Physics Post-Lab 212P-5

Physics Post-lab 212P-5

Resistance and Ohm's Law

Name:______Section:_____ Date:______

Q1. The (United States) National Electric Code, which sets maximum safe currents for rubber- insulated copper wires of various diameters, is given (in part) below. Plot the safe current density as a function of diameter.

Gaugea 4 6 8 10 12 14 16 18 Diameter, milsb 204 162 129 102 81 64 51 40 Safe current, A 70 50 35 25 20 15 6 3

Q2. Which wire gauge has the maximum safe current density?

a A way of identifying the wire diameter. b 1 mil = 10-3 in. Q3. The resistance of a resistor is measured at several temperatures, as shown below. Plot the data and a linear fit to answer the following questions.

T, C 50 100 150 200 250 300 R,  139 171 203 234 266 298

Q4. Find the value of resistance at 0 C, 20 C and 265 C.

Q5. Find the temperature coefficient of resistance (instead of resistivity) with a reference temperature of 20 C.