- #1

peachtree40

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## Homework Statement

In the interval between the freezing point (ice point) of water and 700.0deg-C, a platinum resistance thermometer is to be used for interpolating temperatures from 0 °C to the melting point of zinc, 692.666

*K*. The temperature, in Celcius or Centigrade, is given by a formula for the variation of the resistance of the thermometer with temperature: R = R,o(1 + A Tc + B Tc^2). Ro, A, and B are constants determined by measurements at the ice point, the steam point, and the melting point of zinc. If R equals 7.85630

*ohms*at the ice point, 65.56082

*ohms*at the steam point, and 233.60848

*ohms*at zinc's melting point, find Ro.[/B]

## Homework Equations

## The Attempt at a Solution

(0, 7.85630) (100, 65.56080) (692.666-273.15, 233.608)

These are three ordered pairs of data for the equation

I found Ro by just plugging in 0 and finding that Ro is 7.85630

I then plugged in the other ordered pairs and used algebra to eliminate A

65.56082=7.8563+7.8563(100A)+7.8563(10000B)

57.7045=785.63(A+10B)

.07345=A+10B (used for elimination)

233.608=7.8563+7.8563(419.514A)+7.8563(175992B)

225.7417=3295.83(A+419.514B)

.0685= A +419.514B (used for elimination)

after subtracting the two equations to find B and cancel A I find that B= -1.209x10^(-5)

then plugging back into one of the shorter equations above find A to be .0736, but both of these are supposedly wrong...