# Presentation: 185374

## Charge! Electricity and Magnetism

- Michael Cooke
- Rice University
- Amber Johnson
- Fermilab

## What is Charge?

**Notes:**
You'll notice that some slides are really a sequence that builds up to a final, completed slide.  This is to help facilitate discussion without giving away all of the answers up front.

Ask the audience what “charge” is.  Take a few answers, asking the audience if they agree with each other's answers and if they have anything to add to someone else's reply.

## What is Charge?

- When atoms don't have as many electrons as they do protons, they carry a charge!
- How do they ACT?

**Notes:**
Talk about how everything is made up of atoms, but that usually the atoms are neutral, and there are just as many electrons as there are protons.

Then ask the audience how charged objects act, specifically how like and unlike charges act around each other.

## What is Charge?

- When atoms don't have as many electrons as they do protons, they carry a charge!
- Opposite charges attract
- Like charges repel

**Notes:**
Various electric fields are shown.  

On the left, a lone (positive) charge.  Discussing what electric field lines really are is optional, but field lines could be described as showing which way and how quickly a positive charge would accelerate if placed somewhere in the field.

In the center, two opposite charges, which attract each other.

On the right, two like (positive) charges, which repel each other.

## Where have YOU seen charge?

- “Stuck” charges are also called “Static Electricity”...
- Everyday examples are:
- ?
- ?
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- ?

**Notes:**
Mention that a charge buildup is also called “static electricity”, then ask the audience where they've seen charge before.

## Where have YOU seen charge?

- “Stuck” charges are also called “Static Electricity”...
- Everyday examples are:
- Socks in the dryer
- Walking around in your socks on carpet
- Getting out of the car in winter
- Lightening!

**Notes:**
More examples of static electricity include:- Getting shocked after using a sliding board- Taking off a sweater- Running a plastic comb or brush through your hair

Lightening is the discharge of a huge static buildup in the atmosphere.

## Charge in Action!

- We need some volunteers!
- We have some balloons and some string...
- Can you show us how like charges repel?
- How can you test for charge? (Electroscope!)
- We also have some wool and plastic...
- What things get attracted to a static charge?
- Are you surprised at what does & does not?

- _[Balloon Demo](file:///C:/Program%20Files/PhET/simulations/balloon/webstart.jnlp)_

**Notes:**
Demonstrations:

Use two balloons that are tied together by a long string.  Show that when holding the center of the string and letting them hang, they will touch each other.  When you give them a charge and let them hang by the center of the string, they will repel each other.

Use the wool on the PVC pipe and see what objects get picked up (remember what got picked up for later when using magnets to pick things up...)

You can use the electroscope before and after charging something to show that it has built a charge.  You can also show that items picked up by the balloons/PVC do not carry a charge.

Hit the “Balloon Demo” link to bring up a Java demo:Rub the balloon on the sweater to show it pick up charge.  Release the balloon from the middle of the screen to show the opposite charges on the sweater and balloon attract.  Take your time to show the way the wall polarizes when the balloon comes near it, and discuss that this is why the balloon will stick to (or pick up) neutral objects.

## Electricity is Moving Charge!

- How can we make charges move?

**Notes:**
Discussion could lead to many answers.  A voltage difference is the “physical” answer for why charges move, but likely either batteries or wall outlets will come up.

## Electricity is Moving Charge!

- How can we make charges move?
- We need a volunteer!
- We have some lemons, copper, zinc and a clock
- Can you make the clock work?

**Notes:**
The “Two Potato Clock” demonstration, only using lemons instead of potatoes.  Audience members tend to ask to keep the produce at the end of the session—we chose to go with lemons to try and discourage this!  Since the copper and zinc aren't usually sanitized before this demo, we never let people keep the lemons later...

Usually, we hand the student all the parts and ask them to confirm that the clock is not working.  If they don't know what to do, asking the audience to help them figure it out usually does the trick.  It takes both lemons to make the clock work, using the basic kit.

