Unit 11 (Magnetism)

Special Science Teleclass: Magnetism

Saturday April 18, 2020

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I've included it here so you can participate and learn, too!

Discover how to detect magnetic fields, learn about the Earth's 8 magnetic poles, and uncover the mysterious link between electricity and magnetism that marks one of the biggest discoveries of all science…ever.

Materials:

Box of paperclips
Two magnets (make sure one of them ceramic because we're going to break it)
Compass
Hammer
Nail
Sandpaper or nail file
D cell battery
Rubber band
Magnet Wire

Optional Materials if you want to make the Magnetic Rocket Ball Launcher:Four ½” (12mm) neodymium magnets

Nine ½” (12 mm) ball bearings
Toilet paper tube or paper towel tube
Ruler with groove down the middle
Eight strong rubber bands
Scissors

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Special Science Teleclass: Magnetism

Monday October 20, 2014

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too!

Discover how to detect magnetic fields, learn about the Earth’s 8 magnetic poles, and uncover the mysterious link between electricity and magnetism that marks one of the biggest discoveries of all science…ever.

Materials:

Box of paperclips
Two magnets (make sure one of them ceramic because we’re going to break it)
Compass
Hammer
Nail
Sandpaper or nail file
D cell battery
Rubber band
Magnet Wire

Optional Materials if you want to make the Magnetic Rocket Ball Launcher:Four ½” (12mm) neodymium magnets

Nine ½” (12 mm) ball bearings
Toilet paper tube or paper towel tube
Ruler with groove down the middle
Eight strong rubber bands
Scissors

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Electromagnetic Crane

Sunday April 13, 2014

An electromagnet is a magnet you can turn on and off using electricity. By hooking up a coil of wire up to a battery, you will create an electromagnet. When you disconnect it, it turns back into a coil of wire. Since moving electrons cause a magnetic field, when connecting the two ends of your wire up to the battery, you caused the electrons in the wire to move through the wire in one direction. Since many electrons are moving in one direction, you get a magnetic field!
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Ferrofluid

Friday July 1, 2011

A ferrofluid becomes strongly magnetized when placed in a magnetic field. This liquid is made up of very tiny (10 nanometers or less) particles coated with anti-clumping surfactants and then mixed with water (or solvents). These particles don’t “settle out” but rather remain suspended in the fluid.

The particles themselves are made up of either magnetite, hematite or iron-type substance.

Ferrofluids don’t stay magnetized when you remove the magnetic field, which makes them “super-paramagnets” rather than ferromagnets. Ferrofluids also lose their magnetic properties at and above their Curie temperature points.

Ferrofluids are what scientists call “colloidal suspensions”, which means that the substance has properties of both solid metal and liquid water (or oil), and it can change phase easily between the two. (We as show you this in the video below.) Because ferrofluids can change phases when a magnetic field is applied, you’ll find ferrofluids used as seals, lubricants, and many other engineering-related uses.

Here’s a video on toner cartridges and how to make your own homemade ferrofluid. It’s a bit longer than our usual video, but we thought you’d enjoy the extra content.

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Electromagnets Exercises

Sunday April 4, 2010

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.

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Magnets Exercises

Sunday April 4, 2010

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Answers to Electromagnetism Exercises

Sunday April 4, 2010

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!

Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.

Answers:
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Answers to Magnets Exercises

Sunday April 4, 2010

Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.

Answers:
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Galvanometers

Sunday April 4, 2010

Galvanometers are coils of wire connected to a battery. When current flows through the wire, it creates a magnetic field. Since the wire is bundled up, it multiplies this electromagnetic effect to create a simple electromagnet that you can detect with your compass.
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Eddy Currents and Magnetic Brakes

Sunday April 4, 2010

Eddy currents defy gravity and let you float a magnet in midair. Think of eddy currents as brakes for magnets. Roller coasters use them to slow down fast-moving cars on tracks and in free-fall elevator-type rides.

Here’s what you need to do this activity:

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Which way is North?

Sunday April 4, 2010

I can still remember in 2nd grade science class wondering about this idea. And I still remember how baffled my teacher was when I asked her this question: “Doesn’t the north tip of a compass needle point to the south pole?” Think about this – if you hold up a magnet by a string, just like the needle of a compass, does the north end of the magnet line up with the north or south pole of the earth?

