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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

The correct Answer is:
D
`E=a theta+btheta^(2)`
For neutral temperature `(theta_(n)), (dE)/(d theta)=0`
`impliesa+2btheta_(n)=0impliestheta_(n)=-a/(2b)`
`:. theta_(n)=-700/2 (`:'`a/b=700^(@)C)`
`=-350^(@)Clt0^(@)C`
But neutral temperature can nerve be negative (less than zero) i.e. `theta_(n)cancellt0^(@)C`. Hence, no. neutral temperature is possible for this thermocouple.
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