2 What Causes Lightning?What we know…Strong winds inside clouds cause collisions between water droplets and ice particlesThese collision strip electrons from some particles and deposit them on othersStrong updrafts in the clouds carry smaller particles up while heavier ones drift downNegative charges collect at the bottom of the cloud where the temp is above -20The higher, colder parts are positively charged
3 Lightning …Part 2…Negative charges on the bottom of the cloud repel electrons on the surface of the earthThe ground now has mostly positive chargeNow it works just like any sparkThe strong attraction between the cloud and ground pull electrons off atoms in the airThis creates a pathway of ions for the spark to travel on.This normally occurs on a high point - why do you suppose that might be?
5 Digging a tunnel through the air The electric field becomes very strong (tens of thousands of volts per inch),The air to begin breaking down.The electric field causes the surrounding air to become separated into positive ions and electrons; the air is ionized.The electrons and positive ions are farther apart than they were in their original structure.Essentially, the electrons have been stripped from the molecular structure of the non-ionized air.
6 What about that noise we hear? Many electrons crash though the air at very a high speed - this causes intense heat as well as lightTemperature of the air in and near lightning can reach 33,000ºC - several times hotter than the surface of the sunThis heat causes the air to expand rapidlyAir molecules colliding with other air molecules produce a shockwave we know of as thunder.
7 What does lightning do?Lightning strikes can kill people, knock out radio communications, electrical power, destroy houses or trees.When a person is struck by lightning the chances are about 50% that it will be fatal.Usually, the lightning enters the head or one of the ears.lightning usually strikes out of the body skin again after a few centimeters,a person usually suffers cardiac arrest, apart from burns, temporary blindness and deafness.In many cases neurons are permanently damaged.When a tree is struck by lightning the liquids inside the trunk and branches turn to gas instantly, leading to high pressure and literally an explosion of anything that is between the gas and the open air.
8 Usually, the lightning current runs just underneath the bark, down to ground, and the tree is scarred by a strip of blown-away bark.Sometimes, the current may run down near the center of the trunk. There may be little left of the tree afterwards.When a house is hit by lightning, the electrical current will find its way down by anything conductive, preferably around the perimeter of the house.This may include antennas, plumbing and gutters.Any person taking a bath, making phonecall, washing hands, or otherwise touching metal plumbing either directly or indirectly, may be shocked or killed.Electrical appliances are likely to be damaged or destroyed, either by large peak currents or by the electromagnetic shock wave.
9 Lightning Rods We can’t prevent lightning from striking. How can we control damage done by lightning?Direct the flow of electrons away from the building to prevent fires.Where do electrons travel most easilyLightning rods are made of metal conductors
10 Using Static Electricity Everyday Electrostatics can help us solve problemsElectrostatic precipitators help to clean the airA strongly charged conductor runs up the muddle of the chimneySolids in the smoke get ionizedThey then cling to the sides of the chimney and are scrubbed offCould you design a home air cleaner based on the same principles?
11 Painting with Charges How do new cars get such a smooth coat of paint? The cars are given a positive chargeThe paint is given a negative charge as it leaves the paint gun.The result is a smooth even coat of paint.
12 More Everyday Electrostatics More uses for static electricitySeparating salt and pepperSeparating minerals and oresDust mops.….. Can you come up with any more?