- 190

- 0

**1. An 80-cm-long wire is made by welding a 5.50 mm-diameter, 20-cm-long copper wire to a 5.50 mm-diameter, 60-cm-long iron wire. What is the resistance of the composite wire?**

**2. p = resistivity, R = pL/A**

**3. r = 0.001375 m goes into A = pi*r**

My calculation came out to be 9.80*10

^{2}. I used the above equation for R separately for the length of the wire for each metal, then added them together. I figured they would just add linearly like resistors in series.My calculation came out to be 9.80*10

^{-3}ohm + 5.72*10^{-4}ohm = 0.0104 ohm = 10.4 milliohm