Tag electromagnet

MacGyver Season 4 Episode 8 Science Notes: Father + Son + Father + Matriarch

rhettallain 2 Comments

Newton’s Third Law

It’s not a hack, but I wanted to go over this quote from MacGyver:

“Every action has an equal and opposite reaction.”

Clearly, he isn’t just talking about physics and stuff—so let me give a very brief explanation.

This originally comes from Issac Newton and his “three laws of motion”. What he (Newton) was trying to say was that forces come in pair—forces are an interaction between two objects. So, if object A pushes on object B with some force, then object B pushes on A with the same force but in the opposite direction. That’s what Newton meant to say—but it’s tough when no one has nailed down the operational definition of things like “force”.

However, the most common version of this “Law” uses the action and reaction term. Of course forces come in pair always—it doesn’t matter if the objects are moving or stationary. So, the “action” and “reaction” don’t always make sense. This is why I prefer the force law stated as the following:

Forces come in pairs. For every force, there is an equal and opposite force.

If you have to write it in that form—that’s the best way. But what about action and reaction? This statement is still true in many cases. Let me give you an example.

Take a balloon and fill it with air. Now let the air out and remove your hands from the balloon. What happens? The air inside the balloon is at a higher pressure than outside the balloon. This means the stretched balloon rubber PUSHES the air out. Oh, but forces come in pairs—this means that the air also pushes on the balloon. Since a force CHANGES the momentum of an object (where momentum is mass multiplied by velocity), the balloon speeds up one way (action) and the air speeds up the other way (reaction).

Yes, that is EXACTLY how a rocket works—except it uses a chemical reaction to push gas out instead of stretched rubber.

I spent too much time on this one quote. I can’t help myself.

Disabling a Contact Mine

These explosive bombs are magnetically attached to the vehicle. Obviously, you can’t just pull them off—that’s how they EXPLODE. So, MacGyver’s idea is to destroy their electronic components with the car’s battery. If he can run electrical current through the mine, then maybe they will be disabled.

Fortunately, the mine is on a metal hood—assuming the paint doesn’t form too thick of an insulating layer then he can use the car’s ground as one of the contact points. Then he would just need to run a wire from the positive terminal of the car’s battery (he could get the positive from the 12V outlet inside the car) to the mine.

Yes. This process might also kill the truck—especially if current goes through the ECU (basically the computer that runs the engine).

DIY Electromagnet

Electrical current creates a magnetic field. If you wrap a wire into a coil with multiple loops, each loop will create a magnetic field that adds to the other magnetic fields from coils. So, more loops means a great magnetic field.

If you put a ferromagnetic core in the loop (like iron or most forms of steel), then these electromagnetic loops will also magnetize the coil and make the whole thing even stronger.

This is exactly what MacGyver does. He uses his Swiss Army Knife as a ferromagnetic coil and a battery from a flashlight as the power source. Then he uses this to pull out a bullet fragment from a wound. Now, he has to get lucky to use this. Most bullets are made of non-ferromagnetic materials (like lead or copper). But if it has even a little bit of steel (or some other materials), there’s a chance he can pull it out with the magnet.

Oh, one last note. The wire can’t be plain copper wire. It has to have some type of electrical insulation on the outside. This insulation forces the current to move around in a loop instead of taking a short cut from the start to finish. Some wire has a rubber coating to insulate it—but in this case, it’s called “magnet wire”. It has a thin enamel coating so that you can wrap it into a coil.

Dobsonian Telescope

It’s not really a hack, but it is important for the plot. There’s a telescope that MacGyver is going to use later. It’s a Dobsonian mount.

The “Dobsonian” part really refers to the way the telescope is aimed and not so much about the optics. I’m pretty sure every Dobsonian telescope uses a Newtonian optic design. It uses a large focusing mirror at the base of the telescope. Here is a very basic design.

The nice thing about this design is that it’s actually quite simple to build. The only complicated part is the parabolic mirror (which you could also make yourself—but it would take some bit of time). Oh, I left off the walls of the telescope above because you don’t actually need them.

But what about the mount? The Dobsonian is basically just two swivel points. The base of the mount turns and then the telescope moves up and down. Super simple. But it’s not the best design for serious astronomy. The problem is that the Earth rotates. If you were to watch the stars in the sky over the course of a night, they would move in a slow circle about the Earth’s rotational axis. Sure, it’s takes 24 hours (about) for the stars to complete this circle—but they are indeed moving.

If you want to take a time exposure picture of a star (like for 10 minutes or so), then that star is going to move and leave a streak on the image. Actually, someone needs to remind me to take a “star trail” picture sometime. So, the Dobsonian mount has to move both rotation points in order to compensate for this star motion. It’s tough.