If you remember about magnets, you know that opposite attract. So the north tip of the compass will line up with the Earth’s SOUTH pole. So compasses are upside-down! Here’s an activity you can do right now…
Materials:

magnet
compass
string

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Electromagnet

Sunday April 4, 2010

After you’ve completed the galvanometer experiment, try this one!

You can wrap wire around an iron core (like a nail), which will intensify the effect and magnetize the nail enough for you to pick up paperclips when it’s hooked up. See how many you can lift!

You can wrap the wire around your nail using a drill or by hand. In the picture to the left, there are two things wrong: you need way more wire than they have wrapped around that nail, and it does not need to be neat and tidy. So grab your spool and wrap as much as you can – the more turns you have around the nail, the stronger the magnet.

(We included this picture because there are so many like this in text books, and it’s quite misleading! This image is supposed to represent the thing you’re going to build, not be an actual photo of the finished product.)

Find these materials:

Batteries in a battery holder with alligator clip wires
A nail that can be picked up by a magnet
At least 3 feet of insulated wire (magnet wire works best but others will work okay)
Paper Clips
Masking Tape
Compass

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How Generators Work

Sunday April 4, 2010

Have you noticed that stuff sticks to your motor? If you drag your motor through a pile of paperclips, a few will get stuck to the side. What’s going on?

Inside your motor are permanent magnets (red and blue things in the photo) and an electromagnet (the copper thing wrapped around the middle). Normally, you’d hook up a battery to the two tabs (terminals) at the back of the motor, and your shaft would spin.

However, if you spin the motor shaft with your fingers, you’ll generate electricity at the terminals. But how is that possible? That’s what this experiment is all about.

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Bouncing Magnets

Sunday April 4, 2010

Want to see a really neat way to get magnetic fields to interact with each other? While levitating objects is hard, bouncing them in invisible magnetic fields is easy. In this video, you’ll see how you can take two, three, or even four magnets and have them perform for you.

Are you ready?

Materials:

3 identical magnets

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Quick ‘n’ Easy DC Motor

Sunday April 4, 2010

Find a spare magnet – one you really don’t care about. Bring it up close to another magnet to find where the north and south poles are on the spare magnet. Did you find them? Mark the spots with a pen – put a N for north, and a S for south. Now break the spare magnet in half, separating the north from the south pole. (This might take a bit of muscle!) You should have one half be a north magnet, and the other a south. Or do you?

One of the big mysteries of the universe is why we can’t separate the north from the south end of a magnet. No matter how small you break that magnet down, you’ll still get one side that’s attracted to the north and the other that’s repelled. There’s just no way around this!

If you COULD separate the north from the south pole, you could point a magnet’s south pole toward your now-separated north pole, and it would always be repelled, no matter what orientation it rotated to. (Normally, as soon as the magnet is repelled, it twists around and lines up the opposite pole and snap! There go your fingers.) But if it were always repelled, you could chase it around the room or stick a pin through it so it would constantly move and rotate.

Well, what if we sneakily use electromagnetism? Note that you can use a metal screw, ball bearing, or other metal object that easily rotates. If your metal ball bearing is also magnetic, you can combine both the screw and the magnet together.

Famous scientist Michael Faraday built the first one of these while studying magnetic and electricity, and how they both fit together. What to see what he figured out?

Here’s what you do:

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Magnetic Fields

Sunday April 4, 2010

This is a quick and simple experiment to answer the question of magnetic field strength: Do four magnets have a stronger magnetic pull than one? You’ll find the answer quite surprising… which is: it depends. Here’s what you need to do to see for yourself:

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Relays & Homemade Shockers

Sunday April 4, 2010

This experiment is for advanced students. If you’ve attempted the relay and telegraph experiment, you already know it’s one of the hardest ones in this unit, as the gap needs to be *just right* in order for it to work. It’s a super-tricky experiment that can leave you frustrated and losing hope that you’ll ever get the hang of this magnetism thing.

