For a copper-iron and a chromel-alumel thermocouple, the plots between thermoelectric emf and the temperature `theta` of the hot junction (when the cold junction is at `0^(@)C`)are found to satisfy approximately the parabola equation `V=alpha theta+(1)/(2)betatheta^(2)` with
`alpha=14muV^(@)C^(-1) beta=-0.04V^(@)C^(-2)` (copper-iron)
`alpha=41muCV^(@)C^(-1),beta=-0.002V^(@)C^(-2)` (chromel-alumel)
Which of the two thermocouples would you use to measure temperature in the range of a about `500^(@)C` to `600^(@)C`?

Explanation

The temperature `theta_(n)` (neutral temperature) corresponding to maximum emf is given by
`(dV)/(dtheta)=0,i.e., alpha+beta theta_(n)=0` or `theta_(n)=-(alpha)/(beta)`
For a copper-iron therm ocouple, `theta_(n)=-(14)/(-0.04).^(@)C=350^(@)C`