Competency #8
Answer and Explanation
A certain piece of copper wire has an electrical resistance of 4 W . Indicate what effect each of the following changes will have on the wire's resistance.
Answer:
First, we will acknowledge that electrical resistance results from the collisions of electrons with atom nuclei in the wire.
The length of the wire is doubled. The longer the path electrons must travel, the greater the number of collisions. Therefore, the electrical resistivity will be higher in the longer wire.
The thickness of the wire is doubled. A thicker wire makes it less crowded for the electrons traveling in the wire. There will be fewer collisions, and thus less a lower electrical resistivity in the thicker wire.
The material is changed from copper to plastic. All metals, including copper, have at least one free electron per atom. Electrons that are not bound tightly to a particular atom allow for the free movement of charge. On the other hand, the electrons in plastic are all more tightly bound. It is much more difficult for electrons to move through a piece of plastic. This means the electrical resistivity for plastic is higher than that for copper.