Physics
Physics
Problem
A contractor operates a circular saw from a standard outlet using a extension cord. The two conductors in the cord together have a total resistance of . Treat the saw as a purely resistive load whose internal resistance does not change. (a) Determine the current drawn by the saw when it receives its rated power at with no extension cord attached. (b) With the extension cord in place, calculate the power dissipated as thermal energy in the cord itself while the saw is running. (c) Find the potential difference actually delivered to the saw during operation with the cord attached. (d) Discuss how the reduced voltage in part (c) affects both the mechanical performance of the saw and the overall electrical safety of the setup. Reference your quantitative results in your explanation.Intuitive explanation
The key insight is that the extension cord itself acts as a resistor in series with the saw, so the voltage actually reaching the saw is less than 120 V due to a voltage drop across the cord. You'll need to find the current the saw draws, use that to calculate the voltage lost in the cord's resistance, and then determine what voltage and power the saw actually receives—which will be different from the nameplate values because of this "voltage sag."
Intuitive explanation
The key insight is that the extension cord itself acts as a resistor in series with the saw, so the voltage actually reaching the saw is less than 120 V due to a voltage drop across the cord. You'll need to find the current the saw draws, use that to calculate the voltage lost in the cord's resistance, and then determine what voltage and power the saw actually receives—which will be different from the nameplate values because of this "voltage sag."