Transcript Conduction and Induction

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
The charged regions within the atmosphere
temporarily equalize themselves through a lightning
flash
1. Cloud to ground
2. Cloud to cloud or Intracloud
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.
Sheet Lightning
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.
Heat Lightning
Lightning from a thunderstorm that is
too far away to be heard.
Forked Lightning• Has branching in its paths
Ball Lightning
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.
Fulgarites
http://www.madebymeg.net/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.
Lightning’s affect on Humans and Animals
• Most common cause of
death is cardiac arrest
– In humans 70% of victims
survive because CPR was given
in time
– Animals have a nearly 100%
mortality rate because CPR is
unable to be given to them
• Most common visual injury is
burns
Induction
• The charging of an object without direct
contact
Induction
Grounding
It acts as overvoltage
protection in the case of
lightning or a power
surge.
The extra electrons go
into the earth.