Current Electricity - Result Question 43

45. The rate of increase of thermo-e.m.f. with temperature at the neutral temperature of a thermocouple

[2011]

(a) is positive

(b) is zero

(c) depends upon the choice of the two materials of the thermocouple

(d) is negative

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Answer:

Correct Answer: 45. (b)

Solution:

  1. (b) We have, $e=at+bt^{2}$

$\Rightarrow \frac{de}{dt}=a+2 bt$

At neutral temperature,

$t=-\frac{a}{2 b}$

$\therefore \frac{de}{dt}=0$