10.3 Charges at Work (Pages 418-427)

Learning Goals I can use electrostatics to explain why lightning strikes happen. I can explain how lightning rods work. I can describe practical uses of electric charges, including electrostatic precipitators, electrostatic spray painting, Van de Graaff generators and radiation dosimeters.

A lightning rod is a metal sphere or point that is attached to the highest part of a building and connected to the ground. A lightning rod reduces the likelihood of a lightning strike. If there is a lightning strike, the lightning is more likely to strike the lightning rod than the building it protects, and then to be conducted to the ground.

An electrostatic precipitator removes unwanted dust particles and liquid droplets from a flow of gas.

An electrostatic separator uses induced charges to separate particles that have different masses. A Van de Graaff generator is capable of generating very large charges.

In the dark, selenium is only a fair conductor In the dark, selenium is only a fair conductor. When exposed to light, it becomes a very good conductor. Selenium-coated drums are used in photocopiers, laser printers, and scanners. A radiation dosimeter is a small device that detects and measures exposure to radiation.

Lightning

Lightning

Lightning

Lightning Rods Lightning rod: a metal sphere or point, attached to the highest part of a building and connected to the ground Video: How lightning rods work

Electrostatic Precipitators Electrostatic precipitator: a type of cleaner that removes unwanted particles and liquid droplets from a flow of gas

Electrostatic Spray Painting Paint and object to be painted are given opposite charges  attraction between paint and object Minimizes wasted paint and ensures even coat of paint Especially useful for curved objects

Van de Graaff Generators Van de Graaff generator a device that accumulates very large charges Rubber belt carries electrons away from the sphere, producing a build- up of positive charge

Photocopy Machines Video: How Photocopy Machines Work Discovery Channel Video: Laser Printers

Radiation Dosimeters Radiation dosimeter: a small device that detects and measures exposure to radiation When radiation is present, it knocks electrons from gas atoms in the dosimeter The charged particles are detected by a piece of metal in the dosimeter that behaves like an electroscope

Video1: How Electrostatic Precipitators Work Video2: How Electrostatic Precipitators Work Video3: Electrostatic Spray Painting Video4: MythBusters Build a Van de Graaff Video5: Quartz Fiber Radiation Dosimeter

Practice Page 428 # 1-8