More Van de Graaff Demos

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• More Van de Graaff Demos!!
• Pie plates on top
• Hold Positively-charged pith ball in electric
  field. Observe direction of field
• Rice Krispies in Metal and Plastic Bowls
• Jumping Lights... Application
  Spark Plugs!

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Lightning
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Lightning is produced because of a charge
separation in a cloud The top of the cloud is
__________ charged and the bottom is __________
charged. There are a couple of theories that
attempt to explain why. (See article or ACT
practice question for the details.)
positively
negatively
The negative base of cloud INDUCES ____ on the
ground to move ____ ____ the surface, leaving a
________ charge. We see lightning when e-s seek
out positive charge in the air or ground.
e-s
away
from
positive
4
If you are outside when thunderstorms are in the
area, and you begin to feel your hair stand up
(as did this woman), WATCH out. This is a sign
that the earth (and you!) are getting charged
positively. Lightning could strike at any moment!
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Lightning Rods
Lightning rods are typically thin metal rods that
protect against lightning damage by providing a
safe pathway to the ground for the lightning.
Intense ___ charge builds up at the tip of the
rod, which can then help initiate whats called
an upward-traveling _________. The downward
traveling _______ ________ is attracted to the
streamer. WHEN they contact each other, _____
travel ______ through the channel formed to the
________ ____ and then into the ground.













streamer
stepped leader
e-s
down
lightning rod
Streamer that did NOT connect
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Some Basic Lightning Facts 1. A typical bolt
is about ______ thick.
We know this by analyzing
fulgurites, sand that has been
fused into a glass-like channel
from the intense heat of lightning.
2. Temperature is approximately ___ times
hotter than the surface of the sun! 3. About
_____ bolts strike earth each minute. 4.
Lightning is most likely crooked because
pockets of ___ and ___ charge attract and
deflect lightning bolt.
1 inch
5
THUNDER!
6000
-

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Lightning Questions

• 1. What should you do if you are outside in an
  open area (like a golf course!) during a
  thunderstorm?
• DONT _____________! (like a lightning rod
  tallest thing around)

STAND UP

• DONT ____________! (Ground Current charge
  spreads out once lightning hits the earth. Cows
  are often killed because of this!)

LIE DOWN

• DO _______ or ________!

Squat
Crouch
Ground Current
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2. Is it dangerous to be in a car that is hit by
lightning? ____! But, its NOT because of the
_______ ______. Its because ______ stays on the
________ of the metal frame. (Recall that the
electric field inside a conductor is _____!) 3.
There are many accounts of people living through
a lightning hit, both indirect and direct! How
could a person survive a direct lightning
strike? It helps if the victim is ____! Since
_____ is a better conductor than human flesh, e-s
travel easier through the ______________ on
outside of body.
NO
rubber tires
charge
outside
zero
wet
water
water sheath
Smooth barked trees survive easier than oaks for
the same reason!!
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There are two main ways that people die from a
lightning strike internal burns and heart
stoppage. So, being wet increases the likelihood
that the charge does NOT enter your body and
cause internal burns. IF the heart stops, only
an electric shock (defibrillator) can restore
it. 4. A rain gush is sometimes observed at
the location of a lightning strike. What might
cause this? Before the strike some water droplets
are _________ in the _________________ of the
cloud. When lightning strikes, the _______
strength is reduced, allowing the droplets to
fall.
suspended
electric field
field
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Lightning researchers, like those in the next
video, trigger lightning by firing wire-trailing
rockets into a storm cloud, giving the lightning
a pathway to ground!