Electric Energy

- "electricity" occurs when electrons flow

 

Electromagnetism FLASHCARDS

Electromagnetism TEST REVIEW SHEET

NEW Electromagnetism Review Sheet ANSWERS

 

Print the lyrics to Electricity, Electricity and use it as a study guide for the chapter!

 

The 4 fundamentals of electrostatics
1. Like charges REPEL like charges
2. Opposite charges ATTRACT
3. Positive protons do not move out of the nucleus
4. Negative electrons CAN and DO move

 

The Law of Electric Charges: opposite charges attract; like charges repel

Neutrons DO NOT repel or attract because they have no charge.

Protons repel protons

(but they are stuck together in the nucleus. Here's why

Electrons

repel other electrons.

Protons (+) and electrons (-)

will attract!

This is the foundation for an electric circuit. Without opposite charges, electrons would have no reason to move around.
PLAY ELECTRIC FIELD HOCKEY to remind yourself of the Law of electric charges while having some fun

Static Electricity

Static electricity occurs when friction seperates charges.

Some materials hold on to electrons tightly and other hold on to electrons more loosely. Electrons can be ripped away and cause a difference in charges.

(Examples: fuzzy bunny slippers on the carpet, fur on PVC pipe, balloon on sweater, etc)

 

The negative electrons build up in one place and will DISCHARGE to a place that is positive.

PLAY JOHN TRAVOLTAGE

Friction in the atmosphere is what causes lightning to strike. Negative charges in the clouds are attracted to the positively charged ground.

WARNING: This cartoon , though a cute idea, has a problem with it. Can you find something that is wrong?

As the cartoon was suggesting, Lighting is the result of friction in the atmosphere. Check out this video on lightning.

 

2009

A teenage girl survived a terrifying lightning strike after she was saved by the wire of her iPod. Schoolgirl Sophie Frost and her boyfriend Mason Billington, both 14, stopped to shelter under a tree when a storm struck as they were walking near their homes.

Doctors believe Sophie survived the 300,000-volt surge only because it travelled through the gadget’s wire, diverting it away from her vital organs.

 

Both are expected to make a full recovery and Sophie may not even have a permanent scar. She will be thankful she was wearing her iPod, which she had been given four days earlier as a gift from her grandmother.

Returning from hospital yesterday after three days of treatment, she said: ‘I’m just glad to be alive. I don’t remember a thing about what happened, but from what everyone tells me it’s a miracle I’m still here.

‘Everybody’s said the iPod must have diverted the lightning away from my body, which probably saved my life. I’ve got a few burns, but it’s all healing OK.’

Sophie and Mason were knocked unconscious by the lightning bolt while holding hands and taking shelter in a field on Monday night.

Mason came round and carried Sophie, who was scorched and unconscious, to a nearby road where he flagged down a female motorist who took the couple to Southend hospital.

Sophie suffered burns to her body and legs, some temporary damage to her eyes and a perforated eardrum. 

Dr Ian Cotton, a reader in electrical engineering at Manchester University, said Sophie could have been saved by her iPod. ‘If lightning hits a person it can do one of two things. It can go down the outside of the skin, which is more likely if someone is caught in a storm and their body is wet. ‘Or it can puncture the skin and go into the body. Potentially a metal wire, which is highly conductive could divert the electricity away from the heart and save someone’s life.’

 

Sophie was reunited with her boyfriend and family in Rayleigh, Essex, yesterday after being transferred to the Broomfield Hospital for burns treatment.

She said Mason, whose eyesight is now back to normal, was a hero. ‘My mum thinks he’s wonderful,’ she added.

 

A Van DeGraaff generator is used to store up negative charges. It does this by forcing a rubber belt over a felt wheel next to a metal dome conductor. The dome is now charged and looking for positive places to discharge to (aka a shock).
 
Witness the largest VanDeGraaff generator in the world!
 
A few years back, the concession stand at Francis Howell North's football field was struck by lightning. Here is the security camera footage of that event.

