unit 3 static electricity
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Unit 3 Static Electricity
Objectives:
• Discuss the nature of static electricity.
• Use an electroscope to determine
unknown charges.
• Discuss lightning protection.
• List nuisance charges of static electricity.
• List useful charges of static electricity.
Unit 3 Static Electricity
Charges
• Static charges can be a nuisance, or dangerous, or beneficial.
• Electric shocks from walking on carpet can be annoying.
• Electrostatic discharge can ruin sensitive electronic components.
• Copy machines and sandpaper rely on the application of static electricity.
Unit 3 Static Electricity
Grains of sand receive a charge to help them stand
apart when making sandpaper.
Unit 3 Static Electricity
Charges
• Electronic air filters called precipitators use
static charges to attract small particles in
the air and trap them in the filter.
• The word static means not moving.
• Electrostatic charges build up on insulators.
• A static charge can be positive or negative.
Unit 3 Static Electricity
Electroscope
• The electroscope was an early device that
indicated the polarity of a charged object.
• The electroscope uses a metal ball to transfer a
known polarity charge to thin metal leaves.
• When an object with an unknown charge is
brought near the metal ball, the action of the
leaves reveals the nature of the object’s charge.
Unit 3 Static Electricity
Lightning
• The best example of static electricity in nature is lightning.
• The movement of water droplets in a thundercloud generates a static charge.
• Lightning occurs when the positive and negative areas have the potential difference to overcome the air’s resistance.
Unit 3 Static Electricity
The typical thundercloud contains areas both
positively and negatively charged.
Unit 3 Static Electricity
Lightning Protection
• Lightning rods are used to help protect
objects from lightning.
• Lightning rods provide a safe path to
channel the electric discharge.
• A lightning arrestor is also used for
protection.
Unit 3 Static Electricity
The negatively charged powder is attracted to the
positively charged paper.
Unit 3 Static Electricity
Review:
1. The word static means not moving.
2. An object is positively charged by removing
electrons.
3. An object is negatively charged by adding
electrons.
4. An electroscope is a device used to
determine the polarity of an object.
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