Electrical Conductors

• A material is an electrical conductor if electric current flows relatively easily through it in response to an applied voltage. Metals such as copper, aluminum and gold are good electrical conductors.
  
  

Electrical Insulators

• A material is an electrical insulator if current does not flow through it when a voltage is applied. Wood and rubber are good electrical insulators.
  
  

Atomic Structure of Conductors

• Good conductors have many free electrons that are not tightly bound to atoms. These electrons will migrate toward a positive electric pole, resulting in an electric current.
  
  

Atomic Structure of Insulators

• Insulators do not contain many loosely bound electrons. When a voltage is applied across an insulator, few free electrons are available, so no current flows.
  
  

Temperature and Conductivity

• For most conductors, conductivity is a function of temperature. As the speed of randomly moving electrons increases with temperature, they are more likely to interfere with the directional flow of an electric current.
  
  

Conductivity and Cross-Section

• Conductors with a large physical cross-section conduct better than those with a smaller cross-section. Large-diameter wires have less resistance to current flow and can conduct more current than small-diameter wires.