Fear not, young scientist! Here’s a MUCH simpler relay experiment that will actually give a nice blue spark when fired up, along with a nice zap to the hand that touches it in just the right spot. You can also use this relay in your electricity experiments as a switch you can use to turn things on and off using electricity (instead of your fingers moving a switch), including how to make a latching burglar alarm circuit.

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Magnetic Sensors

Sunday April 4, 2010

Wouldn’t it be cool to have an alarm sound each time someone opened your door, lunch box, or secret drawer? It’s easy when you use a reed switch in your circuit! All you need to do it substitute this sensor for the trip wire and you’ll have a magnetic burglar alarm.

The first thing you need to do is get your reed switch out, because we have to tear into it in order to get the part we need. Here’s what you need:

Materials:

reed switch
magnet
LED
AA case
2 alligator wires
2 AA batteries

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Relays and Telegraphs

Sunday April 4, 2010

Relays are telegraphs, and they both are basically “electrical switches”. This means you can turn something on and off without touching it – you can use electricity to switch something else on or off!

We’re going to build our own relay that will attract a strip of metal to make our telegraph ‘click’ each time we energize the coil.

IMPORTANT! This experiment is very tricky to get working right. You’ll want to pair up with someone who’s handy in the workshop and has a keen eye and a feather touch for adjusting the clicker in the final step. Someone who is a patient, fix-it type of person will be able to help you get this project working well.

Note: There are bonus experiment ideas near the bottom once you’ve mastered this activity.

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Homemade DC Motor

Sunday April 4, 2010

Imagine you have two magnets. Glue one magnet on an imaginary record player (or a ‘lazy susan’ turntable) and hold the other magnet in your hand. What happens when you bring your hand close to the turntable magnet and bring the north sides together?

The magnet should repel and move, and since it’s on a turntable, it will circle out of the way. Now flip your hand over so you have the south facing the turntable. Notice how the turntable magnet is attracted to yours and rotates toward your hand. Just as it reaches your hand, flip it again to reveal the north side. Now the glued turntable magnet pushes away into another circle as you flip your magnet over again to attract it back to you. Imagine if you could time this well enough to get the turntable magnet to make a complete circle over and over again… that’s how a motor works!

This next activity mystifies even the most scientifically educated! Here’s what you need:

Materials:

magnet
magnet wire (26g works well)
D cell battery
two paper clips (try to find the ones shown in the video, or else bend your own with pliers)
sandpaper
fat rubber band

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Magnet Boats

Sunday April 4, 2010

We took our first step into the strange world of magnetism when we played with magnetizing a nail. We learned that magnets do what they do because of the behavior of electrons. When a bunch of those crazy little guys get going in the same direction they create a magnetic field. So what’s a magnetic field, you ask? That’s what this experiment is all about.

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Simple Magnet Experiments

Sunday April 4, 2010

Let’s play around with the idea of lining up all the mini-magnets inside an object to magnetize it. You’ll need a steel nail (steel is a combination of iron and carbon), a magnet (the stronger the better), and a few paper clips. Here’s what you do:

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Hearing Magnetism

Sunday April 4, 2010

Want to hear your magnets? We’re going to use electromagnetism to learn how you can listen to your physics lesson, and you’ll be surprised at how common this principle is in your everyday life. This project is for advanced students.

We’re going to invert the ideas used when we created our homemade speakers into a basic microphone. Although you won’t be able to record with this microphone, it will show you how the basics of a microphone and amplifier work, and how to turn sound waves back into electrical signals. You’ll be using the amplifier and your spare audio plug from the Laser Communicator for this project.

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Magnetic Grape

Sunday April 4, 2010

Every atom has electrons, and electrons both go around the core and also spin. Depending on how they spin and how much energy the atom has will determine what kind of magnetic properties your atom will have.

Iron is ferromagnetic, which means it’s attracted to both poles of a magnet – bring a nail close to any part of a magnet and you’ll always feel a pull, never a push.

Water (which is what your grape is mostly made up of) is diamagnetic. Things that are diamagnetic are repelled by both poles of a magnet, although very weakly (almost a million times weaker than ferromagnetic).

Paramagnetic materials (like a soda can, hydrogen, lithium, and liquid oxygen) is very weakly attracted to both magnetic poles, but it’s not noticeable until you bring the temperature of the soda can WAY down.