 

CURRENT ELECTRICITY

The flow of electrons in a circuit.

 

Current occurs when electrons move from the negative terminal to the positive terminal. In a battery it is between two chemicals. Electrons "want" to travel to the positive source on the battery. If we want lights to turn on and electric motors to run, we place the lights and motors in the path of the electron. It's like an obstacle courses for the electron on their way to the other side of the battery.

It reminds me of water that "wants" to fall over a cliff and turns a wheel on it's way down. Electrons do "work" for us in a circuit.

 

 

A circuit has three basic parts:

source

 

A battery or generator will supply the electrons that are needed to flow.

 

wire

 

Electrons must have a path to flow through the circuit. Copper is the most common conductor to use for wire. Silver and Gold would be great but they are too expensive to use practically.

 

load

 

Anything that transforms electrical energy into other forms of energy.

Anything that DOES WORK is a LOAD.

 

Electrons are ONLY able to flow within a CLOSED circuit.

This means that there are no gaps in the wire.

Electrons will not flow in an OPEN circuit.

This means there is a gap in the wire and electrons cannot find their way to the positive terminal.

We use a SWITCH to open and close circuits. (like the drawbridge below allowing cars to move)

Comparing electricity to flowing water can be very helpful.

 

 

Voltage can be thought of as "electrical pressure".

Imagine getting a drink of water from a fountain or garden hose. The pressure is low. The water flows to the end of the hose but it isn't in any hurry to get there. If the water was electricity and the hose, a wire, we would say the circuit had "low voltage".

 

Now hook a fire hose up to the water fountain. If you tried to take a drink it would rip your face off! increased pressure makes the water move down the hose quickly and allows it to travel a long distance after it leaves. Again, if we were discussing electricity we would say this is "high voltage"

 

Voltage can be thought of as "electrical potential"

Imagine some water at the top of Dragon Falls in Venezuela. It has a great deal of potential energy at the top and If allowed to, would fall straight down to the pool below and do it FAST.

If electrons had the potential to move LIKE the water has the potential to fall down Dragon Falls, we would say the electrons have a "high voltage". A GREAT desire to move!

Now imagine the same amount of water but this time with much less potenial in a small creek. The water is still flowing downhill, but because it is nearly flat, the water just trickles by. In this comparison, this would be considered "low voltage".

Water will not flow on a flat surface. It needs potential to fall.

Electricity will not flow without a difference in voltages. It needs electrical potential to flow!

VOLTAGE is the "pressure" that makes electrons flow in a circuit.

 

 

Voltage is the pressure that makes electrons flow in a circuit.

The voltage of a battery depends on the chemicals used to make it.

A common battery is basically made up of two types of chemicals. One chemical that loves to get rid of its electrons...

.

...and one loves to take electrons.

These two would spark an instant friendship if brought together!

Unfortunately if they came in contact with each other the electricity would be short lived. It is called a SHORT CIRCUIT.

Using a battery, WE decide how often the electrons flow between chemicals. The chemicals are separated from each other inside a battery and can be connected by the wires in a circuit.

Chemical energy is transformed into electricity when electrons are moved . The more the electrons want to move the greater the VOLTAGE.

 

Common Voltages
AAA, AA, C, D batteries
1.5 Volts
"6 Volt" battery
6 Volts
"9 Volt" battery
9 Volts
car battery
12 Volts
Metrolink-type train
600-750 Volts

shock from a taser

Don't worry, Dr. Pinkham wasn't being arrested. This was part of his police corps training
50,000 Volts

shock from Van de Graaff generator

 

350,000 Volts

high Voltage power lines

 

500,000 Volts

 

CURRENT, measured in Amperes (Amps) describes how many electrons pass by in a given amount of time.

 

Continuing with the water/electricity analogy, imagine that you are sitting next to a river that has almost run dry. In fact it is only a trickle of water. We might suggest that there is only a little bit of water passing by you in any given second. The current would be low . When a relatively few number of electrons pass by while in a circuit we say the current (amperage) is low.

