One junction of a certain thermoelectric couple is at a fixed temperature $T_{\mathit{r}}$, and the other junction is at temperature $\mathit{\text{T}}$. The thermo-electromotive force for this is expressed by$\mathit{\text{E}}=\mathit{\text{K}}\left(\mathit{\text{T}}-{\mathit{\text{T}}}_{\mathit{\text{r}}}\right)\left[{\mathit{\text{T}}}_0-\frac{1}{2}(\mathit{\text{T}}+{\mathit{\text{T}}}_{\mathit{\text{r}}}\text{)}\right]$. At temperature $\mathit{\text{T}}=\frac{1}{2}{\mathit{\text{T}}}_0$, the thermoelectric power is,