• A material that lets electrons flow through it is called a CONDUCTOR
• The molecules of all types of conductors resist the flow of electrons to some degree
• ELECTRICAL RESISTANCE is a measure of how easy or hard it is for electric current to move through a material
  • • Conductors have low resistance
    • Insulators have high resistance (little or no current can move through them)

Factors affecting resistance of a wire

• Wire length
  • Longer wire equals greater resistance

• Wire thickness
  • Thick wires equal low resistance
  • Large electric currents can move through thick wires easier

• Material wire is made of
  • Copper and aluminum have low resistance and are used to carry current over a long distance
  • Tungsten has high resistance so it gets hot as electric current moves through it so it is  used in light bulbs

• Wire temperature

• Cooler wire equals lower resistance
• If the temp. increases, the atoms of the wire are moving faster and the electrons bump into them more making it harder to travel past them in the wire
• Super-conductors lose all resistance at low temp. e.g. Mercury is a good conductor at room temp. but is a super-conductor at –270 degrees.