Transcript
Page 1: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Electricity & MagnetismElectricity & Magnetism

Static, Currents, CircuitsStatic, Currents, Circuits

Magnetic Fields & Electro MagnetsMagnetic Fields & Electro Magnets

Motors & GeneratorsMotors & Generators

Page 2: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Atoms…Atoms…

Have Have neutronsneutrons, , protonsprotons, and , and electronselectrons..

Protons are Protons are positivelypositively charged chargedElectrons are Electrons are negativelynegatively charged charged

Page 3: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Electrons…Electrons…

Are located on the Are located on the outerouter edges of edges of atoms…they can be atoms…they can be movedmoved. .

A A concentrationconcentration of electrons in an of electrons in an atom creates a net atom creates a net negativenegative charge. charge.

If electrons are If electrons are strippedstripped away, the away, the atom becomes atom becomes positivelypositively charged. charged.

Page 4: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Electrons…Electrons…

Are located on the Are located on the outerouter edges of edges of atoms…they can be atoms…they can be movedmoved. . valencevalence

A A concentrationconcentration of electrons in an of electrons in an atom creates a net atom creates a net negativenegative charge. charge. anionanion

If electrons are If electrons are strippedstripped away, the away, the atom becomes atom becomes positivelypositively charged. charged.

cationcation

Page 5: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

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The world is filled with The world is filled with electrical electrical chargescharges::

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What is this electrical What is this electrical potentialpotential called?called?

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Page 7: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Static ElectricityStatic Electricity

The The build upbuild up of an electric charge of an electric charge on the on the surfacesurface of an object. of an object.

The charge builds up but The charge builds up but does does not flow.not flow.

Static electricity Static electricity is is potential potential energyenergy. It does . It does notnot move. It is move. It is storedstored..

Page 8: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Static DischargeStatic Discharge……

Occurs when there is a Occurs when there is a lossloss of of static electricity due to three static electricity due to three possible things:possible things:

FrictionFriction – rubbing ( – rubbing (direct contactdirect contact))ConductionConduction – – direct contactdirect contactInductionInduction – through an electrical – through an electrical field (field (not direct contactnot direct contact))

Page 9: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Electricity that Electricity that movesmoves……

CurrentCurrent: The flow of electrons : The flow of electrons from one place to another.from one place to another.

Measured in Measured in amperesamperes (amps) (amps)KineticKinetic energy energy

Page 10: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

How can we How can we controlcontrol currents? currents?

With With circuitscircuits..CircuitCircuit: is a : is a pathpath for the flow of for the flow of

electrons. We use electrons. We use wireswires..

Page 11: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

There are 2 types of currents:There are 2 types of currents:Direct Current Direct Current ((DCDC)) – Where – Where

electrons flow in the electrons flow in the samesame direction in direction in a wire. a wire.

The The devices you plug in to a walldevices you plug in to a wall

Page 12: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

2nd type of current:2nd type of current:

Alternating Current Alternating Current ((ACAC)) – electrons flow – electrons flow in in differentdifferent directions in a wire directions in a wire

The The current in buildings and housescurrent in buildings and houses

Page 13: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

There are 2 types of circuits:There are 2 types of circuits:

Series CircuitSeries Circuit: the components : the components are lined up along are lined up along oneone path. If path. If the circuit is broken, the circuit is broken, all all components turn off.components turn off.

Page 14: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Series CircuitSeries Circuit

Page 15: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

22ndnd type of circuit: type of circuit:

Parallel Circuit Parallel Circuit – there are – there are severalseveral branching paths to the components. branching paths to the components. If the circuit is broken at any one If the circuit is broken at any one branch, branch, only the components on only the components on that branch will turn offthat branch will turn off..

Most Most houses and buildings are houses and buildings are wired this waywired this way

Page 16: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Parallel CircuitParallel Circuit

Page 17: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Conductors vs. InsulatorsConductors vs. Insulators

ConductorsConductors – material through – material through which electric current flows which electric current flows easilyeasily..

InsulatorsInsulators – materials through – materials through which electric current which electric current cannot cannot movemove..

Page 18: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Conductors vs. InsulatorsConductors vs. Insulators

ConductorsConductors – material through – material through which electric current flows which electric current flows easilyeasily..

Conductor – makes music “flow” from the orchestraConductor – makes music “flow” from the orchestra Conductor – makes train “flow” smoothly down tracksConductor – makes train “flow” smoothly down tracks

InsulatorsInsulators – materials through – materials through which electric current which electric current cannot cannot movemove..

