The thermo e.m.f E in volts of a certain thermocouple is found to very with temperature difference `theta` in `""^(@)C` between the two junctions according to the relation `E = 30 theta - (theta^(2))/(15)` . The neutral temperatur e for the thermo - couple will be .

Options

A. `30^(@) C`
B. `450^(@) C`
C. `400^(@) C`
D. `225^(@) C`

Answer

D

Explanation

`E= 30theta - (theta^(2) )/( 15)`
For neutral temperature, `( dE)/( d theta)= 0`
`0 = 30 - (2)/(15)theta " "theta=15 xx 15= 225^(@) C`
Hence, neutral temperature is 225°C.