physical science goal 4 notes. brain pop: electricity hill.com/sites/0078802482/student_view0/...

Physical SciencePhysical ScienceGoal 4 NotesGoal 4 Notes

Brain Pop: ElectricityBrain Pop: Electricity

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ElectricityElectricity

Static electricity is the Static electricity is the build up of an electrical build up of an electrical charge. charge.

For electrically charged For electrically charged materials, opposites materials, opposites charges attract, while charges attract, while like charges repel.like charges repel.

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• Electricity is moving electrons.

ConductorsConductors allow electrons to move freely allow electrons to move freely through them.through them. Objects are grounded when they are Objects are grounded when they are

connected to the earth or ground by a good connected to the earth or ground by a good conductor.conductor.

InsulatorsInsulators are materials that do not allow are materials that do not allow electrons to move freely through them.electrons to move freely through them.

Voltage – Potential DifferenceVoltage – Potential Difference

The electrical potential is the potential The electrical potential is the potential energy difference per unit charge. energy difference per unit charge.

The potential difference is the difference in The potential difference is the difference in potential between two places. potential between two places. Units for potential difference are volts (V). Units for potential difference are volts (V).

Electrical Potential DifferenceElectrical Potential Difference


Potential difference can be referred to as Potential difference can be referred to as voltage and is measured with a voltmeter. voltage and is measured with a voltmeter.

Voltage is a comparison of the energy Voltage is a comparison of the energy

carried by electrons at different points.carried by electrons at different points.

CircuitCircuit Circuit is a closed path through which Circuit is a closed path through which

electrons flow. electrons flow.

Current is the flow of electrons through a Current is the flow of electrons through a wire or conductor. wire or conductor. Units for current are amperes (A) as is a Units for current are amperes (A) as is a

measure of the number of electrons passing a measure of the number of electrons passing a point in a given time.point in a given time.

BatteriesBatteries

A.A. Dry cell - Electron pump Dry cell - Electron pump with a potential difference with a potential difference between the positive and between the positive and negative terminals. negative terminals.

• Zinc container with a moist Zinc container with a moist chemical paste with a solid chemical paste with a solid carbon rod in the center. carbon rod in the center. The paste contains MnOThe paste contains MnO22

(manganese dioxide), (manganese dioxide), NHNH44Cl (ammonium chloride) Cl (ammonium chloride)

and C (carbon) which and C (carbon) which reacts with the zinc.reacts with the zinc.

B. Wet cell - Contain metal B. Wet cell - Contain metal plates placed in a plates placed in a chemical solution chemical solution (electrolyte).(electrolyte).

Ex.: Car battery – lead Ex.: Car battery – lead

storage battery. Plates storage battery. Plates of lead (Pb) and lead of lead (Pb) and lead dioxide (PbO2) in dioxide (PbO2) in sulfuric acid (Hsulfuric acid (H22SOSO44) ) solution. The car solution. The car battery has 6 cells with battery has 6 cells with a potential of 2 V each a potential of 2 V each for a total of 12 V.for a total of 12 V.

ResistanceResistance

Resistance is a Resistance is a materials ability to materials ability to oppose the flow of oppose the flow of electrons causing it to electrons causing it to change electrical energy change electrical energy into thermal energy and into thermal energy and in some cases light. in some cases light.

Resistance is measured Resistance is measured in ohms (Ω). in ohms (Ω).

Copper - low resistance

Tungsten - high resistance

All conductors, except superconductors at All conductors, except superconductors at very low temperatures, have some very low temperatures, have some resistance.resistance.

For a given material, resistance is For a given material, resistance is increased as length increases; decreases increased as length increases; decreases as thickness increases; and, usually as thickness increases; and, usually increases as temperature increases.increases as temperature increases.

Ohm’s LawOhm’s Law

Potential difference = current X resistancePotential difference = current X resistance

V = I RV = I R

UnitsUnits

V = potential differenceV = potential difference volts (V)volts (V)

I = currentI = current amperes (A)amperes (A)

R = resistanceR = resistance ohms (Ω)ohms (Ω)

Resistance and Ohm’s LawResistance and Ohm’s Law


• Voltage increases when current increases.