## Electricity is Moving Charge!

- How can we make charges move?
- We need a volunteer!
- We have some lemons, copper, zinc and a clock
- Can you make the clock work?
- This is a chemical generator!
- What are some other examples of chemicals creating electricity?

**Notes:**
The lemon acid (an electrolyte) reacts with the metals (the electrodes), stripping electrons from the copper and adding them to the zinc.  This makes the copper the positive terminal of the lemon battery, and the zinc the negative terminal. 

While each lemon might manage to produce the good part of a Volt on their own, they can't provide much current.  So, while the lemon batteries can make the clock work, they couldn't light a light bulb.

The obvious example of a chemical generator is a battery (a word you've probably already used to describe the lemon circuit!).  There are a lot of types of batteries...

## Batteries!

**Notes:**
Top left – Batteries like you might use in a toy or flashlight

Lower left – A car battery, which provides a LOT of current!

Lower right – Cell phones use rechargeable batteries

Top right – Various laptop batteries

## More ways to make electricity...

- Not all of our electricity comes from batteries...
- We need another volunteer!
- We want to light a light bulb...

**Notes:**
This demonstration uses the hand crank generator to light a light bulb.  Ask your volunteer how bright they can make the light shine!

## More ways to make electricity...

- Not all of our electricity comes from batteries...
- We need another volunteer!
- We want to light a light bulb...
- This is a mechanical generator
- What other mechanical generators can you think of?

**Notes:**
The most common mechanical generator is a power plant, although many other examples are possible.  Backup generators are usually mechanical generators that run on gasoline.  Discuss that this is the way the electricity to run your house is usually made.

One form of generating electricity that is not directly discussed in this presentation is the solar panel, which uses the photoelectric effect to generate electricity.  If this comes up, discuss that it can be used for certain situations, but that, in general, it provides a low current (which may get stored in a battery instead of directly used), and it's dependent on having a sunny day!  Panels can also be expensive.  These reasons are why most houses don't run using solar panels.

## Power Plants!

**Notes:**
Top left – A coal power plant

Lower left – A geothermal power plant

Lower right – A hydroelectric power plant (specifically, the Hoover Dam)

Upper right – A nuclear (fission) power plant

Center – The turbines inside the Hoover Dam

Missing are examples of wind and solar power plants, although they get mentioned in a later slide dealing with magnetsim...

## Circuits

- Electricity needs to flow from high voltage to low voltage
- Moving electricity is called CURRENT

**Notes:**
You could discuss voltage in many ways.  If you imagined electricity as flowing water, then a voltage difference is like a hight difference between two buckets.  Flowing water between the buckets is like an electric current.  If the buckets are at the same height, no current will flow.

In this example, a battery, which creates a voltage difference, is like a water pump that forces water to go from a lower bucket to a higher bucket.

## Circuits

- Electricity needs to flow from high voltage to low voltage
- Moving electricity is called CURRENT
- A lot of current can be

** **
**A lot of current can be**** dangerous!**

**Notes:**
A large voltage isn't necessarily a problem (as you can show later with the Van de Graaff generator), but a large amount current is!  Large amounts of current can make things very hot, make batteries explode, and it can literally stop your heart!

## Circuits

- Electricity needs to flow from high voltage to low voltage
- Moving electricity is called CURRENT
- A lot of current can be dangerous!
- If there's a break in a circuit, current won't flow!
- There are “open,” “closed” and “short” circuits
- Help us make some circuits!

**Notes:**
Open circuits are not completely connected, so no current can flow.

Closed circuits connect a high voltage to a low voltage, and allow current to flow.

Short circuits can be dangerous, because they can allow large amounts of current to flow!

The demonstration here is to pass around the special balls that glow and buzz when the metal contacts on them are connected by touching them.  Encourage the audience to make large circles and explore creating open, closed and short circuits.  (The most common “short” in the circuit is when the two people holding a ball are accidentally touching each other!)

