Final answer:
Nicks or poor connections in wires can increase resistance, which decreases current and power delivery to devices and can generate heat, potentially impacting appliance performance.
Step-by-step explanation:
Nicks or poor connections effectively create a smaller wire, which can cause a reduction in the current and power delivered to an appliance or device. This happens because such imperfections increase the resistance in the wire, leading to a larger voltage drop across it. When the resistance is large, as would be the case with a worn or very long extension cord, the loss in power can be quite significant. A large current draw increases the IR (current × resistance) drop, which can become apparent through the heat generated in the cord. Moreover, if the voltage drop is large due to the resistance of the extension cord, the voltage supplied to the appliance is reduced, which decreases the power output and can affect the appliance's performance.