• Voltage decreases when resistance increases

Flash CardFlash Card

V = R

V

R

Ohm's Law Units

R - resistance (ohms)

I - current A (amperes)

V - voltage V (volts)

CircuitsCircuits


CircuitsCircuits

1.1. Series circuit – only one path for the Series circuit – only one path for the electricityelectricity

2. Parallel circuit – More than one path for 2. Parallel circuit – More than one path for the electricity with each branch having the electricity with each branch having the same potential difference.the same potential difference.

3. Complex circuit – contains both series 3. Complex circuit – contains both series circuits and parallel circuitscircuits and parallel circuits

Series Series CircuitsCircuits

Parallel Parallel CircuitsCircuits

3. Open circuit – when a switch is opened 3. Open circuit – when a switch is opened (turned off) or a bulb burns out the current (turned off) or a bulb burns out the current no longer flows through that path, no longer flows through that path, therefore the circuit is open. therefore the circuit is open.

4. Closed circuit – when a switch is closed 4. Closed circuit – when a switch is closed (turned on) and bulbs burn the current (turned on) and bulbs burn the current flows through the path (s), therefore the flows through the path (s), therefore the circuit is closed.circuit is closed.

Safety DevicesSafety Devices Fuses and circuit breakers are safety devices Fuses and circuit breakers are safety devices

to prevent a circuit from overheating and to prevent a circuit from overheating and causing a fire. causing a fire.

Fuses have a metal strip that melts when the Fuses have a metal strip that melts when the circuit gets too hot, causing the circuit to circuit gets too hot, causing the circuit to open. open. Fuses can only be used once and must be Fuses can only be used once and must be

replaced with the same size and type of fuse. replaced with the same size and type of fuse. Fuses can explode if they get too hot and cause Fuses can explode if they get too hot and cause

fires.fires.

FusesFuses

BreakersBreakers

Circuit breakers contain a metal strip that Circuit breakers contain a metal strip that bends as it heats up and trips the breaker bends as it heats up and trips the breaker switch to open the circuit. switch to open the circuit. Breakers can be reset several times before Breakers can be reset several times before

they have to be replaced. they have to be replaced. Like fuses breakers come in different sizes.Like fuses breakers come in different sizes.

Main breakers control the flow of electricity Main breakers control the flow of electricity into the house. into the house. When they are thrown (or tripped) there will When they are thrown (or tripped) there will

be be nono electricity in the house or building. electricity in the house or building.

BreakersBreakers

Electrical PowerElectrical PowerElectrical power is the rate at which electric energy Electrical power is the rate at which electric energy

is converted into another form of energy.is converted into another form of energy.Electric Power = current X voltageElectric Power = current X voltage

PPEE = I V = I V

UnitsUnitsPPEE = electric power = electric power watts (W) or kWwatts (W) or kWI = currentI = current amperes (A)amperes (A)V = voltageV = voltage volts (V)volts (V)

One watt of electric power is produced when One watt of electric power is produced when one ampere of current flows through a circuit one ampere of current flows through a circuit with a potential difference of one volt.with a potential difference of one volt.


P = I V

P

V

E

E

Electrical Power Units

V - voltage V (volts)

I - current A (amperes)

P - electrical power W (watts)E

Electrical EnergyElectrical EnergyElectrical Energy is calculated by multiplying the Electrical Energy is calculated by multiplying the

electrical power by the amount of time the power electrical power by the amount of time the power was used.was used.

Energy = power X timeEnergy = power X timeE = P tE = P tUnitsUnits

E = electrical energyE = electrical energy kilowatt-hours (kWh)kilowatt-hours (kWh)P = electrical powerP = electrical power kilowatt (kW)kilowatt (kW)t = timet = time hours (h) hours (h)

One kilowatt-hour (kWh) is 1000 watts of One kilowatt-hour (kWh) is 1000 watts of power used in one hour.power used in one hour.


Electrical Energy Units

t - time h

P - electrical power kW

E - Electrical energy kWh

E = P t

E

tP


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Brain Pop: MagnetismBrain Pop: Magnetism

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MagnetsMagnets

Magnets point north – south when Magnets point north – south when suspended from a string and align with the suspended from a string and align with the Earth’s magnetic north and south poles.Earth’s magnetic north and south poles.