## More about circuits...

- There is a special relationship between voltage, resistance and current!

- _[Simple Circuit Demo](file:///C:/Program%20Files/PhET/simulations/ohm1d/webstart.jnlp)_

**Notes:**
Use the “Simple Circuit Demo” link to open a Java demo that helps explore V=IR (without necessarily mentioning the equation itself).  You can explain that resistor is like a light bulb filament.  Describe that the moving blue dots are the electrons, and that their motion is the electric current.  The green dots in the resistor are the atoms that electrons can bump into.  Bumping into the resistor's atoms slows the electrons down, and heats up the resistor.

Ask the audience to help predict what will happen to the current and the temperature of the resistor as you change the voltage of the battery and the resistance of the resistor.  Finally, ask what will happen if you reverse the voltage!

## More about circuits...

- There is a special relationship between voltage, resistance and current!
- How fast do electrons and electricity really move?

- _[Simple Circuit Demo](file:///C:/Program%20Files/PhET/simulations/ohm1d/webstart.jnlp)_

- _[Electrons and Electric Signals](file:///C:/Program%20Files/PhET/simulations/signalcircuit/signalcircuit.jnlp)_

**Notes:**
The “Electrons and Electric Signals” link leads to another Java demo.  This demo has a switch and a light.  The electrons are shown as blue dots again.

First, choose the option to paint the first electron that leaves the switch.  Ask the audience when the light will turn on with respect to that electron.  When you close the switch, make sure you point out that the light turns on long before the electron travels all the way to the light!

Now also mark the signal.  Explain that electrons push on each other, and that the speed of them pushing on each other is the speed of light!

## Magnetism

- What is a magnet?
- How does it act?
- What kinds have you seen?
- What happens to non-magnets around magnets?

**Notes:**
Ask a few quick questions about what a magnet is and what they do.  It's possible you won't get much discussion on this topic, but someone will probably mention that they have poles, that opposite poles attract, like poles repel, and they stick to your refrigerator!

## Magnetism

- What is a magnet?
- How does it act?
- What kinds have you seen?
- What happens to non-magnets around magnets?
- We need another volunteer!
- What can you pick up with a magnet?
- Is it the same as we picked up with a static charge?
- Do magnets carry a charge?
- What will the magnetic force go through?

**Notes:**
In this demonstration, have an audience member try to pick up various objects with a magnet.  Notice that different items get picked up by magnets than got picked up by charged objects.  Not all materials show a response to a magnetic field.

You can also show that neither the magnets nor the items the magnets pick up are charged.

Finally, if strong magnets are used, you could even have someone put a magnet on the back of their hand and pick up paper clips on the palm of their hand.  With a strong enough magnet, you could even get a chain of paper clips!

## A Compass is a Magnet!

- Compasses align with magnetic field lines
- What does that imply?

**Notes:**
Discuss why compasses are useful (they point north!), then ask what that must mean...

## A Compass is a Magnet!

- Compasses align with magnetic field lines
- What does that imply?
- The Earth is a (really, really big) magnet!

**Notes:**
An interesting thing to point out here is that the magnet that is “buried in the Earth” is pointing the “wrong way!”

You could either demonstrate that this must be the case by putting a bar magnet next to a compass, or you can use the Java demo on the following side to show a bar magnet next to a compass...

## Electricity & Magnetism

- Special things happen when you have a changing magnetic field...

- _[Changing Magnetic Fields](file:///C:/Program%20Files/PhET/simulations/faraday/faraday.jnlp)_

**Notes:**
There are various tabs at the top of the “Changing Magnetic Fields” Java demo.

The demo starts on the “Bar Magnet” tab, which lets you show the field around a magnet, and how it interacts with a compass.  Put the compass at the end and to the side of the magnet, and flip the magnet's polarity.

