unit 3 static electricity

Unit 3

Static Electricity

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.


Static charges can cause a painful shock!


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.


Grains of sand receive a charge to help them stand

apart when making sandpaper.


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.


Electronic air cleaner or precipitator


Producing a static charge.


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.


Electroscope.


Charging the electroscope with a negative static

charge.


The action of the leaves reveals the polarity of the

pen’s charge.


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.


The typical thundercloud contains areas both

positively and negatively charged.


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.


Lightning travels from negative to positive areas.


A lightning rod provides an easy path to ground.


Useful static charges are often used in spray

painting.


The drum of a copy machine is coated with

selenium.


The drum receives a positive charge.


The image is transferred to the selenium drum.


Negatively charged powder is applied to the

positively charged drum.


The negatively charged powder is attracted to the

positively charged paper.


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.


Review:

5. Static charges accumulate on insulator

materials.

6. Lightning is an example of a natural static

charge.

unit 3 static electricity

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