Presentation for Junior Level Students


Learning outcomes:

  1. Atom:

-     An atom is the basic building block for everything. It is made of protons (positive charge), electrons (negative charge), and neutrons (no charge)

-     I will emphasize on the protons (example: basketballs) which are big and stable as well as electrons (tennis balls) which are smaller and mobile

-     The Bohr model is much like planets orbiting the sun (with the protons being the sun and electrons orbiting around it)


  1. Like charges repel / Opposite charges attract:

-          Illustrate with boy / girl analogy (when two boys or girls come together, they repel one another; when a boy and a girl come together, they attract)

-          Let us start off with an atom that has 3 basketballs and 3 tennis balls. If we steal some tennis balls, what happens? The atom becomes positively charged which will now attract to tennis balls from other neutral atoms

-          Glass rod and Silk cloth demo (explained in the Apparatus section under Demo #1)

-          Comb and Hair demo (explained in the Apparatus section under Demo #2)


  1. Van de Graff Generator:

-          The fundamental principle behind this apparatus is separating opposite charges at both ends of the rubber belt

-          Materials (explained in the “How to Build a Van De Graff Generator” section)

-          Due to difference in materials, the belt strips electrons from the dome and transfers it to the bottom. So what happens to the dome? There are now excessive basketballs spread out all over its surface

-          When we touch the generator, tennis balls in our bodies want to attract to the basketballs spread out over the dome. This leaves us positively charged. We are now a part of the generator and the belt is basically stripping electrons from us instead

-          Our hair is originally neutral, but the tennis balls move away upon contact. Since there are mostly basketballs left on each strand of hair, the like charges will repel each other (making our hair stand up)

-          Hair raising demo (explained in the Apparatus section under Demo #3)

-          Electric spark demo (explained in the Apparatus section under Demo #4)


  1. Conclusion:

-          The same principle of static electricity applies when we feel a shock upon touching a metal doorknob on a dry winter day



Watch PowerPoint presentation




How to Build a VDG


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