Conductors

• Conductors are the opposite of insulators because they have little resistance to energy -- they allow the free flow of energy, such as electrical current. Many conductors are metallic but not all metals are equally conductive. There are three basic types of conductors: electrical, thermal and sound.
  
  

Electrical Conductors

• Copper wire is an electrical conductor familiar to most people.Jupiterimages/Photos.com/Getty Images
  
  Electrical conductors permit the free flow of electric current. The amount of current a conductor can carry is determined by its electrical resistance. Good electrical conductors have low resistivity. Determining factors of resistivity are the material and size of the conductor. Larger conductors can carry more current. Silver is the most conductive metal, but is only used in specialized applications due to cost. Copper is the most commonly used metal for light gauge wire applications although aluminum, which is actually a better conductor, has been used to to lower cost. Gold, which can be prohibitively expensive, is used in applications requiring high-reliability surface-to-surface contacts such as microelectronics, because it does not corrode. Not all electrical conductors are metallic. Graphite conducts electricity effectively, as do some salt solutions such as sodium salts which are used to create an electrical arc in sodium vapor lamps.
  
  

Thermal Conductors

• Thermal conductivity is the ability of a material to transfer or move heat. The thermal conductivity of a material determines how quickly or slowly heat moves through it. Cookware is often made of metals such as copper or aluminum because their high thermal conductivity allows them to heat very quickly. Thermal conductivity and electric conductivity often go hand-in-hand, making many metals effective heat and electrical conductors.
  
  

Sound Conductors

• Movie characters often listen for the sounds of distant trains through the steel rails.Jupiterimages/Photos.com/Getty Images
  
  Sound travels in waves. Sound conductors are substances that allow sound waves to move freely through them. The best sound conductors are solids with a dense, elastic molecular structure. Sound travels faster through dense materials like steel because the molecules are closer together and elastic. Air, even though it is the medium through which we hear, is a gas that is a poor sound conductor relative to most solids and liquids. Sound travels faster through water than air. It travels even faster through steel. That is why the sound of a hammer hitting steel is louder if your ear is pressed to the steel surface than if you hear it through the air. Old Hollywood westerns often showed people with their ear pressed against steel railroad tracks, listening for the sounds of a distant train. Science supports this practice. This principle is also illustrated in the phrase "keep your ear to the ground," meaning listen for anything new.