ES Lesson 1: What is the science of electricity?

• What is science?• What is electricity? • How is electricity made and distributed? • What is a fuse? What is a circuit breaker? • How can household electricity hurt us if we don’t

understand how it works?

© 2012 C. Rightmyer, Licensed under The MIT OSI License, 20 July 2012

Jake has a hypothesis: He thinks eating mushrooms will help him grow more hair.

• What is the scientific method and how could he use it to prove or disprove his theory?

– Observation (and research)

– Hypothesis (or theory)

– Predicting expected test results

– Designing and conducing tests

– Making conclusions from the test results

• How could we design a test to see if Jake’s theory is correct?

Jake lived 1.5 million years ago. How do archeologist know that?

Early Greek philosophers used logic and thought to explain life. The scientific method came later.

• Thales of Miletus (582 BC) suggested that water is the basic substance of life.

• Anaximenes of Miletus (535 BC) counters that air is the fundamental substance.

• Empedocles of Acragas (445) suggests there are four different fundamental elements: earth, air, water, fire

• Leucippus of Miletus (435 BC) proposes that the basic elements are tiny corpuscles that he called “atoms” -- meaning indivisible. He was on the right track but did not have adequate methods for testing his theory.

Http://realscience.breckschool.org/upper/fruen/files/Enrichmentarticles/files/History.html

In 150 AD, Ptolemy constructed a working model of our solar system.

http://en.wikipedia.org/wiki/File:EB1711_Armillary_Sphere.png

• This model was well accepted by scientists and religious leaders of his day.

• His model was useful for developing time keeping and navigation methods.

• But, his model incorrectly assumed our earth as the center of the universe.

Copernicus publishes a new heliocentric theory of planetary revolution (1543 AD)

Http://en.wikipedia.org/wiki/Nicolaus_Copernicus

Http://www.ScientificAmerican.com/ (Jan 2014)

• It took more than 200 years for the scientific community to agree that Copernicus was correct. Why?

• If true…..– What could possibly make our

heavy earth move?– The universe must be vast beyond

belief. – Distant stars must be impossibly

large.

1910 Ford Model R

Note: this automobile has been beautifully restored. By 1910, you wouldn’t see power poles or a parking lot.

What are some electricity powered devices that we take for granted today?

• Ovens, cooktops, toasters

• Microwave ovens

• Electric blankets

• Radiant heaters

• Lights

• Dishwashers

• Refrigerators

• Vacuum cleaners

• Televisions, radios, stereos

• Clocks

• Drills, saws, air compressors

• Electric motors/cars

• Batteries and battery chargers

• 3-D printers

• X-ray machines

• Thermostats

• Computers/pads

• Smart phones

• Irrigation systems

Only 105 years ago, how did people live without electricity? For instance, how did they:

• Cook food and stay warm.• Read books at night.• Obtain drinking and bathing water. (Could you

shower?) • Go to the toilet.• Save perishable food.• Clean the floors and rugs.• Communicate with neighbors and friends. • Get the news.• Make wood and metal products.• Do math problems.• Know the time of day.• Make beer, wine, and Manhattans.

(Who knows what mead is and what it’s made of?)

What is electricity?

• Electricity is a handy form of energy that we can use for doing work.

– Electricity generators create an electromagnetic force.

– This force causes electrons to flow through conductive materials.

– Kinetic energy from the flowing electrons is consumed by electric devices (lightbulbs, motors, and such) in order to do work for us.

There are two types of electricity that we will learn about in this course.

(1) Alternating Current (AC) electricity. The kind that we get from the power grid.

(2) Direct Current (DC) electricity. The kind that we get from a battery or an AC/DC adapter.

Where is AC electricity made and how is it delivered to us?

Electricity and Magnetism, Gareth Stevens Publishing, Steve Parker, 2007

ES demo 1-1. A steam driven reciprocating AC power generating plant

A scale model of James Watt’s steam powered electric generator

BE demo 1-1

A steam turbine rotor

Picture of a modern AC power generator.

Picture of a modern AC power generator.

http://www.mpoweruk.com/steam_turbines.htm

Ever wonder how you replace a power pole?

It’s a tricky job installing a new transformer!

How does AC electricity get from the power lines into our homes?

Main breaker box

Wires from the power lines

ES demo 1-2. Main breaker box with its outside cover is open

Individual circuitbreaker switches

Whole house shut offswitch

BE demo 1-2

ES demo 1-3. View of circuit breakers behind the inside cover.

BE demo 1-3

ES demo 1-4. A surprising demonstration of electrical power delivery to your wall outlet.

BE demo 1-4

What happens if we connect the lightbulb’s white wire to the green wire.

“Accidentally” connect the black wire to the white wire and see what happens.

ES demo 1-5. How a fuse works.

Gateways School, Lewis Camp, 2009 (Possibly from Teching Electricity, Yes You Can, Scholastic Professional Books, )

Alligator clip wires.

Desk protectorA few strands of steel wool

Two D-cell batteries in series

What if you accidentally touched both the black and white wires to your body?

Cook a vienna sausage with a pair of open electrical wires. The sausage smokes and turnsblack where the wires are attached. Many kidswant to eat it afterwards, but since this is a school situation rather than a campsite, I just toss it in the trash can.

ES project 1-6. Measure AC Voltage using a multimeter

Multimeter

(Volts AC)

+-

~+

-

AC Voltage

Symbol

BE proj 1-8

What can happen without a ground wire?

The ground wire protects against a short circuit

What have we learned so far?

• Electricity is a portable and useful form of energy that we can use to do work.

• Electricity consists Voltage and Current.

– Voltage is the measure of electromagnetic force that can cause electrons to flow through wires and electronic devices.

– Amperes is the measure of electron flow, called current, that provides energy used by electronic devices. The term Amperes is usually abbreviated as Amps.

• Most AC type electricity is generated at a power plant and delivered to electrical outlets by way of a distribution grid. This grid consists of transformers and wires.

• Because our bodies are good electrical conductors, accidental contact with conducting wires can shock or burn you. Accidents are much more likely if you do not understand how AC electricity works.

What if you accidentally touched both the black and white wires to your body?