Magnetism is a force of attraction and Magnetism is a force of attraction and repulsion between like and unlike poles.repulsion between like and unlike poles.

Magnetic poles are at the ends and are Magnetic poles are at the ends and are the area of strongest attraction.the area of strongest attraction.

Permanent magnets retain their properties Permanent magnets retain their properties for a long time and are made of iron (Fe), for a long time and are made of iron (Fe), nickel (Ni) or cobalt (Co). nickel (Ni) or cobalt (Co). Magnetite is a mineral with natural magnetic Magnetite is a mineral with natural magnetic

properties. properties. Lodestone is a natural magnet.Lodestone is a natural magnet.

Magnetism can be conducted through paper Magnetism can be conducted through paper clips and nails to make temporary magnets. clips and nails to make temporary magnets. Temporary magnets lose the magnetic properties Temporary magnets lose the magnetic properties

after being removed from the magnet.after being removed from the magnet.

Magnetic FieldsMagnetic Fields

Magnetic field is the area around a magnet Magnetic field is the area around a magnet where the magnetic forces act. where the magnetic forces act.

They are strongest near the poles.They are strongest near the poles.

The Earth’s magnetic north pole is near The Earth’s magnetic north pole is near the south pole and the Earth’s magnetic the south pole and the Earth’s magnetic south pole is near the north pole.south pole is near the north pole.

Magnetic DomainsMagnetic Domains In order to form a magnet, the magnetic In order to form a magnet, the magnetic

poles of the atoms must align. poles of the atoms must align.

Magnetic domains are groups of atoms Magnetic domains are groups of atoms with aligned magnetic poles. with aligned magnetic poles. Permanent magnets can lose their domains if Permanent magnets can lose their domains if

heated or dropped. heated or dropped. When a permanent magnet is cut into smaller When a permanent magnet is cut into smaller

pieces, each piece will have its own poles.pieces, each piece will have its own poles.

Compass is an instrument for determining Compass is an instrument for determining direction that contains a magnetized direction that contains a magnetized needle to point to the Earth’s magnetic needle to point to the Earth’s magnetic poles.poles.

1820, Hans Christian Oersted, Danish 1820, Hans Christian Oersted, Danish physics teacher, observed that current physics teacher, observed that current passing through a wire produced a passing through a wire produced a magnetic field that could be detected by a magnetic field that could be detected by a compass, and that the direction of the compass, and that the direction of the magnetic field reversed when the direction magnetic field reversed when the direction of the electric current reversed.of the electric current reversed.

ElectromagnetsElectromagnetsElectromagnets are strong temporary magnets Electromagnets are strong temporary magnets

produced by inserting an iron core into a coil produced by inserting an iron core into a coil of wire and passing an electric current of wire and passing an electric current through the wire. through the wire.

Strength of electromagnets can be changed Strength of electromagnets can be changed by changing the number of coils in the wire by changing the number of coils in the wire or the amount of current going through the or the amount of current going through the wire. wire.

Uses for electromagnetsUses for electromagnets: loudspeaker, : loudspeaker, doorbells, lifting metal objects, meters, toys, doorbells, lifting metal objects, meters, toys, and motors.and motors.

GalvanometersGalvanometers

Galvanometer is an instrument used to Galvanometer is an instrument used to detect electrical current.detect electrical current. Ammeter is a galvanometer that measures Ammeter is a galvanometer that measures

current and is connected in series in the current and is connected in series in the circuit.circuit.

Voltmeter is a galvanometer that measures Voltmeter is a galvanometer that measures potential difference and is connected in potential difference and is connected in parallel in the circuit.parallel in the circuit.

Electromagnetic inductionElectromagnetic induction 1831, Michael Faraday, British scientist, 1831, Michael Faraday, British scientist,

and Joseph Henry, American scientist, and Joseph Henry, American scientist, working independently found that by working independently found that by moving a wire in and out of a magnetic moving a wire in and out of a magnetic field that they could produce an electric field that they could produce an electric current.current. Electromagnetic induction is the production of Electromagnetic induction is the production of

an electrical current by moving a wire through an electrical current by moving a wire through a magnetic field.a magnetic field.