The other telescope mount design is called an equatorial mount. In this case, one of the rotation axes is aligned with the Earth’s rotation. That means that you can just slowly turn this one axis and a telescope will remain pointed at a particular star. This has nothing to do with MacGyver—but I just thought I would mention it.

Super Bright Moon

MacGyver needs a distraction. What about the telescope? So, here’s what he does: he aims the telescope at the moon and then lets the image project onto a baddie. The bright light is just the distraction he needs.

Here’s where a big telescope becomes useful. The diameter of the mirror (or lens if it’s a refracting telescope) is related to the light gathering power. All of the light that hits that large mirror is focused up to the eyepiece. So, even very dim lights can be detected. Yes, even very dark things like distant galaxies or comets (both of which can not always been seen by the naked eye) can be detected with a large telescope.

Actually, if you want to get into amateur astronomy you should start off with a nice pair of binoculars. They are much easier to set up than a telescope (because you just grab them out of the case and you are ready to go). Also, with large lenses they can really let you see some stuff that’s invisible to the naked eye. It’s not about the magnification, it’s about the light gathering.

Oh, but a full moon IS indeed super bright. You really can’t look at it with a large telescope unless you have some type of filter. Also, don’t look at the sun with a telescope. That is a super bad idea.

MacGyver Season 2 Episode 5 Science Notes: Skull + Electromagnet

rhettallain 3 Comments

Decoration with syringe hydraulics

As they decorate for Halloween, the crew builds this skeleton that is controlled by syringes. The basic idea is to use a tube to connect two syringes (the big kind). Fill it with water. When you push or pull on one syringe, it makes the opposite thing happen with the other syringe since water is incompressible.

Here is a nice video showing how to make something like this.

Directional Antenna

In order to track down a dude, MacGyver builds a directional radio antenna. Well, actually he just combines a yagi antenna and a dish antenna—I’m not sure it would work like that, but it looks cool.

I don’t think I should go into the physics of a yagi—it might take a while to explain. However, I can say this: that old style TV antenna you had on your roof? That’s a yagi. It does have a directional dependance on amplitude. That means that if you point it one way, you will get a better signal than pointing it another way.

DIY Thermal Camera

How do you find people in a dark abandoned military base? What about a thermal camera? A “thermal” camera is just like a normal camera except that it’s different. Instead of detecting electromagnetic waves in the visible region (we often call this visible light), a thermal camera works in the infrared range. That’s why they are also called infrared (IR) cameras.

Normally, that wouldn’t help you see in the dark—except for one important thing. All objects radiate light. The wavelength of this light depends on the temperature of the object. For most of the objects you see around you, the wavelength of radiated light is in the infrared range. So, with an IR camera these objects are like their own little light bulb. You don’t need an external light source—the objects are the light source.

Let me show you an example. This is an image using the FLIR One—it’s an IR camera attachment for your smart phone (pretty cool). Here you can see the family dog in IR. There’s a bunch of cool stuff you can see, but I will just leave this post for you if you want to know more.

The first devices to produce an IR image (mostly) came about in the 1950s. They used a single sensor that scanned over an area to produce an image. It wasn’t fast and the sensor had to be cooled. But still it worked.

So, how could MacGyver make an IR camera? Step one would be to find one of these sensors—maybe lead sulfide detector. This detector just gives a voltage though and not an image. To get an image, you need to scan over the scene and then run that into a television or something. Here is an early sketch.

Inline image 2

How far away could you detect a human? I tried this out using my kids and my FLIR One. Here’s what it looks like at a distance of 7 meters.

Inline image 4

Just for fun, here is the image from the episode.

In the end, IR camera’s are pretty complex. Honestly, it’s amazing that we have something that does this on a phone.

Escaping a hyperbaric chamber

Samantha Cage has been placed in a closed hyperbaric chamber that’s being filled with water. A hyperbaric chamber is essentially a person-sized scuba tank. You can put someone in there and then increase the pressure. This can be useful for a person suffering from decompression sickness (from scuba diving).

Anyway, she’s trapped and needs to escape. MacGyver builds a captive bolt gun to break the window. Oh, that’s cool and all—but I have a better option to escape.

What if you sealed up the chamber to get her out? It sounds crazy, but it would work. Here’s the problem. In order to add water to the chamber, you either need to increase the interior pressure by adding high pressure water. Or—you can add water while letting some of the air out. The second method is much easier to do (since it just uses normal water). But this means there is either a valve that is open to let the air out or maybe there are some old and bad seals that let air out.

Now, if you seal off the chamber the water can’t come in. And if the water does indeed enter, it will increase the interior pressure. Hopefully the pressure will get high enough on the inside that Cage can add a little extra and bust out.

It’s just an idea.

