Electricity and Electricity and CircuitsCircuits

Lesson 28

GPSGPS

S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. • b. Demonstrate the advantages and

disadvantages of series and parallel circuits and how they transfer energy.

What is Electricity?What is Electricity?

ElectricityElectricity is generated from the is generated from the motion of tiny charged atomic motion of tiny charged atomic particles called electrons and particles called electrons and protons!protons!

Protons = +Protons = + Electrons = -Electrons = -

electron

neutron

proton

Nucleus

Energy Levels

What is Electricity?What is Electricity?

Electrons orbit the Electrons orbit the nucleus of an atom at nucleus of an atom at different distances often different distances often referred to as levels. referred to as levels. Each “energy level” Each “energy level” contains a particular contains a particular number of electrons at number of electrons at its maximum. Electrons its maximum. Electrons in different energy levels in different energy levels can jump from one atom can jump from one atom to another. These jumps to another. These jumps change the overall change the overall charge of the atoms. The charge of the atoms. The changes result in changes result in electricity.electricity.

Nucleus

electron

neutron

proton

Energy

Levels

Electric CurrentElectric Current

Electric currentElectric current is the flow of is the flow of electric charges.electric charges.

Electric current is measured in Electric current is measured in amperesamperes (A), of amps. (A), of amps.

Electric chargesElectric charges will always flow will always flow from a region of higher potential from a region of higher potential energy to a region of lower energy to a region of lower potential energy.potential energy.

Electric CurrentElectric Current

Even though the current, voltage, and Even though the current, voltage, and resistance vary from circuit to circuit, resistance vary from circuit to circuit, there is often a simple relationship there is often a simple relationship among them. This relationship is among them. This relationship is Ohm’s Ohm’s lawlaw..

Ohm’s lawOhm’s law states that the current (I) in states that the current (I) in a wire is equal to the voltage (V) a wire is equal to the voltage (V) divided by the resistance (R).divided by the resistance (R).

Current (I) = Voltage (V)/Resistance (R)Current (I) = Voltage (V)/Resistance (R)

Electric Current Electric Current

The difference in The difference in potential potential energyenergy between two locations is between two locations is know as know as potential differencepotential difference..

Potential differencePotential difference results from results from differences in the differences in the electrical electrical chargecharge in two locations. in two locations.

Electric Current Electric Current

Potential difference is called Potential difference is called voltagevoltage and is measured in units and is measured in units called called voltsvolts (V).(V).

A battery is a device that converts A battery is a device that converts chemical energy into electricity.chemical energy into electricity.

In batteries the potential energy In batteries the potential energy difference is created by the difference is created by the positive and negative terminals. positive and negative terminals.

Circuits Circuits

A A circuit circuit is a path through which is a path through which electricity can flow. electricity can flow.

Charges will flow in a circuit when Charges will flow in a circuit when there is potential difference. there is potential difference.

Circuits Circuits

A circuit may also have a A circuit may also have a switchswitch that can be open, which stops the that can be open, which stops the flow of current, or closed, which flow of current, or closed, which allows current to flow.allows current to flow.

Energy flows only through a Energy flows only through a circuit that is closed.circuit that is closed.

Circuits Circuits

Energy SourceEnergy Source• A circuit needs an A circuit needs an energy sourceenergy source to to

push a charge through the circuitpush a charge through the circuit• A battery creates a potential A battery creates a potential

difference between its negative and difference between its negative and positive terminalspositive terminals

• Electric charges are repelled by Electric charges are repelled by negative terminal and attracted negative terminal and attracted toward the positive terminal.toward the positive terminal.

Circuits Circuits

LoadsLoads• A A loadload is a device in a circuit that is a device in a circuit that

operates using electrical energy.operates using electrical energy.– Examples of loads are light bulbs, Examples of loads are light bulbs,

bells, radios, and motors. bells, radios, and motors.

Circuits Circuits

ConductorsConductors• A A conductorconductor is a material that allows is a material that allows

electrical energy to flow through it electrical energy to flow through it easily.easily.– Metals make good conductors, so wires Metals make good conductors, so wires

from metals are most often the from metals are most often the conductors in circuit.conductors in circuit.

