Charging by Friction and Contact：通过摩擦接触充电.pptVIP

Vocabulary Quiz-Thursday Charging by Friction and Contact Charging by Friction and Contact When electrons are transferred by one material rubbing against the other Van de Graaff Generator Invented by American physicist Robert Van de Graaff, 1929 Why this happens Friction Charges can separate from one another in clouds, due to friction Cloud to ground Cloud to cloud or Intracloud The charged regions within the atmosphere temporarily equalize themselves through a lightning flash Cloud-to-ground lightning occurs when negative charges accumulate in the lower portions of the cloud. Positive charges are attracted to a relatively small area in the ground directly beneath the cloud establishing a large voltage difference between the ground and the cloud base. About 80 percent of all lightning is cloud-to-cloud lightning, or sheet lightning (b/c it lights up the sky with a sheet of light), which occurs when the voltage gradient within a cloud, or between clouds, overcomes the electrical resistance of the air. The result is a large and powerful spark that partially equalizes the charge separation. Sheet Lightning Heat Lightning Lightning from a thunderstorm that is too far away to be heard. Forked Lightning- Has branching in its paths A bizarre type of electrification called ball lightning appears as a round, glowing mass of electrified air, up to the size of a basketball, that seems to roll through the air or along a surface for 15 seconds or so before either dissipating or exploding. Seen escorting bomber planes in World War II just off their wingtips. Pilots referred to it as “foo fighters” as they initially were thought to be enemy planes. Ball Lightning Fulgarites/blog/sea-glass-made-from-lightning/ Hollywood Reality A hollow fragile rock The benefit of lightning Heat and pressure from lightning also breaks down the nitrogen in our air to a useful form. The nitrogen acts as a natural fertilizer. Most common cause of death is cardiac arrest In humans 70% of