1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution 1. A copper rod, 100 mm long and 2.5mm diameter, has a resistance of 340micro ohms at 15degrees Celsius. If the rod is drawn out into a wire of uniform diameter 0.5mm, calculate its resistance at 60 degrees Celsius. Assume the temperature coefficient of resistance to be 0.0043/degree Celsius at 0 degrees Celsius. 2. R1/R2=1+alpha0xt1/1+alpha0xt2 3. (340 uohm)(L2/L1) / (R2/R1)^2 = (340 uohm)(2500/100)(2.5/0.5)^2 = 0.2125 ohms. Then use the temperature equation: R = (0.2125 ohm)(1 + 0.0043*45) = 0.25 ohms ^^ This is an answer that I found online but I don't know where the person got the 2500 value for L2 from? The answer given in the textbook is R=0.251ohms Thanks, Devon.