Electrical extension cords are great way to extend circuits to areas that you are working, away from available outlets. Many times, the user doesn't heed the extension cord size compared to the length of the run. Long runs of wire encounter a variable that you may not have considered, resistance. Even though copper wire is a very good conductor, it does have some resistance that causes heat. Heat does damage, not only to the extention cord itself, but also the power tools connected to them.
The longer the run of wire, the more resistance, and thus, more heat. So how does this effect you? Well, power tools draw a certain amount of amperage to run both correctly and efficiently. This electrical load may be too great for the size of extension cord it is attached to. Because of wire size, resistance of the wire, and the voltage drop due to the distance, these variables can damage both extension cords and the power tools that are connected to them.
Voltage drop in the cord often doesn't allow the power tools to run at full speed. This causes them to heat up and often inflicts damage to them. Wiring inside the tools can melt as well as inflicting damage to the contacts. As the power tools heat up, so does the extension cords that they are connected to. That in turn leads to circuit breakers tripping, often due to a heating up of the breaker and/or overloading of the circuit breaker.
To be safe, try not to exceed the extension cord chart below. Be safe, not sorry.
Extension Cord Usage Chart
| Extension Cord Length (Feet) | Maximum Amperage | Wire Gauge |
| 25 | 10 | 18 |
| 25 | 13 | 16 |
| 25 | 15 | 14 |
| 50 | 5 | 18 |
| 50 | 10 | 16 |
| 50 | 15 | 14 |
| 75 | 5 | 18 |
| 75 | 10 | 16 |
| 75 | 15 | 14 |
| 100 | 5 | 16 |
| 100 | 15 | 12 |
