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METALS, INSULATORS AND SEMICONDUCTORS

This video explains the difference between a metal, insulator and a semiconductor with emphasis on what a semiconductor is. This video also emphasis a semiconductor's role in computing, and electrical transitions due to heat. Be sure your students understand how light can be used instead of heat to cause the electrons to move between the bands. See our page on different energy types if you need help explaining this concept.

Possible discussion topics:
  • In this video, heat is used to promote electrons from the valance (lower energy) to the conduction (higher energy) band, but light can also be used. It also mentions that light can also be used. Why can light also be used?
  • Semiconductors have a bandgap (a gap between the valance and conduction bad). Would the amount of energy applied to a semiconductor (heat, red light, blue light) effect a semiconductor's performance?
  • Would re prefer a semiconductor with a large bandgap or a small bandgap to make solar panels with? Why?
  • How would you predict the bandgap of a material would relate to the maximum voltage from a solar cell made from that material?
THE PHOTOELECTRIC EFFECT

This NOVA video explains what we mean when we say "energy".

Possible discussion topics:
  • What types of energy can your body have? Give an example of each
  • Which types of energy conversion are more or less efficient? Remember, energy is neither created or destroyed, but why about entropy?