Next, use the “Pickup Coil” tab to demonstrate that a changing magnetic field through a loop of wire generates electricity!  Try to have the audience notice that the electricity only works when the magnet is moving.  This is Faraday's law.

Finally, go to the “Generator” tab as a lead in to how power plants make electricity!

## Electricity & Magnetism

- Special things happen when you have a changing magnetic field...
- This is how power plants generate the electricity we use every day!
- Each type of plant uses something different to turn the magnets:
- Wind, water, or steam is usually used
- Coal, natural gas, and fission just make steam!

- _[Changing Magnetic Fields](file:///C:/Program%20Files/PhET/simulations/faraday/faraday.jnlp)_

**Notes:**
We're revisiting power plants.  This time, emphasize that each energy source used by a power plant is really just being used to turn magnets in a coil of wire in order to generate electricity.

Explain that many of the power sources, such as coal, gas and fission, are really just heating a large tank of water that produces steam.  Later, this steam turns a shaft that moves the magnets, then is condensed, recollected, and boiled again.

## Magnetism & Electricity ?

- We can also make magnets out of electricity!
- A loop of current creates a magnetic field
- More loops = more magnetic field!

**Notes:**
We've made electricity by moving magnets.  Now, explain that moving charges can also make a magnetic field.

The strength of the magnetic field depends on both the current through the wire and the number of loops of wire used.  More current and more loops means more field.

## Magnetism & Electricity ?

- We can also make magnets out of electricity!
- A loop of current creates a magnetic field
- More loops = more magnetic field!
- We need a volunteer!
- What can you pick up with an electromagnet?
- What does the electromagnet do to a compass?

**Notes:**
In this demonstration, ask an audience member to use the provided electromagnet (a 1.5 Volt batter plus a nail with wire wrapped around it) to pick up various materials and make a compass move.

You can also ask them to disconnect the battery after they've picked something up.  This will show that it is really the flowing electricity that's causing the magnetic field.

## Magnetism & Electricity ?

- We can also make magnets out of electricity!
- A loop of current creates a magnetic field
- More loops = more magnetic field!
- We need a volunteer!
- What can you pick up with an electromagnet?
- What does the electromagnet do to a compass?
- What other electromagnets have you seen?

**Notes:**
There are many examples of electromagnets that get used every day, however you won't always get a long list from your audience...

## Everyday Electromagnets

**Notes:**
Here are some fun examples of electromagnets:

Top left – A Magnetic Resonance Imaging (MRI) machine at a hospital

Lower left – A Magnetic Levitation (MagLev) Train

Top center – Speakers use electromagnets to reproduce sound

Lower center – A crane at a junkyard

Right – A Tevatron magnet

More examples include hard drives in computers, the read/write heads of VCRs, cassette tapes and credit cards, telephones, and more...

## Faraday and Lenz

- Faraday's Law tells us that a changing magnetic field induces a current
- This is what made power plants run!
- Lenz's Law tells us the consequences...

**Notes:**
Remind everyone that it was the English physicist Michael Faraday who discovered that changing magnetic fields induced an electric current which led us to modern power plants.

But Heinrich Lenz, a Russian physicist and world traveler, discovered some important details about the way that Faraday's law worked...

## Faraday and Lenz

- Faraday's Law tells us that a changing magnetic field induces a current
- This is what made power plants run!
- Lenz's Law tells us the consequences...
- We need another volunteer!

**Notes:**
This demonstration uses the long metal pipe (with a stand) to show that the currents induced by a magnet moving through a coil of wire end up resisting the passage of that magnet.

Have an audience member show that the magnet will not stick to the outside of the pipe.  Then, have them drop the magnet next to the pipe, showing that it falls normally.  Finally, have them drop the magnet through the pipe, and watch it as it falls.  Ask repeatedly if the magnet has gotten stuck anywhere or if it's being magnetically attracted to the pipe.

