Electricity magnetism
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Electricity & Magnetism. Universal Forces Throughout all galaxies far, far away………. Remember, FORCES exert a push or pull on objects and can do WORK They can act over a distance without touching Gravitational force – a weak force due to mass

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Electricity & Magnetism

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Electricity magnetism

Electricity & Magnetism


Universal forces throughout all galaxies far far away

Universal ForcesThroughout all galaxies far, far away………

  • Remember, FORCES exert a push or pull on objects and can do WORK

  • They can act over a distance without touching

    • Gravitational force – a weak force due to mass

    • Electromagnetic force – a stronger force due to charged particles

      • ELECTRICITY

      • MAGNETISM


What is a charge

What is a charge?

  • All matter is made up of atoms

  • All atoms are made up of :

    • Protons (+)

    • Neutron ( 0)

    • Electrons (-)

  • Electrons extremely SMALL mass

    • travels extremely FAST

    • has A LOT of KINETIC energy !


What is a charge1

What is a charge?

  • Atoms are normally NEUTRAL because:

    # of PROTONS = # of ELECTRONS

  • Electrons can move easily between objects

  • When an object LOSES electrons  positively charged

    # of PROTONS > # of ELECTRONS

  • When an object GAINS electrons  negatively charged

    # of PROTONS < # of ELECTRONS

  • This movement of electrons can transfer energy and do WORK.


Check for understanding what would occur to make a positive or negative particle

Check for UnderstandingWhat would occur to make a positive or negative particle?

+

-

-

+

+

+

-

-

+

+

-

-

-

NEGATIVE

POSITIVE


Law of charges

Law of Charges

  • Like charges REPEL or PUSH (+ and +) OR ( - and -)

  • Unlike charges ATTRACT or PULL (+ and - )

  • FORCE is exerted by electric charges!


Check for understanding would the following repel or attract each other

Check for Understanding:Would the following repel or attract each other?

  • REPEL

  • ATTRACT

  • REPEL

-

-

and

-

+

and

+

+

and


Electricity magnetism

  • Electrons (-) push each other away

  • Electrons (-) are pulled toward protons (+) or other positively charged objects


Induction

Induction

  • Some objects that really have an equal amount of charges, can temporarily shift their electrons so that an area may become more positive or negatively charged.


Static electricity

Static Electricity

  • Charges that build up is called static electricity.

    • Pollution control systems to capture smoke particles

    • Photocopiers, speakers, microphones

    • Lightning

    • Muscle cells

    • However, in general, static electricity is a nuisance!

    • Van der Graaf and Rockin’ Bill Nye


Static discharge

Static discharge

  • Discharge is a sudden movement of electrons

    • Unpredictable

    • Unreliable

    • Its just not really useful.

  • Static discharge occurs when a new path forms between two areas of opposite charge.

  • The electrons move suddenly to try to restore the balance between charged areas.


Pair share how would you explain getting shocked by the doorknob

Pair Share:How would you explain getting “shocked” by the doorknob?


Electric current

Electric Current

  • Static discharge is brief and limited in the number of electrons it moves.

  • To do USEFUL WORK, we need a continuous flow of charge.

  • This is an electric current.


Electric current cont

Electric Current, Cont.

  • For an Electric Current, we need…

  • A steady supply of moving electrons

  • A path for the electrons to follow and return to be reused.

  • Something to “push” the electrons along the path.


Water analogy

Water Analogy

  • Water in a high reservoir (PE) causes a downward force through pipes to a lower reservoir.

  • The higher the reservoir, the higher the PE.

  • Water flows through pipes in a continuous path. Higher reservoir creates flow with more KE.

  • Water is pumped back up to the higher reservoir to be re-used.


The electric circuit

The electric circuit…

  • Electrons “flow” along a closed path with no breaks.

  • Battery chemicals provide the “push” of electrons, acting as a “pump”. (ELECTRICAL FORCE )

  • The “strength” of the battery provides the PE of the circuit.

Work is done as electrons flow through a circuit .


Circuit construction

Circuit Construction

  • pHet Circuit Construction interactive


Let s talk numbers

Let’s talk numbers!

  • A battery is a device that converts chemical energy to electrical energy.

  • In a battery , one terminal (end) is Positive and the other terminal (end) is Negative.

  • The PE of the electrical flow of electrons from one end to the other is the voltage of the battery.

  • Higher voltage = Higher “push” of electrons through the circuit (Joules/Coulomb)


Let s talk numbers1

Let’s talk numbers!

  • Coulomb (C)

    • Is a bunch of electrons (6.25X 1018 electrons)

      6,250,000,000,000,000,000 electrons

  • 1 Volt is the PE that can move 1 Coulomb of charge using 1 Joule of energy

  • Ampere(amps) is 1 Coulomb in one second ( C / s)


What if we add a water wheel

What if we add…a water wheel ?

  • A wheel would hinder the flow – like friction.

  • Water uses some of it’s energy to make the wheel turn (work)

  • Water flows on through the wheel to continue the flow.

  • More than one wheel could be put into the flow of water.


Resistors

Resistors

  • Resistor = any object or substance that slows down the flow of electrons.

  • Electrons transfersome of their Kinetic energy when going through a resistor, so this is a place of energy conversion:

    • Light bulb  light energy

    • Heating element  thermal energy

    • Speaker  sound energy

  • Resistance measured in ohms. (Ω)


  • A short circuit

    A short circuit:

    • Resistors also protect a circuit from becoming a SHORT CIRCUIT!

    • Too much current!!

    • Wires get HOT!

    • Plastic covering can melt.

    • Fire may start.

    • Drains battery fast – or flips protective circuit breakerin electrical panel.


    Stop here

    Stop Here


    Magnetism

    Magnetism

    • Early discovery of natural occurring lodestones

      • they always oriented themselves north when floated on a piece of wood on water and

      • they concentrated iron shavings

    • There are Naturally occurring magnets and Man-made magnets.

    • Current science understands magnets to ALWAYS have a NORTH and a SOUTH pole, no matter how many times you divide a magnet(Di-Pole)


    Effects of magnetism

    Effects of Magnetism

    • Magnetic fields show the strength and direction of magnetic forces.

      • Closer lines = more strength

      • Force lines point from north pole to south pole

    • Same poles REPEL

    • Opposite poles ATTRACT

    • Effects of magnetism is very similar to the effects of static electrical charges.


    Magnetism from electricity

    Magnetism from Electricity

    • Magnets attract only a small group of materials.

      • Iron, nickel, cobalt, steel

    • We can INDUCE magnetism in some materials, especially iron.

    • A wire carrying a current that is coiled around a metal core strengthens the magnetic field.

    • The more coils, the STRONGER the magnetic field (lab!)

    • Electromagnets = magnets created by use of electric current.

    Li nk


    Electricity from magnetism

    Electricity from Magnetism

    • Does this work the other way around?

    • YES! If a magnet is moved through a coil of wire, a current is produced in the wire.

    • pHet Faraday interactive


    Electricity magnetism

    • What did you notice about the current flow?

    • The current only flows when the magnet is moving! When the magnet stops moving, so does the current.

      • The magnet PULLS the electrons along through the wire.

      • The more quickly the magnet moves, the faster the electrons move, SO….more current.

      • Remember… current is more electrons per second

        • More work is being done!


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