Final answer:
Extension cords can be used indefinitely if not damaged and used within their rating, but cheaper or longer cords can result in a voltage drop and power loss. This affects the power output and efficiency of connected appliances due to increased resistance and heat dissipation.
Step-by-step explanation:
Extension cords are used to provide power to an appliance or device that is located at a distance from a power outlet. When using an extension cord, it's important to ensure it is rated for the power requirements of the appliance and for the environment in which it will be used. The length of time an extension cord can be used is indefinite so long as it is not physically damaged and it remains within its operational ratings. However, the power output of an appliance can be affected by the use of an inadequately rated extension cord.
An example of the potential issue is when a long, inexpensive extension cord is connected to a high-power appliance like a refrigerator. The refrigerator might not run as it should because the cord might have higher electrical resistance due to its length and the thinner wire used. This results in a voltage drop along the extension cord, which reduces the voltage and thus the power supplied to the refrigerator. For example, an extension cord with a resistance of 0.0600 ohms through which 5.00 A is flowing would have a voltage drop of 0.300 V (calculated by Ohm's law, V = I * R). In contrast, a cheaper cord with a higher resistance of 0.300 ohms would result in a voltage drop of 1.50 V.
A more technical explanation involves calculating the power dissipated in the extension cords. Using the formula P = I2R, where P is power, I is current, and R is resistance, we can assess the power lost in the cord as heat. A good quality extension cord would dissipate less power than a cheaper cord with higher resistance, leading to less energy waste and a smaller reduction in voltage reaching the appliance.