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The thermo emf of thermocouple varies wi...

The thermo emf of thermocouple varies with the temperature `theta` of the hot junction as `E = atheta + btheta^2` in volts where the ratio `a//b` is `700^@C`. If the cold junction is kept at `0^@C`, then the neutral temperature is

A

`700^@C`

B

`350^@C`

C

`1400^@C`

D

no neutral temperature is possible for this thermocouple

Text Solution

Verified by Experts

`E=a theta+b theta^2` (given)
For neutral temperature `theta_n, (dE)/(d theta)=0 implies a+2 theta_a=0`
or `theta_n=-a/(2b) theta_n=-700/2 [ because a/b=700^@C]`
But neutral temperature can never be negative (less than zero) i.e., `theta, 0^@C`
Hence, no neutral temperature is possible for this thermocouple.
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