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Lightning - PowerPoint PPT Presentation

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  1. Lightning

  2. Bellringer • What causes lightning?

  3. Objective • Explain what causes lightning.

  4. Lightning Video • • How do scientists get better information on lightning strikes? • What do scientists believe triggers lightning strikes? • What evidence is there to support this theory?

  5. Where is Lightning? • Lightning is most commonly developed within a thunderstorm • Lightning has also been seen with in volcanic eruptions, heavy snowstorms, and in large hurricanes.

  6. Formation of Thunderstorms • A thunderstorm forms in air that has three components • Moisture • Instability • Something such as a cold front to cause the air to rise • The rising motions within the storm can build a cloud from 6 to 10 miles above sea level.

  7. Formation of Lightning • At this elevation temperatures are much colder; so ice begins to form in the higher parts of the cloud • As the falling ice and sleet collides with the rising moist air, it picks up extra electrons from the ice and sleet. • The ice and sleet then deposits these electrons at the bottom of the thunderstorm cloud.

  8. Formation of Lightning • The separation of charge is crucial for lightning to form. • The separated charges cause the bolts of lightning we see. • The more charge that is separated the bigger the strike.

  9. Bellringer • What do scientists currently believe is the mechanism for triggering lightning strikes?

  10. Objectives • Review the tornado quiz • Investigate how separating electric charges can produce electrical sparks similar to lightning bolts so we can explain the phenomena.

  11. Tornado Quiz • Class average was 85

  12. Separation of charge?? • What does separation of charge mean? • Atoms are normally neutral (meaning they have no charge) • However you can remove electrons from certain atoms and put them somewhere else.

  13. Separating Charge • Some atoms (typically metals) don’t care about all of their electrons so they can be removed or shared with another atom. • How can you remove extra electrons from an atom?

  14. Separating Electrons Demos • Balloon Demo • Opposites Attract Demos • Likes Repel Demo • Sparks Demos

  15. Lightning in a Cloud

  16. Van De Graaff Generator

  17. Bellringer • How is static electricity built up in a thunderstorm cloud? • The falling ice collides with the moist rising air to transfer electrons to the bottom of the cloud. Thus leaving the top of the cloud with a positive net charge.

  18. Objectives • Know the differences and similarities of CG, CC, and IC lightning strikes. • Understand the frequency of lightning strikes around the world. • Know what causes thunder and be able to calculate your distance from a lightning strike based on the time delay of thunder.

  19. Lightning • Lightning is approximately 50,000 degrees Fahrenheit • The average lightning bolt is hundreds of millions of volts and typically about 50,000 amps

  20. Types of Lightning There are two types of lightning • Cloud to Ground – 10% • Cloud to Cloud or Intra-Cloud – 90% • CC and IC lightning are far more common than CG lightning, but CG lightning has a greater effect on humans so more research has been done on that.

  21. Cloud to Ground Lightning • As a thundercloud moves over the surface of the Earth it induces a positive charge on the surface. What happens to the taller objects? Can you become the tallest object around?

  22. CG Lightning • These two oppositely charged objects create a strong electric field. • An electric field stores energy that can be released at a later time. Similar to a battery. • Once triggered this energy is released in the form of a lightning bolt.

  23. CG Lightning • Normally air is an insulator and will not let electrons flow through it. • When enough energy is applied a path to Earth becomes “ionized”. • This ionized path is light a highway for the electrons to travel on.

  24. CG Lightning • Once the bottom of the cloud and the Earth’s surface are neutral again, the ionized highway closes down. • While that path of air is ionized, the air acts as a conductor instead of an insulator.

  25. Flash of Lightning? • Lightning seems to happen is one bright bolt but is that really what happens? • Let’s take a look: •

  26. CG Lightning • Why does the main lightning bolt seem to pulse in slow motion? • It takes the electrons a few moves from cloud to ground and back to cloud until they are evenly distributed.

  27. Cloud to Cloud and Intra Cloud • This is more common than CG lightning, but it doesn’t cause nearly as much destruction because it doesn’t hit anything or anyone. • It also won’t appear as bright or as loud because it is buried in the cloud, and typically further away than CG lightning.

  28. Cloud to Cloud Lightning • CC lightning occurs between two separate clouds. • The lightning process is the same as CG, but it between a negative part of one cloud and a positive part of a different cloud.

  29. Intra-Cloud Lightning • IC lightning is when a lightning bolt strikes within one thunderstorm cloud. • Lightning bolt between the positive top and negative bottom of the thundercloud. • This is even more common than CC lightning because the particles in the thundercloud make it easier to conduct electricity.

  30. CC and IC Lightning

  31. Airplane Lightning

  32. Space Lightning

  33. CG, CC, and IC Lightning

  34. Checkpoint • Explain the differences between CG, CC, and IC lightning strikes. • How are CG, CC, and IC lightning strikes similar?

  35. Frequency of Lightning Strikes • On Earth, the frequency of lightning is approximately 40 to 50 times a second! • That’s nearly 1.4 billion flashes per year! • Lightning strikes everywhere on Earth, but is more common on land over the tropics (70%)

  36. Lightning Capital of America • Florida sees more lightning than any other area in the USA • Lightning Alley is from Tampa to Orlando • As many as 50 strikes per square mile a year • The Empire Stat Building is struck on average 23 times each year • Was once struck 8 times in 24 minutes

  37. Lightning In America • This website tracks every lightning strike in America… •

  38. Thunder • Thunder is the sound caused by lightning • It is so loud because it is a sonic boom. • Meaning that it has so much energy that is causes the air particles to move faster than the speed of sound • Thunder IS NOT the collision of clouds. There must be lightning for there to be thunder.

  39. Thunder • The distance of the lightning can be calculated by the listener based on the time interval from when the lightning is seen to when the sound is heard. • The lightning is approximately one mile away for every 5 seconds between sound and flash.

  40. Storm Watch • How far away is the lightning bolt if you see the flash and the 15 seconds later you hear the thunder?

  41. Summary • Why does CG lightning typically hit the tallest object in the area? • What state has the most lightning strikes? • What causes thunder?

  42. Dangers

  43. Safety

  44. Lightning Rods