Electromagnet Lift

Could an electromagnet actually lift something large? Absolutely. Have you not seen those giant electromagnets at the junk yard that lift cars? But what about a human? The human body doesn’t really have enough ferromagnetic material in it for this to work (unless you are Magneto). However, it’s at least plausible if that person has a steel plate implanted. Yes. It’s true that many metal implants are titanium. Also, the steel implants are stainless steel and some versions of stainless steel aren’t magnetic. But still—it’s possible.

An electromagnet is really just a coil of wire with current running through it. It’s not hard to make, here you can do it yourself.

But what about a HUGE electromagnet? If you want a super strong magnetic field, you need a GIANT electric current. It’s possible to get perhaps 10 amps out of a truck engine (from the alternator or the battery)—but that might not be enough. My suggestion is to get a bunch of car batteries together so that you can get the highest current possible. Of course this high current is going to make the wires hot, so don’t run it for too long.

MacGyver Season 3 Episode 21 Science Notes: Treason + Heartbreak + Gum

rhettallain 1 Comment

Breaking Window Bars with a Bicycle

This is another classic MacGyver hack. There is a window with bars on the outside and Mac needs to get IN. Simple, just pull off the bars. Obviously you can’t do this with your hands, you need to build something.

I guess you would call this a hand-crank winch. That probably best describes what he builds. Actually, it’s a hand crank winch WITH a compound pulley. Here are a couple of pictures.

The main idea here is the same for ALL simple machines. It’s really about force, distance and work. Let’s start with a super basic definition of work (physics work).

W=Fd

In this expression (which isn’t technically correct—but that’s OK for now), W is the work, F is the force applied and d is the distance over which the force moves.

Now imagine I have a simple machine. I can put work into it and get work out of it. Assuming it is 100 percent efficient, the work in can’t be less than the work out (or you would get FREE ENERGY).

So, if you want to pull (or push) with a smaller force then you need to pull over a larger distance. For the output force, you need to have it move over a shorter distance to get a larger force.

With the winch, MacGyver turns a hand crank (part of the bike). If the garden hose (used for a rope) is wrapping around something with a smaller diameter, then for each rotation of the hand the rope will move a small distance. This is the key to a winch. Remember—smaller distance means larger force.

With the compound pulley, the same thing happens. By using multiple pulleys—you can make the pull force move over a larger distance thus increasing the output force.

Here is my initial diagram for how this might work.

Spark Gap Generator

You don’t get to see much detail here—so let me just explain the idea behind a spark gap generator.

First, I guess I should say what it is used for. Originally, a spark gap was a radio transmitter. It turns out that although it’s simple to build, you can only use one at a time because they don’t really use channels. In the case of MacGyver, he is using a spark gap to jam a phone signal (to prevent data transfer).

All of the wireless data works by broadcasting and receiving electromagnetic waves. Radio, microwave, visible light, x-rays…these are all electromagnetic waves (but with different wavelengths). Still, they are electromagnetic waves.

So, what about this spark gap? The idea is to create a repeating spark across some small gap. This spark is a very violent (electromagnetically speaking) event. It has accelerating electric charges which create EM waves. These EM waves are high enough intensity that they can make it such that other (more well behaved) devices can’t send or receive a signal.

But how do you make one of these spark gap generators? Really, you just need a battery and some wires. If you use the wires and battery you can create an electromagnet. That doesn’t make a spark, but if you can turn it on and off really quickly, then it will indeed make a spark. I built one using a moving metal switch. When the electromagnet is on, it pulls the metal and turns off the switch. Once the switch is off, the metal is no longer attracted to the electromagnet and it moves back in place to turn the electric current on again. This just repeats to make the spark.

Here is a video.

Here are some more details on this.

Oh, here is another way to make one of these spark gap generators.

Gum Wrapper Switch

The key to this episode (it’s in the title) is gum. MacGyver activates the spark gap by taking out a piece of gum. How would this work?

The purpose of a switch is to do something such that two wires are connected. In this case, the two ends of the circuit could be the foil wrappers for two pieces of gum. If you put an insulator (gum) in between them, then the circuit will be closed. Pull the gum out and then two foil pieces will touch and complete the circuit.

Here is a diagram I created for this.

MacGyver Season 2 Episode 3 Science Notes: Roulette Wheel + Wire

rhettallain 2 Comments

Is there a better MacGyver image than his radio build at the beginning of the episode? I think not. Here is an image.

Could you actually build a radio from a snow mobile? I think yes. Really, radios aren’t actually that complicated. The only difficult part would be building an amplifier so that the signal generated from a voice is powerful enough to be detected by someone’s radio. If the snow mobile had any kind of radio (like for listening), you would have all the parts you would need.

