ELECTROSTATICS IN OUR LIVES

How Static Electricity Affects Our Daily Lives

Lightning

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

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

Some Shocking Facts!

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!!

Did You Know?

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!!

Lightning Rods

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.

Lightning Rods

The Dangers of Static Electricity

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/SafetyResources/StopStaticCampaign.aspx

Reducing Static Charges In The Home

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.

Reducing Static Charges In The Home

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

Reducing Static Charges In The Home

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

Checkpoint

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?

How We Take Advantage Of Static Charges

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.

Spray Painting

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.

Electrostatic Generator 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

Make Your Own Photocopier

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