Now it rains and the little trickle turns into a flash flood in the riverbed. The amount of water that passes by you each second goes up. Similarly, when more electrons are found traveling past a point we say the current in the circuit is high.

common Amperages (DC)
Hearing aid
0.7 mA
Human body can feel the electricity
1 mA
Causes muscle contractions that cannot be relaxed
10 mA
taser gun
100 mA
Can cause cardiac arrest (death)
300-500 mA
Headlamp (car)
5000 mA (5 A)
starter Motor (car)
8000-16000mA (8-16 A)

Volts may sound dangerous but it's really the Amps that kill!

The nails on the right MELT with only 2 Volts of pressure but over 900 Amps of current. This is called a SHORT CIRCUIT. The current is high because the resistance is low. Notice what happens to the Amps when the nails get hot.

 

 

 

Electrons slow down or stop moving when there is RESISTANCE.

Electrical resistance is measured in Ohms.

A high amount of Ohms (resistance) makes it difficult for electrons to flow through a wire.

We use the greek letter Omega to represent Ohms

You'll need to know 3 basic fundamentals about resistance.

It is EASIER for electrons to travel through...

1) ...cold wires rather than hot wires.

Remember that particles speed up and spread out when heated.

Electrons in a hot wire must travel a greater distance to get to the next particle.

2) ...short wires rather than long wires.

It is easier to travel short distances rather than long ones.

3)...thick wires rather than thin wires.

Thick (low gauge) wires are like 8 lane superhighways for electrons. There is plenty of room for the flow of many electrons. Thin (high gauge) wires are more like one lane gravel roads. It is a much more difficult pathway to travel.

Electrons have less resistance to flow in thick wires.

Wires heat up when electricity flows through them.

 

Electrons flowing in a wire is FRICTION which causes it to heat up. Too much resistance will cause more friction and add heat as well.

 

Substances can either CONDUCT or INSULATE electricity

In general, metals are fantastic conductors of electricity while clothing, glass, plastics, and other synthetic materials are good insulators .

CONDUCTORS - allow electrons to flow through easily

INSULATORS - resist electrons flowing through them easily

Circuits can be wired together as SERIES or PARALLEL

This is a series circuit. The voltage is divided evenly (shared)between each of the lights.

ex) a 9 volt battery with 3 lights will give 3 volts to each light.

So if you add another light, ALL of the lights will be dimmer.

If one light goes out, the circuit is broken (OPEN) and ALL of the lights go out.

 

This is a PARALLEL circuit. Each light has its own path to and from the battery.

Each light should receive the full voltage of the battery. Adding another light will make little difference.

Each load recieves the same voltage as the source.

 

If one light goes out, the rest of the strand will stay lit.

Which circuit would be best to wire your house with? Why?

HOMEWORK: Play with the circuit builder below

 

 

Magnetism - the other side of electricity

Magnetism and electricity are married with no chance of divorce. It comes down to a pair of simple true statements to understand...

1. Whenever electrons flow down a wire, a magnetic field is generated.

 

2. When a magnet is moved in a coil of copper wire...electricity is generated.

 

 

Practice the application of these principles with this REALLY COOL simulation.

Make sure you try each of the tabs at the top.

 

Remember "opposites attract"? It still works here too!

North will repel North. South will repel South.

North attracts South

Examples from class discussion include...

bar magnets
 
ring shaped magnets
 
Mag-Lev train

Mr.Freeze at Six Flags

A great idea to launch supplies across space. Right now it's just science fiction.

 

 

 

 

The Earth's Magnetosphere (Magnetic Field)

The core of the earth is molten magnetic material. This flowing magnetic liquid forms a magenetic field around the earth that protects us from harmful solar radiation. Watch this demonstrator from YouTube.

 

Ferrofluid Sculptures

this Iron-rich liquid changes shape when the magnetic field around it is changed.

   
   

 

ENERGY

BASICS

Heat

Electro - magnetic

Mechanical

Nuclear

Sound

 

 

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