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

Options

A. `1400^(@) C`
B. `350^(@) C`
C. `700^(@) C`
D. No neutral temperature is possible for this termocouple.

Answer

D

Explanation

Neutral temperature is the temperature of a hot junction at which E is maximum.
`rArr (dE)/( d theta) = 0` or `a + 2b theta=0 rArr theta = (-a)/( 2 b) = - 350`
`rArr (d^(2) E)/( d theta^(2) )= 2 b`
hence no `theta` is possible for E to be maximum no neutral temperature is possible.