Page 19: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

ExamplesExamples

ConductorsConductors::MetalMetalWaterWater

InsulatorsInsulators::StyrofoamStyrofoamRubberRubberPlasticPlasticPaperPaper

Page 20: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

• SEMICONDUCTORS

• Semiconductors are materials that essentially can be conditioned to act as good conductors, or good insulators, or anything in between.

• Common elements such as carbon, silicon, and germanium are semiconductors.

• Can you find them on the Periodic Table? What do they have in common?

• Silicon is the best and most widely used semiconductor.

Page 21: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

DiodesDiodes

Diode device Diode device is a one way is a one way valve that valve that controls the flow controls the flow of of electricity – electricity – LEDLED lights are the lights are the

best examplebest exampleLED = Light Emitting DiodeLED = Light Emitting Diode

TransistorsTransistors are used to amplify are used to amplify electrical signals (like in a radio)electrical signals (like in a radio)

Page 22: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

What is What is ResistanceResistance??

The The oppositionopposition to the flow of an to the flow of an electric current, producing electric current, producing heatheat..

The The greatergreater the resistance, the the resistance, the lessless current gets through. current gets through.

GoodGood conductors have conductors have lowlow resistance.resistance.

Measured in Measured in ohmsohms..

Page 23: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

What Influences What Influences ResistanceResistance??

Material of wireMaterial of wire – aluminum and – aluminum and copper have low resistancecopper have low resistance

ThicknessThickness – the thicker the wire the – the thicker the wire the lower the resistancelower the resistance

LengthLength – shorter wire has lower – shorter wire has lower resistanceresistance

TemperatureTemperature – lower temperature has – lower temperature has lower resistancelower resistance

Page 24: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

What is What is VoltageVoltage??

The The measure of energymeasure of energy given to given to the charge flowing in a circuit.the charge flowing in a circuit.

The The greatergreater the voltage, the the voltage, the greater the force or “pressure”greater the force or “pressure” that drives the charge through the that drives the charge through the circuit.circuit.

Page 25: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Difference b/t Difference b/t Volts,Volts, Amps, Amps, & Ohms Ohms

Example – you could say that…Example – you could say that…Current (amps)Current (amps) measure measure how much water how much water

comes out of a water pipe. (comes out of a water pipe. (amountamount) ) Voltage (volts)Voltage (volts) measure measure how much how much

pressure pressure is behind the water. (is behind the water. (forceforce) ) Resistance (ohms)Resistance (ohms) measures the measures the frictionfriction

against the inside of the water pipe against the inside of the water pipe

Page 26: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators
Page 27: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Ohm’s LawOhm’s Law

Resistance = Voltage / CurrentResistance = Voltage / Current

Ohms = Volts / AmpsOhms = Volts / Amps

Page 28: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Practice with Practice with Ohm’s LawOhm’s Law

OhmsOhms VoltsVolts AmpsAmps

44 100100 2525

1515 150150 1010

22 3030 1515

99 4545 55

66 4848 88

Page 29: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Difference b/t Difference b/t voltsvolts & & wattswatts

If If volts x amps = watts volts x amps = watts Then Then force force of electricityof electricity

x x amountamount of electricity of electricity

how how powerfulpowerful it is it is

Remember,Remember, how much water?how much water?

P = w / tP = w / t how much time?how much time?

Page 30: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Properties of Properties of MagnetsMagnets

All magnets have two areas of strongest force, called All magnets have two areas of strongest force, called polespoles..

Each magnet has Each magnet has one one northnorth pole pole and and one one south south polepole.. Like poles repel, and opposite poles attract.Like poles repel, and opposite poles attract. The magnetic region where you can “feel the force” is The magnetic region where you can “feel the force” is

called a called a magnetic field.magnetic field.

Page 31: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Magnetic MaterialsMagnetic Materials

What makes some things What makes some things magnetic, while other things magnetic, while other things can’t be magnetized?can’t be magnetized?

Spinning electrons cause small Spinning electrons cause small magnetic fields around each magnetic fields around each atom.atom.

Magnetic materials have atoms Magnetic materials have atoms whose magnetic fields can be whose magnetic fields can be lined up in the same directionlined up in the same direction. .

Areas where atoms’ magnetic Areas where atoms’ magnetic fields line up are called fields line up are called magnetic magnetic domainsdomains..

magnetic domain magnetic domain

Randomly arranged domains =Randomly arranged domains = No magnetNo magnet!!

