Demos

►Electrostatic Motor►Large Capcitor and Quarters (small

scale lightening rod)►Light Bulb Board►Nichrome Wire►Hot-dog cooker►12V battery and bulb vs. 120V bulb►Vinegar Battery

Electrical EnergyElectrical Energya)a) Easy to GenerateEasy to Generate

b)b) Easy to TransmitEasy to Transmit

c)c) Can be 100% renewable and non-Can be 100% renewable and non-polluting.polluting.

d)d) Easy to change into different Easy to change into different forms of energy.forms of energy.

11 Heating ElementsHeating Elements

22 Motors (Rotational Kinetic Energy)Motors (Rotational Kinetic Energy)

33 Lighting and other E&M WavesLighting and other E&M Waves

44 Sound Waves (e.g. speakers)Sound Waves (e.g. speakers)

55 Actuators (electrical signals used to Actuators (electrical signals used to actuate something mechanically)actuate something mechanically)

Electricity►Anything dealing with

stationary or moving Electric Charge

►Electric Charge can be either negative (i.e. the electron) or positive (i.e. the proton in the nucleus of the atom)

►Electron has a charge of -1

►Proton has a change of +1

Proton has 2000X the mass of the electron.

Electricity…Electricity…prior to 18prior to 18thth-century people -century people

experienced static electricity experienced static electricity and naturally occurring and naturally occurring

electricity (lightening) but electricity (lightening) but didn’t understand it.didn’t understand it.

In 1663 a device similar to the Van de Graph generator seen in lab was created.

Ben Franklin’s Kite Ben Franklin’s Kite ExperimentExperiment

Ben Franklin thought the sparks from Ben Franklin thought the sparks from static electricity looked a lot like static electricity looked a lot like lightning. lightning.

A metal key was attached to the kite’sstring. The key was attached to a Leyden Jar via a small wire.

It is unlikely Franklin ever did thelegendary experiment becauseother people who tried the experiment had fatal results.

The installation of Lightening Rods to protect tall buildings camefrom Franklin.

ElectricityElectricity

► Static Electricity is Static Electricity is charge that builds charge that builds up in one place.up in one place.

► Non-static electricity Non-static electricity is the movement of is the movement of negatively charged negatively charged particlesparticles

► Electrons are Electrons are negatively charged negatively charged particlesparticles

► Unlike charges Unlike charges attract, like charges attract, like charges repelrepel

Franklin’s Static Electric MotorFranklin’s Static Electric Motor

Electrons hitch-hike on the thimbles to Electrons hitch-hike on the thimbles to neutralize the + side, thus making the neutralize the + side, thus making the rotor spin around.rotor spin around.

http://f3wm.free.fr/sciences/jefimenko.html

What is a electrical What is a electrical conductor?conductor?

► A material that allows electrons to flow A material that allows electrons to flow freely. Most metals are good electrical freely. Most metals are good electrical conductors. Outer electrons are loosely conductors. Outer electrons are loosely bound to the metal atoms, therefore they bound to the metal atoms, therefore they can roam freely. can roam freely. “Cloud of Electrons”“Cloud of Electrons”

► A material that strongly resists the flow of A material that strongly resists the flow of electrons is an insulator. Most non-metals electrons is an insulator. Most non-metals are good insulators.are good insulators.

► A semiconductor can be made into a A semiconductor can be made into a conductor or an insulator. It’s electrical conductor or an insulator. It’s electrical properties can be precisely controlled with properties can be precisely controlled with added impurities.added impurities.

Unit of Charge

►Coulomb►1C = 6 Billion, Billion

electrons►6.241506 x 1018 electrons

Electrical forces are Electrical forces are much greatermuch greater than than gravitational forces. Gravity is always gravitational forces. Gravity is always

an attractive force, but electrical forces an attractive force, but electrical forces can be both attractive or repulsive.can be both attractive or repulsive.

http://www.glenbrook.k12.il.us/gbssci/phys/Class/estatics/u8l3b.html

1 lb is about 4.4 Newtons

Electrostatic forces can be Electrostatic forces can be stronger than the force of stronger than the force of

gravity.gravity.

www.wfu.edu/physics

Electrical Force is 1040 times stronger that gravitational

attraction.

