GED Science Practice Test: Conductors, Semiconductors, and Insulators
Static electricity: Static electricity is an imbalance of electric charges within or on the surface of a material that remains static, or still, for some period of time. Static electricity can move, but not in a consistent manner. Thus, static electricity is not used to power electrical devices, because of this inconsistency. Some common examples of static electricity are when your hair stands up after pulling on a sweater, or when you get zapped by a doorknob in the winter.
Current electricity: Current electricity is electricity that flows through wires or other conductors and transmits energy in a consistent fashion. Current electricity is used to power electrical devices. We will learn more about current electricity later in this lesson.
Many different types of materials can hold an electrical charge, but only some are capable of carrying current electricity.
Conductors: Conductors are materials that permit electrons to flow freely from particle to particle. Conductors are good at allowing electric current to move through them and even into another object, especially if the second object is made of a conducting material. Most solid conductors are made of metal. The inside of an electrical wire is made of copper, and is an example of a conductor. However, some saltwater solutions can also conduct electricity.
Insulators: In contrast to conductors, insulators are materials that do not allow the free flow of electrons from atom to atom and molecule to molecule. While insulators are not useful for transferring charge, their ability to prevent charge from moving to certain places makes them very useful. The reason that electrical wires do not pass their electrical charge onto humans, is because they are coated with plastic or rubber, both examples of insulators.
Semiconductors: The division of materials into the categories of conductors and insulators is a somewhat artificial division. It is more appropriate to think of materials as being placed somewhere along a continuum. Materials that are highly conductive (known as superconductors) would be placed at one end and the least conductive materials (best insulators) would be placed at the other end. Metals would be placed near the most conductive end and glass would be placed on the opposite end of the continuum. In the middle would be what are called semiconductors, substances whose electrical conductivity is between that of a conductor such as copper and that of an insulator such as glass. Semiconductors are the foundation of modern electronics, including transistors, solar cells, and light-emitting diodes (LEDs).
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Which of the following is not a good conductor?