Question

Felix has placed some Copper wire (where the official looked up inferred absolute temperature is 234.5 Celsius) 28 gauge wire in a freezer at 15.3 degrees Fahrenheit. He measures the resistance of the COLD wire to be 15.3 ohms. What is the length of the wire in units of feet?

Answer 1

2.14 ft

Step-by-step explanation:

We will use the following equation:

`L = (R_(T) * A)/(p_(20C)*(1+\alpha _(20C)*dt ) )`

Data obtained:

`R_(15.3 F , -9.27 C) = 15.3 ohms\\A_(28-gauge) = 8.2*10^(-8) m^2\\p_(20 C) = 1.723*10^(-6)\\\alpha _(20C) = 0.00393\\ dt = 20 - (-9.27) = 29.28`

Using the above equation:

`L = (15.3 * 8.2*10^(-8))/(1.723*10^(-6)*(1+0.00393*29.28 ) )\\\\L =0.6530 m = 2.14 ft`