Presentation on theme: "How Static Electricity Affects Our Daily Lives. An example of a very large electrical discharge (when electric charges are transferred very quickly)"— Presentation transcript:
An example of a very large electrical discharge (when electric charges are transferred very quickly) caused by induction A charged area – usually negative – builds at the base of the cloud This creates a temporary positive area on the ground (induction) When enough charge has built up, a path of charged particles forms and the cloud discharges its excess electrons on the path to the ground
Pearson Investigating Science 9 10.2 Lightning Lightning is caused by negatively- charged clouds discharging ions to the ground. Clouds have a negative charge on the bottom and a positive charge at the top. 1c. A positive charge is induced in the earth. 1a. Cloud is negatively- charged. 3. Cloud sends a negative “ stepped leader ” towards the ground. 4. Ground send up a stream of positively- charged air ions. Electrons move deeper underground When the two meet the cloud discharges starting with the negatives near the ground then working its way step by step back to the cloud. 1b. Electrons move deeper underground to get away from negative cloud. a b c d
About 65% of lightning bolts go from one cloud to another without ever touching the ground! The total amount of energy released as light, heat, and sound during one major thunderstorm is much greater than that released from one nuclear bomb! Over 100 bolts of lightning strike the earth every second! The temperature of the air near a lightning bolt can reach as high as 33 000 degrees Celsius! Hotter than the surface of the SUN!!
The light from lightning travels so fast that it takes almost no time to reach us. The sound from thunder takes about 3 seconds to travel 1 kilometre. This means you can tell how far away lightning is by measuring the time between the flash and the sound. TRY IT!! Imagine your heard thunder 9 seconds after you saw the lightning. How far away were you from the bolt? You were 3 kilometres away!!
This is a metal pole with a wire attached to it that runs down to the ground. By being a sharp point, it leaks out the positive charge that a cloud induces in a building. If lightning hits the rod, the flow of electrically charged particles is directed harmlessly away from the building and down to the ground so the building is not damaged. Since electrons don’t go through the building, they cannot heat it enough to start a fire.
Why do we ground objects? To prevent fires, explosions, and shocks Vehicles build up charge through friction between the outside of it and the air Cars use ground straps to prevent a build up Airplanes have needle-like projections on wings and body that disperse static charges into the air The consequences of no grounding http://www.pei.org/PublicationsResources/Safety Resources/StopStaticCampaign.aspx http://www.pei.org/PublicationsResources/Safety Resources/StopStaticCampaign.aspx
Why would clothes made of different materials stick together when they come out of the dryer? Static charges build up through charging by friction. Charging by friction creates opposite charges. Opposite charges attract and then stick together.
What do we do about it? Antistatic dryer sheets Adds a thin layer of waxy material to the surface Less friction Fabric softener Coats the surface of the cloth fibres with a thin layer of chemicals which lubricate and are electrically conductive Antistatic spray Works in a similar way as the fabric softener
Sparks can also damage electrical equipment. Some ways that we can reduce the risk of sparks are through: Using an antistatic mats Using a humidifier Spraying the carpet with antistatic spray Wearing an antistatic wrist strap Getting rid of the carpet entirely
What is the function of a lightning rod? How is charge build-up reduced on airplanes? Why is a ground strap a necessary safety feature when transferring fuel? What are three different methods for reducing charge build-up in clothes dryers? What are four different methods for reducing charge build-up in a computer room with a carpet?
Spray Painting The paint coming out gains a negative charge. When the surface of the object is charged positive, so the paint becomes attracted to the object. Photocopying Means to copy using light Electrostatic Precipitator Used in factories, mining, plastics and paper recycling Cleans the air by charging the matter in the gas before it is released and running it by charged plates. The plates attract the particles and remove them from the gas.
Ground or charge the object to be painted by attaching a charged wire. Negative Charge Air Paint
Photocopying 1. Positive charge created on the drum, which is a photoconductor. 2. Image is projected onto drum. Where light hits drum, it becomes neutral; dark areas remain charged. 3. Negatively charged ink is sprayed onto drum and sticks to it. 4. Paper is pressed onto drum, where heat and pressure fuse ink to paper. 5. Paper is still charged and warm when it comes out.
Waste gases without smoke particles 1. Smoke particles pick up a negative charge 2. Negatively-charged smoke particles are attracted to positively- charged collecting plates 3. Collecting plates are removed and knocked to remove smoke particles. Positively-charged collecting plates Negatively-charged metal grid Waste gases containing smoke particles
Quick Lab on page 424 of the textbook I will be randomly choosing the pairs this time! You will need: paper, scissors, petri dish and lid, two small pieces of tape, some cocoa, wool cloth You will be given about 15 minutes to complete this lab You will then be able to work with your partner at answering the chapter questions