ELECTRICITY

Part 1: Overview and Electrostatics.

Exam # 1 was

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• One of the three basic energy use sectors.• We will study all aspects of generating

electricity, but first and overview and some basic physics.

Electric Power Generation1950-2005

Table 1.1. Net Generation by Energy Source: Total (All Sectors), 2002-December 2012

(Thousand Megawatthours)

Period CoalPetroleum

LiquidsPetroleum

CokeNatural

GasOther

Gas Nuclear

Hydroelectric

Conventional

OtherRenewable

Sources

Hydroelectric

PumpedStorage Other Total

Annual Totals

2002 1,933,130 78,701 15,867 691,006 11,463 780,064 264,329 79,109 -8,743 13,527 3,858,452

2003 1,973,737 102,734 16,672 649,908 15,600 763,733 275,806 79,487 -8,535 14,045 3,883,185

2004 1,978,301 100,391 20,754 710,100 15,252 788,528 268,417 83,067 -8,488 14,232 3,970,555

2005 2,012,873 99,840 22,385 760,960 13,464 781,986 270,321 87,329 -6,558 12,821 4,055,423

2006 1,990,511 44,460 19,706 816,441 14,177 787,219 289,246 96,525 -6,558 12,974 4,064,702

2007 2,016,456 49,505 16,234 896,590 13,453 806,425 247,510 105,238 -6,896 12,231 4,156,745

2008 1,985,801 31,917 14,325 882,981 11,707 806,208 254,831 126,101 -6,288 11,804 4,119,388

2009 1,755,904 25,972 12,964 920,979 10,632 798,855 273,445 144,279 -4,627 11,928 3,950,331

2010 1,847,290 23,337 13,724 987,697 11,313 806,968 260,203 167,173 -5,501 12,855 4,125,060

2011 1,733,430 16,086 14,096 1,013,689 11,566 790,204 319,355 193,981 -5,905 14,154 4,100,656

2012 1,517,203 13,209 9,691 1,230,708 11,212 769,331 276,535 218,787 -4,658 12,466 4,054,485

Graph

Have you studied Electricity before this class?

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Electrostatics

• Study of charges that are NOT moving.• What is Charge?• A new property of matter. Similar to mass.• Mass creates and responds to gravitational

fields• Charges create and respond to electric fields.• (Moving charges generate and respond to

magnetic fields….more later)

• There are two types of charges: positive (+) and negative (-).

• Common symbols for charge are q and/or Q.• Rubber/fur and glass/silk demo

• Units of charge: Coulomb (C)• A Coulomb is a lot of charge. Usually deal in

micro coulombs and less in electrostatics.• Fundamental charge: Magnitude of the charge on

an electron or proton.»e=1.6x10-19C

• Like charges repel, Unlike charges attract.• Van de Graff demo 1

Definitions

• Conductor: Material that charges are free to move around in. Examples: metal (silver is best but copper is almost as good)

• Insulator (Dielectric): Material that charges are NOT free to move around in. Examples: glass, quartz, wood.

• Semiconductor: Can behave as either depending on conditions: Silicon, Germanium, Gallium-Arsenide.

• Van de Graff demos continued

Forces on electric charges

• Gravitational force on a mass:»F=mg

• Electric force on a charge:»F=qE

• E: electric field =F/q is the force per unit charge that a given charge experiences. (vector)

• Note: In general E changes in space and time.

• If we move a charge in an electric field, we do work on it.

• W =Fd =qEd• Define Voltage as V=Ed (Not exact, but it will

do.)• Note V=W/q: work done per unit charge in

moving it through an electric field. (Or potential energy per unit charge.)

• Equivalent to raising mass up in a gravitational field.

UNITS OF E & V

• V=PE/q (Joule/Coulomb=Volt)

• E =F/q (Newton/Coulomb) OR• E=V/d (Volt/meter)

CAPACITOR

• Device for storing charge• Two conductors

separated by an insulator.

• Battery moves charge from one plate to another.