It is desired to make a 20Omegacoil of wire with zero thermal coefficient of resistance. To do this a carbon resistor of resistance R_1 is placed in series with an iron resistor of resistance R_2 . The proportions of iron and carbon are so chosen that R_1+ R_2 = 20 Omega at all temperatures near 20^@C. How large are R_1 and R_2? [alpha_c = - 7.5xx10^(2)""^@ C^(-1) and alpha_(Fe) = 5.0xx10^3 ""^@C^(-1) ?

It is desired to make a 20Omegacoil of wire with zero thermal coeffici

1.	It is desired to make a 20Omegacoil of wire with zero thermal coefficient of resistance. To do this a carbon resistor of resistance R_1 is placed in series with an iron resistor of resistance R_2 . The proportions of iron and carbon are so chosen that R_1+ R_2 = 20 Omega at all temperatures near 20^@C. How large are R_1 and R_2? [alpha_c = - 7.5xx10^(2)""^@ C^(-1) and alpha_(Fe) = 5.0xx10^3 ""^@C^(-1) ?
Answer» SOLUTION :`R_1 = 1.25 OMEGA and R_2 = 18.75 Omega`

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