Question

The thermo emf E (in volts) of a certain thermocouple is found to vary with Q (in C) according to equation $(E=20Q-\frac{Q^2}{20}$, where Q is temperature of the hot function, the cold function being kept at 0${}^o$C. Then, the neutral temperature of the thermocouple is

• A. 300${}^o$C
• B. 400${}^o$C
• C. 100${}^o$C
• D. 200${}^o$C

Answer 1

The correct option is D 200${}^o$C

Given, thermo emf $E=20Q-\frac{Q^2}{20}$

For neutral temperature, the thermo emf will be maximum so $\frac{dE}{dQ}=0$

or $20-2Q/20=0$ or $Q_n=Q={200}^{o}C$