+_

Examples of Electrical Forces

►Chemical Bonding►Forces that keep materials

together►Burning Gas►Energy in a Spring►Friction

Why don’t we notice these electrical forces if they are so

large?

►Most large objects are electrically neutral

►Gravity is more noticeable because there is only one kind of mass.

+

__

_

_

____

_+

+

+

+

++ +

+

Static ChargeStatic Charge

When a bunch of negative particles When a bunch of negative particles are separated from positive particles are separated from positive particles (missing electrons), an electrostatic (missing electrons), an electrostatic force is created. This is force is due to force is created. This is force is due to a a charge imbalancecharge imbalance..

http://www.tpub.com/neets/book10/39i.htm

Van De Graph Generator Van De Graph Generator produces static chargeproduces static charge

Photocopier ProcessPhotocopier Process

http://www.howstuffworks.com/photocopier1.htm

Photocopier Drums are light sensitive.This photoconductive material becomes conductive when in light, but not conductive in the dark.Charge can leave the drum where light hits the drum. Charge remains in the areas where light did not shine.

http://www.howstuffworks.com/photocopier1.htm

Xerographic Copies use Xerographic Copies use electrostatic charge to produce electrostatic charge to produce

& transfer images& transfer images► A document image is projected onto a A document image is projected onto a

rotating photoconductor drum. An image rotating photoconductor drum. An image identical to the original black and white is identical to the original black and white is produced with charged particles on the produced with charged particles on the drum. drum.

►Oppositely charged toner adheres to the Oppositely charged toner adheres to the charged portion of the photoconductor.charged portion of the photoconductor.

► A charged piece of paper makes contact A charged piece of paper makes contact with the photoconductor and the toner with the photoconductor and the toner image is transferred to the paper.image is transferred to the paper.

► The paper is then heated and the toner is The paper is then heated and the toner is fused onto the paper.fused onto the paper.

http://www.sciam.com/article.cfm?id=how-does-a-photocopier-wo

Chester Carlson Chester Carlson Physicist, Engineer, & Patent Physicist, Engineer, & Patent

LawyerLawyer

►Develops the electrophotography process in Develops the electrophotography process in 19381938

► Acquires patents for the processAcquires patents for the process► Seeks investors from IBM, RCA, General Seeks investors from IBM, RCA, General

Electric, and the US ArmyElectric, and the US Army► Finally in 1944 convinces Haloid Co. that Finally in 1944 convinces Haloid Co. that

idea has commercial viability.idea has commercial viability.► Process is coined XeroX, and Haloid Co. Process is coined XeroX, and Haloid Co.

changes its name to Xerox and begins changes its name to Xerox and begins selling copiers in 1950selling copiers in 1950

► Plain Paper copies come out in 1959; sales Plain Paper copies come out in 1959; sales surge along with Xerox’s revenuesurge along with Xerox’s revenue

What is electric What is electric current?current?

I = charge/timeI = charge/timeI = I = Coulombs/secCoulombs/sec

Electrons are moving through conductors such as Electrons are moving through conductors such as wires.wires.

If the electrons flow at a constant rate and always flow If the electrons flow at a constant rate and always flow in the same direction, we say it is in the same direction, we say it is DC (direct current)DC (direct current)..If the electrons periodically change direction, the If the electrons periodically change direction, the current is current is AC (alternating current)AC (alternating current)..

Flow of Electrons

Unit of Current:Unit of Current: 1 Amp = 1 Coulomb/sec. 1 Amp = 1 Coulomb/sec.

When do we get current?

►Cloud of Electrons in conductors respond to an Electric Field.

►An Electric field is similar to a gravitational field.

►Mass responds to gravity►Electrons respond to an Electric Field►The Electric Field Potential is

measured in Volts

The amount of Electric Field needed to move electrons in a wire depends

on…

►How much current we want►The resistance of the material that

the electrons have to travel through

Ohm’s LawOhm’s Law

V = IRV = IRV – voltage is electrical force that V – voltage is electrical force that causes causes electrons to flowelectrons to flow

I - Current is the flow rate of electronsI - Current is the flow rate of electrons

R – Resistance to electron flowR – Resistance to electron flow

Voltage Potential

1 jolt = 1 joule/1 coulomb

Current in the Nichrome wireCurrent in the Nichrome wire

Electrical Energy is converted into light and heat by passing current through a resistive wire.