Here’s a nifty way to see diamagnetic properties in a material. Ready?

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Rail Accelerator

Sunday April 4, 2010

We’re going to build on the quick ‘n’ easy DC motor to make a tiny rail accelerator (any larger, and you’ll need a power plant and a firing range and a healthy dose of ethics.) So let’s stick to the physics of what’s going on in this super-cool electromagnetism project. This project is for advanced students.

Here’s what we’re going to do:

We’re going to create two magnetic fields at right angles (perpendicular) to each other. When this happens, it causes things to move, spin, rotate, and roll out of the way. We’re going to focus this down to making a tiny set of wheel zip down a track powered only by magnetism. Ready?

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Curie Heat Engine

Sunday April 4, 2010

marie-curie — Marie Curie, a scientist famous for being the first person to receive two Nobel Prizes as well as her extensive work on radioactivity.

Magnetic material loses its ability to stick to a magnet when heated to a certain temperature called the Curie temperature. The Curie temperature for nickel is 380^oF, iron is 1,420^oF, cobalt is 2,070^oF, and for ceramic ferrite magnets, it starts at 860^oF.

We’re going to heat a magnet so that it loses temporarily loses its magnetic poles, and watch what happens as it cycles through cooling. Pierre and Marie Curie’s first scientific works were actually in magnetism, not chemistry, and their papers in magnetic fields and temperature when among the first noticed by the scientists at the time.

Are you ready to see what they figured out?

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Linear Accelerator

Sunday April 4, 2010

There are two ways to create a magnetic field. First, you can wrap wire around a nail and attach the ends of the wire to a battery to make an electromagnet. When you connect the battery to the wires, current begins to flow, creating a magnetic field. However, the magnets that stick to your fridge are neither moving nor plugged into the electrical outlet – which leads to the second way to make a magnetic field: by rubbing a nail with a magnet to line up the electron spin. You can essential “choreograph” the way an electron spins around the atom to increase the magnetic field of the material. This project is for advanced students.

There are several different types of magnets. Permanent magnets are materials that stay magnetized, no matter what you do to it… even if you whack it on the floor (which you can do with a magnetized nail to demagnetize it). You can temporarily magnetize certain materials, such as iron, nickel, and cobalt. And an electromagnet is basically a magnet that you can switch on and off and reverse the north and south poles.

The strength of a magnetic field is measured in “Gauss”. The Earth’s magnetic field measures 0.5 Gauss. Typical refrigerator magnets are 50 Gauss. Neodymium magnets (like the ones we’re going to use in this project) measure at 2,000 Gauss. The largest magnetic fields have been found around distant magnetars (neutron stars with extremely powerful magnetic fields), measuring at 10,000,000,000,000,000 Gauss. (A neutron star is what’s left over from certain types of supernovae, and typically the size of Manhattan.)

Linear accelerators (also known as a linac) use different methods to move particles to very high speeds. One way is through induction, which is basically a pulsed electromagnet. We’re going to use a slow input speed and super-strong magnets and multiply the effect to generate a high-speed ball bearing to shoot across the floor.

For this experiment, you will need:
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Unit 11: Magnetism (Electromagnetism) Video

Sunday April 4, 2010

One of the four fundamental forces of nature, the electromagnetic force is the one that binds atoms together, allows you to walk down the street, and is solely responsible for bad hair days worldwide. One of the greatest leaps in science was the discovery that the electricity and magnetism were a part of each other, and not separate.

By the time you’re through with this lesson, you’ll have created particle accelerators, galvanometers, curie heat engines, unipolar motors, listened to a magnet (no kidding!), and build a working DC motor. Are you ready? This video will get you started on the right foot for your study into electromagnetism:

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Unit 11: Magnetism (Magnets) Video

Sunday April 4, 2010

Why do magnets stick together? And why does breaking one in half create a new set of poles? We’re going to explore these and other weird things about magnets. Are you ready? This video will get you started on the right foot for your study into with oddball world of magnets as you detected the earth’s magnetic pulse, discover magnetic levitation, uncover weird eddy currents that counteract gravity, and discover how a grape is magnetic. Let’s get started:

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