Circuits Circuits

ResistorsResistors• A A resistor resistor is an object added to a is an object added to a

circuit that restricts the flow of circuit that restricts the flow of electrical energy.electrical energy.– Resistors inhibit the flow of electric Resistors inhibit the flow of electric

current by producing a voltage drop current by producing a voltage drop when current passes though them.when current passes though them.

– Resistors can be used to produce a Resistors can be used to produce a desired potential differencedesired potential difference

– They limit current and cause some They limit current and cause some electric energy to be give off as heat.electric energy to be give off as heat.

Circuits Circuits

SwitchSwitch• A A switchswitch is a device that is used to control the is a device that is used to control the

flow of current through a circuit.flow of current through a circuit.• A switch works by separating (open) or A switch works by separating (open) or

bringing together (closed) two conductors bringing together (closed) two conductors attached to the circuit. attached to the circuit.

• When a switch is open, the path is broken, so When a switch is open, the path is broken, so not electricity flows through the circuitnot electricity flows through the circuit

• When a switch is closed, it creates a When a switch is closed, it creates a continuous path through which an electric continuous path through which an electric charge can flow. charge can flow.

Series Circuits Series Circuits

A A series circuitseries circuit is a is a circuit that provides circuit that provides only one possible only one possible path for the flow of path for the flow of current.current.

In a series circuit, In a series circuit, the loads are set up the loads are set up in a series, or line, in a series, or line, that requires current that requires current to flow through one to flow through one load before passing load before passing through the next.through the next.

Parallel Circuits Parallel Circuits

A A parallel circuitparallel circuit offers offers more than one path for more than one path for the flow of electricity.the flow of electricity.

Each load in a parallel Each load in a parallel circuit has its own circuit has its own closed circuit pathway closed circuit pathway to the energy source.to the energy source.

Loads in a parallel Loads in a parallel circuit uses the full circuit uses the full voltage of the energy voltage of the energy source. source.

Electricity and MagnetismElectricity and Magnetism

Lesson 29Lesson 29

GPSGPS

S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. • c. Investigate and explain that

electric currents and magnets can exert force on each other.

Magnetic forceMagnetic force is a push or pull is a push or pull that is exerted by a magnet.that is exerted by a magnet. • A magnet has two polesA magnet has two poles

– North & SouthNorth & South

MagnetsMagnets

MagnetsMagnets

– Poles that are alike repel or push apartPoles that are alike repel or push apart– Poles that are unalike attract or pull Poles that are unalike attract or pull

togethertogether

The area surrounding a magnet in The area surrounding a magnet in which the magnetic force exists is which the magnetic force exists is called the called the magnetic field.magnetic field.

MagnetsMagnets

In the 1800’s, a Danish scientist named Hans Oersted discovered that passing a current through a piece of wire caused a magnetic field to form around the wire.

The production of a magnetic field by electric current is called electromagnetism.

MagnetsMagnets

A magnet that is made by passing an electric current through a coil of wire wrapped around an iron core is called an electromagnet.

MagnetsMagnets

An electromagnet consists of an iron core placed inside a wire coil. The magnetic field strength of a wire coil carrying an electric current increases in direct proportion to the number of turns of the coil.

MagnetsMagnets

Uses of ElectromagnetsUses of Electromagnets

Changing the Strength of an Changing the Strength of an ElectromagnetElectromagnet

To Increase To Increase StrengthStrength

To Decrease To Decrease StrengthStrength

Increase strength of Increase strength of currentcurrent

Decrease strength of Decrease strength of currentcurrent

Add more coils of wireAdd more coils of wire Use fewer coils of wireUse fewer coils of wire

Increase size of iron Increase size of iron corecore

Decrease size of iron Decrease size of iron corecore

Uses of ElectromagnetsUses of Electromagnets

An An electric motorelectric motor is a device that is a device that transforms electrical energy into transforms electrical energy into mechanical energy.mechanical energy.

Washers and dryers are two Washers and dryers are two appliances that operate using appliances that operate using motors.motors.

Uses of ElectromagnetsUses of Electromagnets

A A generatorgenerator is a device that is a device that transforms mechanical energy into transforms mechanical energy into electrical energy.electrical energy.

The electrical systems of many The electrical systems of many cars use electricity produced by cars use electricity produced by generators to work. generators to work.

THE END