A3

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A3  Lightning and Thunder
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           DEFINE LIGHTNING 

• Lightning is the large electrical discharge that
  occurs between two oppositely charged areas.

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DEFINE THUNDER

• Thunder is the sound that results from the rapid
  expansion of air along a lightning strike.

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How Lightning is created
Updrafts and downdrafts (convection currents)
move ice crystals and water droplets through a
cloud, their movement creates posotive and
negative charges.
STEP 1
A moving thunderstorm gathers another pool of
positively charged particles along the ground
that travel with the storm. this is why
sometimes, if you stand outside in a lightning
storm, your hair stands on end.
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A channel of negative charge, called a "stepped
leader" will descend from the bottom of the storm
toward the ground
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Once the step leader's channel is complete, the
circut will close and the positively charged
electrons from the ground run to the negative
charged ones and back. We call the electricity in
this situation lightning. The example shown is
called cloud to ground lightning. If the step
leader forms from the negative and positive
charges in the cloud, lightning occurs within the
cloud, which is called cloud to cloud lightning.
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THUNDER

• How it is created
•  
• Lightning is extremely hot (up to 54,000ºF). 
•  
• The heat causes the air to quickly expand and
  contract faster than the speed of sound (768
  mph). 
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• This creates the sound waves we hear as thunder.
•  
• Sound is created when the air vibrates - the air
  vibrates your eardrum and you hear sound.  The
  rapidly expanding air causes the air to vibrate
  and produce sound.

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Thunder

• Does lightning travel faster than thunder?
•  
• Yes, lightning is light and light travels to the
  eye at a speed of 299,792,458 metres per second
  while thunder is sound and travels to the ear at
  a speed of 344 metres per second.

light
sound
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What Cloud Type Creates Lightining and Thunder?

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• The cumulonimbus cloud is the cloud that creates
  lightning and thunder. Low air pressure creates
  this cloud!

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The Risks...

• - You can get shocked
•  
• - Electrocution
• - Forest fires
• - Injuries can occur if someone is struck by
  lightning or if an object is struck by lightning
  and it falls on someone.

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Fun Facts about Lightning and Thunder!

• - Lightning often strikes outside of heavy rain.
• - A flash of lightning is no more than one inch
  wide.
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• - Lightning has "favorite" sides that it may hit
  many times in one storm.
• - In one place there may be 4 different strokes
  which makes lightning appear to flicker.