## Faraday and Lenz

- Faraday's Law tells us that a changing magnetic field induces a current
- This is what made power plants run!
- Lenz's Law tells us the consequences...
- We need another volunteer!
- The “induced electromagnet” creates a field that opposes the changing magnetic field!
- You don't get something for nothing!!

**Notes:**
Explain that this principle means that it takes a lot of effort to produce electricity!  This is why we have to rely on such powerful energy sources, like fission, to produce electricity at power plants.

## Particle Accelerators at Home!

- Did you know that you probably have a particle accelerator at home right now?

**Notes:**
The last few demonstrations have been saved until the end because they are some of the most visibly exciting.

First, ask if anyone knows what device in their home right now might be a particle accelerator.  (You might get some interesting responses!)

## Particle Accelerators at Home!

- Cathode Ray Tubes, the original kind of TVs, are particle accelerators!

**Notes:**
Explain that cathode ray tubes are really a particle accelerator.  Specifically, electrons are shot from the back of the tube to the front screen area.  

TVs have phosphorescent material on the front screen that glows when electrons pass through it.  Color TVs have three electron beams that shoot at three different colored phosphors (red, green and blue).

## Particle Accelerators at Home!

- Cathode Ray Tubes, the original kind of TVs, are particle accelerators!
- We need a volunteer!
- Magnets don't just effectother magnets, they alsobend moving charge
- Electromagnets in your TV make a singe electron beam draw a moving picture

**Notes:**
Previous experiments and demonstrations have shown that magnets will effect other magnets, and that moving magnets can even create electricity.  But so far, we haven't shown the major use of magnets at Fermilab, which is to control the motion of moving charged particles.

## Back to Charge...

- A Van de Graaff generator creates a large voltage difference
- We've learned a lot about static and moving charges today...
- Help us guess what will happen when we experiment with the Van de Graaff!

**Notes:**
The picture is of the Cockroft-Walton machine at Fermilab, which is the initial stage of the long chain of particle accelerators.  This machine acts a lot like a stack of Van de Graaff machines, each step up in the ladder increasing the voltage more and more.

You can do a lot of things with the Van de Graaff:- Make a stack of pie plate pop off of the top- Make styrofoam peanuts pop out of a pie plate that is taped to the top- Blown bubbles will attract toward, then fly away from the top, as they first get polarized, but then absorb a trickle charge and are repelled- Insulate yourself from the ground and make your hair stand up! (Start with machine off and hold top while standing on milk crate.  Then have someone else turn it on.  Keep holding the top until you've turned off the machine and discharged it!)

## Questions & Answers

- It has been a fun day!  Thank you for being such good hosts!!
- Any questions about charge, electricity or magnetism?

**Notes:**
So far, we haven't noticed any specific common questions that pop up frequently.

Lots of kids like to ask if you know someone they know at Fermilab!  As of 2006, there's about 2,000 employees, and hundreds of visitors and users at Fermilab.  That might help them feel better when you don't know their uncle who used to work there five years ago...

## Questions & Answers

- It has been a fun day!  Thank you for being such good hosts!!
- Any questions about charge, electricity or magnetism?
- Any questions about physics, science, scientists or Fermilab?

**Notes:**
So far, we haven't noticed any specific common questions that pop up frequently.

Lots of kids like to ask if you know someone they know at Fermilab!  As of 2006, there's about 2,000 employees, and hundreds of visitors and users at Fermilab.  That might help them feel better when you don't know their uncle who used to work there five years ago...

## Thank You!!!

- Please visit Fermilab anytime!
- The Lederman Center has lots of activities to help you learn about what we do at Fermilab
- We have buffalo and prairie trails, too!
- Useful links:
- Fermilab Education Office: http://www-ed.fnal.gov
- American Science & Surplus: http://www.sciplus.com/
- Java Demos: http://www.colorado.edu/physics/phet

**Notes:**
...And Thank You for helping give a “Charge! Electricity and Magnetism” demonstration!  Hopefully you've inspired some young minds to explore science!