Electricity and Magnetism
• This is what we have discovered so far.
• There is no theme for this because these
should be in your notes already.
• If you don’t have it in your notes then you
better hurry to write it down.
Magnetism
• All magnets have two poles. North and South.
– You cannot separate a magnet into just one pole.
• Magnets exert a force (attract and repel).
– Non-metallic items are not attracted nor repelled
– Not all metals are attracted nor repelled.
• Magnets can work through objects.
– Magnets can attract or repel through non-magnetic materials, ie your desk,
hand, plastic, etc.
• Magnets vary in size shape and color but that does not matter to
determine the strength of the magnet.
– A small magnet can have a higher strength than a larger magnet
• Magnets have a field that surrounds them.
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–
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The field goes from North to South poles.
This is the area that exerts the force.
The larger the separation in lines the less magnetic force.
The further away from a magnet the less the force.
Electricity
• The information in black font is what should
be written in your notebooks from the
presentations.
• The red font indicates new information.
• All of the presentations had to do with one
type of electricity.
– Current electricity
• Current electricity is the continuous flow of electric
charge.
• There are two types of current electricity.
Current Electricity
• You investigated the flow of electricity through
a system.
– The system contained wires, resistors, and a
power source.
• In order for energy to flow the system has to
be complete.
Two Ways for Energy to Flow
1. Alternating current:
– Abbreviated AC
– This type of current can alternate directions.
• This is what type of current is in our homes, schools, businesses,
etc.
• In your experiments you may have noticed that when you
connected the positive side of one battery to the positive side
of another the light wouldn’t light.
2. Direct current:
– This current can only flow in one direction.
• Flashlights, cell phones, computers, etc. all run on direct current.
That’s why you have the big plug to convert AC to DC.
Parts needed for Energy to flow
• Power source
• Wires
That is all you need for energy to flow.
That is the simplest circuit.
Energy flows from the negative to the positive.
But how can you tell energy is flowing?
Energy Flow Slowed
• Many of you discovered that the light bulbs
will light up, fans will spin, bell will ring, and
sound can be made when connected to the
power source.
• With relation to the light bulbs you noticed
that the bulbs did not light up the same. They
were all different brightness. Even if you
added more power they became brighter but
not all the same brightness.
Resistors
• Each item in the circuit other than the power
source will resist the flow of energy.
– Resistors – oppose the flow of energy.
– The wire and the items in the circuit are all
slowing down the flow of energy.
• So by the time the energy reached the last
bulb it was reduced so much that there wasn’t
enough to produce the same light.
Wires as a Resistor
• An experiment proved that the longer the wire the more the
resistance to flow, the shorter the wire the less resistance to flow.
This was evidenced by the light bulb being brighter for a shorter
wire compared to dimmer for longer wires.
• Not only is length a factor to increase resistance but so is thickness.
The thinner the wire the more resistance to flow. The thicker the
wire the less resistance to flow.
• Finally, the temperature of the wire can aid in resistance. The cooler
the wire the less resistance to flow. The warmer the wire the more
resistant to flow.
• Items in the system can slow down flow as well; the fan, lights,
bells, anything connected to the wire aids in slowing down the flow.
All are considered resistors.
In Summary
• We have proven that current electricity is the
flow of energy from a power source through a
system and that flow must return back to the
power source.
• We have also shown that items in the system
can reduce the flow of the energy.
Conductors and Insulators
• Another thing that you proved in your experiments is
that there are items that help the flow of electricity.
• Conductors – material that charge can easily flow
through.
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Metals make very good conductors.
Metals are made of ions with free electrons.
We know electrons are a charged particle.
The electrons move freely along the metal.
• That means electricity is the movement of electrons.
Conductors and Insulators
• You also showed that there are some
materials that electrons (electric charge)
cannot flow through.
• Insulators – materials that charge (electrons)
cannot easily flow through.
– These materials do not have free electrons so the
energy cannot flow.
– Most materials are insulators.
Types of Circuits
• Many of you showed that we need to connect one end
of a battery to another in order to create a circuit.
• Circuit – Complete path for energy to flow from a
power source and return to the power source.
– Many discovered that your light wouldn’t light unless you
connected back to the same battery.
– Or if there was an opening in the circuit.
– Or if the light bulb was broken.
• All of the above represent a “break” in the circuit.
• Any break in the system stops the flow of electrons.
Beneficial Breaks
• Can you think of a time when I would
intentionally want to break the system?
• Switches – intentionally break the system to stop
the flow of electrons.
• But how do I install a switch to turn something off
without turning off all items in the system?
– Kinda like the demonstration lights.
– Or the lights in the class. Why don’t all devices turn
off when I flip the switch?
Two Types of Circuits
• You may have noticed in some of the experiments
that it all depends on how you wire the circuit.
• The only way items will work in the circuit is if
there is a path for the flow of electrons. The
electrons pass through the system, through the
object and power the object. Right?
• Break the system anywhere along that flow and
the electrons cannot return to the source. So, no
power to the objects. There are two ways to get
power to objects.
Series Circuits
• Charge (electrons) have only one path to flow.
• All items are connected one after the other.
• If one object in a series circuit stops working
then they all stop.
• Each object also increases the resistance so by
the time electrons reach the last object the
flow is decreased.
• If a break occurs anywhere along the circuit
the flow stops and all objects stop working.
Series Circuit Diagram
Wires
Power Source
There are
two
batteries
shown here
Resistors – Light
bulbs, fans, TVs,
radios, Refrigerators,
stoves, etc.
Electron Flow
The red arrows show the path the electrons take through the circuit. Notice how
there is only one way for the electrons to flow.
Parallel Circuits
• Charge (electrons) have more than one path to
flow.
• Items in the circuit can be connected one after
another or on a separate path.
• If one object in a parallel circuit stops it may not
affect how another object works.
• The objects still have resistance but the same
energy is allowed to flow to the objects.
• If a break occurs anywhere along the circuit the
flow stops only for that section. Depending on
where the break is.
Parallel Circuit Diagram
You will see many of the same parts to a parallel circuit as you will a series
circuit. There is a power source (two again in this diagram), there are wires, and
three resistors. The difference is the way the electrons can flow. Look at the
path the electrons can flow through the system.
The electrons can
move from the
source back to the
source along this
path.
They can also move from the source
back to the source using this path
Electrons can
also travel along
this path to the
source
All paths
deliver the
same amount
of energy.
Powering all
objects the
same.