GeneratorsGenerators

Generators produce electricity by rotating a Generators produce electricity by rotating a loop of wire in a magnetic field. loop of wire in a magnetic field.

The wire loop is rotated by a mechanical The wire loop is rotated by a mechanical energy source. energy source.

This produces alternating current because This produces alternating current because the current changes direction each time the current changes direction each time the wire passes a different pole.the wire passes a different pole.

Turbines are large wheels that rotate when Turbines are large wheels that rotate when pushed by water, wind, or steam. pushed by water, wind, or steam.

The steam can be produced by burning of The steam can be produced by burning of fossil fuels or nuclear reactions.fossil fuels or nuclear reactions.

Types of CurrentTypes of Current

DC – direct current flows in one directionDC – direct current flows in one direction

AC – alternating current reverses the AC – alternating current reverses the direction of flow in a regular patterndirection of flow in a regular pattern In the US, our current has a frequency of 60 In the US, our current has a frequency of 60

Hz and changes direction 120 times/sec.Hz and changes direction 120 times/sec.

TransformersTransformers

Transformers reduce or increase voltage of Transformers reduce or increase voltage of alternating current. alternating current.

Transformers contain 2 coils of wire (primary Transformers contain 2 coils of wire (primary coil – incoming current and secondary coil coil – incoming current and secondary coil – outgoing current) wrapped around an – outgoing current) wrapped around an iron core.iron core.

2 Types of Transformers2 Types of Transformers

Step-up transformers have more coils of Step-up transformers have more coils of wire on the secondary coil and increase wire on the secondary coil and increase the voltage.the voltage.

Step-down transformers have more coils Step-down transformers have more coils of wire on the primary coil and decrease of wire on the primary coil and decrease the voltage.the voltage.

SuperconductorsSuperconductors

1911, Heike Kamerlingh Onnes, a Danish 1911, Heike Kamerlingh Onnes, a Danish physicist, discovered that at low physicist, discovered that at low temperatures some materials lose their temperatures some materials lose their electrical resistance.electrical resistance.

Since the material loses its electrical Since the material loses its electrical resistance at low temperatures it is called resistance at low temperatures it is called a superconductor.a superconductor.

The temperature at which the The temperature at which the superconductor loses its electrical superconductor loses its electrical resistance is its critical temperature. resistance is its critical temperature.

Most of these temperatures are near Most of these temperatures are near absolute zero -273 °C. absolute zero -273 °C.

Liquid helium (4.2 K or -268.2 °C) was Liquid helium (4.2 K or -268.2 °C) was used to cool the first superconductors.used to cool the first superconductors.

1987, J.G.Bednorz and K.A.Müller 1987, J.G.Bednorz and K.A.Müller produced a superconductor from a produced a superconductor from a ceramic material with a critical ceramic material with a critical temperature of 30 K (-243 °C).temperature of 30 K (-243 °C).

We now have superconductors with critical We now have superconductors with critical temperatures at 130 K (-143 °C) and use temperatures at 130 K (-143 °C) and use liquid nitrogen (-196 °C) to cool the liquid nitrogen (-196 °C) to cool the material because it is cheaper.material because it is cheaper.

Superconductors are more efficient Superconductors are more efficient because they do not lose energy due to because they do not lose energy due to resistance. resistance.

Research continues to build Research continues to build superconductor that is less brittle and superconductor that is less brittle and more flexible and thinner.more flexible and thinner.

Floating trains: Fact or Fiction?Floating trains: Fact or Fiction?

Using superconductors for the rails and Using superconductors for the rails and magnet in the bottom of the train can magnet in the bottom of the train can cause the train to levitate (float) above the cause the train to levitate (float) above the rails.rails. + No Friction, No Pollution, Reduced Energy + No Friction, No Pollution, Reduced Energy

WasteWaste Air resistance still exist, Environment can still Air resistance still exist, Environment can still

have an effect.have an effect.

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