperature of a thermocouple
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- is positive
- is zero
- depends upon the choice of the two materials of the thermocouple
- is negative
Correct Option: B
We have,
e = at + bt²
⇒ de/dt = a + 2bt
At neutral temperature,
t = -(a/2b)
∴ de/dt = 0
