Two resistance R1 and R2 are made of different materials. The temperature coefficient of the material of R1 is α and that of the material of R2 is β . The resistance of the series combination of R2 and R1 does not change with temperature, then the ratio of resistances of the two wires at 0o will be:
R1=R01(1+αΔT)
R2=R02(1−βΔT)
Both are connected in series;
Rseries= R01(1+αΔT)+ R02(1−βΔT)
Rseries= is independent of temperature, si cofficient of temperature will be eqaul to zero,
R01α−R02β=0⟹R01R02=βα