Magnetic domains lined up =Magnetic domains lined up = MagnetMagnet!!

Page 32: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

The Earth is a magnet!The Earth is a magnet!magnetic north polemagnetic north pole

geographic north polegeographic north pole

magnetic south polemagnetic south polegeographic south pole

geographic south pole

Magnetic lines of force around Magnetic lines of force around the earth are like the field lines the earth are like the field lines around a giant bar magnet. around a giant bar magnet.

The The magnetic north pole magnetic north pole and and the the geographic north pole geographic north pole are are not located in the same place!not located in the same place!

The north pole of a The north pole of a compasscompass points to the earth’s magnetic points to the earth’s magnetic north pole.north pole.

Page 33: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Electricity to MagnetismElectricity to Magnetism In 1820, H.C. Oersted In 1820, H.C. Oersted

discovered that an electric discovered that an electric current flowing through a wire current flowing through a wire had a magnetic field around it.had a magnetic field around it.

Electricity can cause Electricity can cause magnetismmagnetism!!

ElectromagnetsElectromagnets are powerful are powerful magnets that can be turned on magnets that can be turned on and off.and off.

You can make an You can make an electromagnet stronger by electromagnet stronger by

1.1. putting putting more turns more turns of wire in of wire in the coil the coil

2.2. making a larger making a larger iron coreiron core, ,

3.3. increasing theincreasing the current current through through the wire.the wire.

Page 34: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

What is an electromagnet?What is an electromagnet?

ElectromagnetElectromagnet – a magnet made – a magnet made from a from a current bearing coilcurrent bearing coil of wire of wire wrapped around an wrapped around an iron or steel iron or steel core. (ferromagnetic core)core. (ferromagnetic core)

SolenoidSolenoid – the coiled wire – the coiled wire that that gets wrapped around the core.gets wrapped around the core.

Page 35: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Uses for electromagnetsUses for electromagnets

A simple A simple DC electric motor DC electric motor contains a contains a permanent magnetpermanent magnet, an , an electromagnetelectromagnet, and a , and a commutator. When current flows commutator. When current flows through the electromagnet, it turns through the electromagnet, it turns within the magnetic field of the within the magnetic field of the permanent magnet, permanent magnet, changing changing electricity to mechanical energyelectricity to mechanical energy..

Current meters Current meters also use also use permanent magnets and permanent magnets and electromagnets. When current electromagnets. When current flows through a wire, it makes an flows through a wire, it makes an electromagnet. The force between electromagnet. The force between the electromagnet and the the electromagnet and the permanent magnet makes a permanent magnet makes a needle move on the meter.needle move on the meter.

Page 36: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Magnetism to ElectricityMagnetism to Electricity

Joseph Henry and Michael Joseph Henry and Michael Faraday discovered that Faraday discovered that magnetism could also magnetism could also produce electric currentproduce electric current. . Basis of Basis of alternating current. alternating current.

If a magnet is moved back and If a magnet is moved back and forthforth through a coil of wire, through a coil of wire, current can be made to flow current can be made to flow through the wire. This is the idea through the wire. This is the idea behind behind electric generators electric generators and and transformerstransformers..

Current moves left in wire. Current moves right in wire.

Page 37: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

Uses for Electromagnetic Uses for Electromagnetic InductionInduction

GeneratorsGenerators produce AC produce AC current for current for home and home and industrial useindustrial use. Water, wind, . Water, wind, or steam are used to move or steam are used to move large electromagnets through large electromagnets through the coils of wire to produce the coils of wire to produce current.current.

TransformersTransformers are used to are used to step up voltage step up voltage of electricity of electricity that must travel long distances that must travel long distances through wires. Other through wires. Other transformers then transformers then step down step down the voltagethe voltage before it enters before it enters our homes.our homes.

Page 38: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

What is a generator?What is a generator?

GeneratorGenerator – a machine that – a machine that changes mechanical energy to changes mechanical energy to electrical energyelectrical energy

Usually use Usually use movingmoving magnets to magnets to create create currentscurrents in coils of wire. in coils of wire.

Page 39: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

What is a motor?What is a motor?

MotorMotor – a device that – a device that changes changes electrical energy to mechanical electrical energy to mechanical energyenergy that can do that can do workwork..

Page 40: Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

That’s It !!!!That’s It !!!!


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