ELECTRICITYELECTRICITY

Part 1: Electrostatics.Part 1: Electrostatics.

►One of the three basic energy use One of the three basic energy use sectors.sectors.

Fuel Source for Electricity Fuel Source for Electricity 70% Fossil Fuel70% Fossil Fuel

Electric Power GenerationElectric Power Generation1950-20051950-2005

ElectrostaticsElectrostatics

►Study of charges that are NOT moving.Study of charges that are NOT moving.►What is What is ChargeCharge??►A new property of matter. Similar to A new property of matter. Similar to

mass.mass.►Mass creates and responds to Mass creates and responds to

gravitational fieldsgravitational fields►Charges create and respond to electric Charges create and respond to electric

fields.fields.

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

►Common symbols for charge are q and/or Common symbols for charge are q and/or Q.Q.

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

in micro coulombs and less in in micro coulombs and less in electrostatics.electrostatics.

►Fundamental charge: Magnitude of the Fundamental charge: Magnitude of the charge on an electron or proton.charge on an electron or proton.

►e=1.602 x 10e=1.602 x 10-19-19 C C►Like charges repel, Unlike charges attract.Like charges repel, Unlike charges attract.

Who discovered there are two types of Who discovered there are two types of electric chargeelectric charge??

1.1. John AdamsJohn Adams

2.2. Robert MilikanRobert Milikan

3.3. Ben Franklin Ben Franklin

4.4. ThalesThales

Who discovered the size of a Who discovered the size of a fundamental charge?fundamental charge?

1.1. Robert MilikanRobert Milikan

2.2. Ben FranklinBen Franklin

3.3. Alessandro Alessandro VoltaVolta

DefinitionsDefinitions

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

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

► SemiconductorSemiconductor:: Can behave as either Can behave as either depending on conditions: Silicon, depending on conditions: Silicon, Germanium, Gallium-Arsenide.Germanium, Gallium-Arsenide.

Forces on electric chargesForces on electric charges

►Gravitational force on a mass:Gravitational force on a mass:►F=mgF=mg

►Electric force on a charge:Electric force on a charge:►F=qEF=qE

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

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

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

►W =Fd =qEdW =Fd =qEd►Define Voltage as V=Ed Define Voltage as V=Ed ►Note V=W/q: work done per unit Note V=W/q: work done per unit

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

►Equivalent to raising mass up in a Equivalent to raising mass up in a gravitational field.gravitational field.

UNITS OF E & VUNITS OF E & V

►V=PE/q (Joule/Coulomb=Volt)V=PE/q (Joule/Coulomb=Volt)

►E =F/q (Newton/Coulomb)E =F/q (Newton/Coulomb)

OROR►E=V/d (Volt/meter)E=V/d (Volt/meter)

CAPACITORCAPACITOR

► Device for storing Device for storing chargecharge

► Two conductors Two conductors separated by an separated by an insulator.insulator.

► Battery moves Battery moves charge from one charge from one plate to another.plate to another.