Three things are needed to make an electric circuit:

►Voltage Potential►A closed loop►A device or load

http://www.energyquest.ca.gov

http://www.windows.ucar.edu

PowerPower

P = V I (watts = Joules/sec)P = V I (watts = Joules/sec)

P – Power is the rate of work being doneP – Power is the rate of work being done

(units are watts, horsepower, etc.)(units are watts, horsepower, etc.)

V – Voltage (J/C)V – Voltage (J/C)

I – Current (C/sec)I – Current (C/sec)

P X time = Energy (KWH, BTU, Joules, P X time = Energy (KWH, BTU, Joules, Calories)Calories)

Recall James Joule from the famous paddle wheel experiment in the Thermodynamics section.

To perform work, a To perform work, a continuous continuous flow of charge is requiredflow of charge is required

Some kind of device or system is needed to produce a continuous flow of charge.

Luigi Galvani’s conducts experiments with Luigi Galvani’s conducts experiments with “animal electricity” using frogs’ legs“animal electricity” using frogs’ legs

Applying static electricity to dissected frogs’ legs Applying static electricity to dissected frogs’ legs caused the legs to twitch. (c. 1780)caused the legs to twitch. (c. 1780)

Luigi Galvanihttp://itp.nyu.edu

Two metals causing legsTo twitch.www.karisteeves.net

Galvani hanging froglegs on brass hooks.www.hgs.k12.va.us

Galvani later laid frog legs out on brass Galvani later laid frog legs out on brass hooks that were hooked onto an iron lattice hooks that were hooked onto an iron lattice during a thunderstorm. The frog legs during a thunderstorm. The frog legs continued to twitch after the storm.continued to twitch after the storm.

Alessandro Volta and the Alessandro Volta and the BatteryBattery

A battery using copper and zinc, interleaved with cardboard soaked in brine (a good electrical conductor).

Volta presented in 1800 the world’s first device that coulddeliver continuous current.

http://ieee-virtual-museum.org

Wikipedia

An electrochemical cell has three main An electrochemical cell has three main parts: two dissimilar metals and an parts: two dissimilar metals and an electrolyte. The electrolyte allows ions electrolyte. The electrolyte allows ions and electrons to move between the and electrons to move between the two metals. By creating a closed path, two metals. By creating a closed path, electrons will flow and electricity can electrons will flow and electricity can be delivered to a device.be delivered to a device.

http://sxxz.blogspot.com

The Carbon and Zinc dry-cell The Carbon and Zinc dry-cell batterybattery

First demonstrated in 1866.First demonstrated in 1866.This is a chemical reaction where electrons This is a chemical reaction where electrons are exchanged between two metals, are exchanged between two metals, causing continuous current through a load. causing continuous current through a load.

Wikipedia

Lead Acid Battery ReactionsLead Acid Battery Reactions

Pb + SOPb + SO44²¯ → PbSO²¯ → PbSO44 + 2e- + H+ + 2e- + H+

The reduction potential of this reaction is The reduction potential of this reaction is +0.356 Volts. +0.356 Volts.

PbOPbO22 + SO + SO44²¯ + 4 H+ + 2e- → PbSO²¯ + 4 H+ + 2e- → PbSO44 + H + H22OO

The potential of this reaction is 1.685 volts.The potential of this reaction is 1.685 volts.

Total voltage created is about 2V.Total voltage created is about 2V.

Lead Acid batteries provide high current,Lead Acid batteries provide high current,and are rechargeable, making themand are rechargeable, making themeffective for starting cars.effective for starting cars.

http://sxxz.blogspot.com/2005/03/how-do-batteries-work.html

►The Sciences- 5eThe Sciences- 5e, Trefil and Hazen, Trefil and Hazen►A History of Great InventionsA History of Great Inventions, James , James

DysonDyson► InternetInternet

Text SourcesText Sources