Question

The cold junction of thermo couple is maintained $at+{10}^{0}C$. The emf in the couple reverses its direction when the temperature of hot junction is ${510}^0$C. the temperature at which emf reaches peak value is

• A. ${250}^{0}C$
• B. ${260}^{0}C$
• C. ${1020}^{0}C$
• D. ${1000}^{0}C$

Answer 1

Answer: (B)

${260}^{0}C$

on integrating the given relation,
$at+10=0$
we find $\frac{a{t}^2}{2}+10t=0$
$at=-20$
putting these value in equation (1) we find the value of emf $E=-10$
it is mention that emf is reversing it's direction hence it will be positive
${2T}_n=T_i+T_c$
${2T}_n=10+510$
$T_n=260C$