Stun gun on slot machine

They call these hand held zap things stun guns, but they don’t shoot. You just have to hold them up to someone to shock them.

MacGyver needs a distraction so he takes the stun gun and uses it on a slot machine. After that, the guy playing wins.

Is this even possible? Possible, yes. Likely, no. The stun gun has high voltage that creates sparks. These sparks can damage electronic equipment—especially the super tiny transistors in a computer chip. So, it’s possible that the stun gun does something to cause a win.

However, these slot machines are built with tampering in mind. They need to be able to resist humans messing around with them to win. So, I doubt this would work. Also, if MacGyver zaps that outside of the machine it’s probably grounded. This means that the electric current that gets into the case of the slot machine will just go around all the electrical components.

You probably have a better chance of winning on the slot machine than cheating on it.

Iris scanner hack

In order to get through an iris scanner on a door, Jack gets a close up picture of the target’s eye. Then Bozer prints out a fake lens to wear over the eye. Could this work? It’s possible.

In fact, check this out. Someone did the same thing with the Samsung Galaxy S8.

Handheld Cellphone Stingray

A cellphone stingray is a device that acts like a cell tower. Cell phones connect to it thinking that it’s just a tower—but blam, it’s actually another computer.

Of course the details are complicated (which means I don’t really understand them), but you would need some type of antenna. Jack has a tiny antenna in his cuff that has to get close enough to the target’s phone. I think this is plausible. At least it would give Riley a chance to get into the phone and steal some codes.

Magnetic Detector

Also known as a compass. MacGyver is trying to find a magnetic switch for a hidden door. He grabs a bit of metal (hopefully it’s ferromagnetic steel) along with a magnetic bottle opener.

The basic idea is that a metal like steel (most steel) has magnetic domains. When these domains are lined up, the material will act like a magnet. You can line up the domains by rubbing the steel with a magnet. Like this.

If the magnetized steel can float, it will rotate and point in the direction of an external magnetic field—either from the Earth or from that magnetic door switch.

OK, one small issue. In the episode it shows MacGyver rubbing the steel back and forth. You really just want to rub it one way. I think it would still work though. Oh, also many of those magnets like the one on the bottle opener have weird domains. They aren’t just like a plain north and south of a bar magnet, but it still might work.

Vacuum Cleaner Spider-Man

This is awesome (and mostly real).

Here’s how it works. The vacuum cleaner works by pulling air out of a region. If you put a vacuum cleaner over carpet, the air flow goes from the carpet to the vacuum cleaner (basically with just a super powerful fan). When the air moves in this manner, it often picks up other stuff—like dirt.

MacGyver has this vacuum hooked up to some metal tray covers. When the air is pulled from these covers, the air pressure inside the covers decreases. That means that the external pressure (due to the Earth’s atmosphere) will push the covers onto the glass wall.

Actually, this force from the atmospheric pressure can be quite large. The pressure is 10^5\text{ N/m}^2. So if the pressure inside the covers is just half an atmosphere with a radius of 10 cm, then the net force (for the two covers) would be:

F = PA=(0.5\text{ N/m}^2)(2)(\pi (.1\text{ m})^2) = 3141 \text{ N}

That’s some serious force. But wait! This is not the force that supports MacGyver. In fact, it is the frictional force between the cover and glass that keeps him from falling. The frictional force is an interaction between two surfaces that acts parallel to the surface. It depends on two things:

  • The types of materials interacting.
  • The magnitude of the force that pushes these two surfaces together.

If you push two surfaces together really hard, there will be a greater frictional force. So, this force from the vacuum cleaner exerts a force that increases the frictional force and this frictional force allows MacGyver to climb like Spider-Man.

Here is something similar with a guy that hangs from an overhang with a vacuum cleaner. Pretty cool.

Shrinking metal

This is real (based on something real). Yes, you can actually make metal things smaller. Here is a great video from Physics Girl (Dianna Cowern) that shows how this works.

The basic idea is to create a HUGE electric current very quickly. This large change in current can create a very high change in magnetic fields. When you put metal in this high changing magnetic field, it induces an electric current in the object. This induced current creates a magnetic field that interacts with the external magnetic field in such a way that the device gets squished. It’s awesome. Oh, when I say “a large change in magnetic field”, I am actually talking about the time derivative of the magnetic flux.

So, what do you need to make this coin shrink thing work? You just need super high current super fast. The best way to do this is to charge up some big capacitors and then discharge them through some wires. That’s essentially what MacGyver does.

The biggest problem is his capacitor. He builds one using two roulette wheels. Like this.

Yes. Any two metal devices can create a capacitor—but you want one with a large surface area and very close together. If you turned the two tables around so the flat side was close to the other one, it would be better—but it’s still a capacitor (but not really big enough for this job). Still, the idea is solid.