A serious Tesla coil, hand built:

Originally posted by menace71
My kid has a science project so I want to help him build a simple electromagnet I'm I can build it for under $20 .....I've seen some on youtube. I'm just wondering about the power source if I can get away with using some D cells? Iron bolt and copper windings should be easy


Manny

Take a look at this, a motor using a double A battery, a small magnet and a wire:

YouTube

Originally posted by menace71
Slick 🙂

You can certainly make an electromagnet powered by D cells, maybe 4 of them to give 6 volts. The key is having many windings of copper wire (insulated of course) around the iron core.

I played with electromagnets a few years ago for a demo at our kids grade school and I made what the kids called 'Electronic popcorn'. I wound a flat coil, like around 1/4 inch thick and a few inches in diameter, pancake shaped, with a hole the size of a toilet paper inner roll which is what I used for the center. In this case, I used 110 volt AC house current. So I put a small ball bearing, like about 1/4 inch diameter under the magnet in the toilet roll and hit the current. The dam thing shot up and stuck in the ceiling! The power of that thing was amazing! So I got out my trusty Variac, toned down the voltage to where I could get it to pop up in the air only a few inches.

Then I made an assembly out of a Dr Pepper can where I made this switch where the ball bearing completed the circuit to the little flaps of the soda can, about 1 inch by 1 inch and cleaned to be conductive and turned on the power, and now the ball bearing would shoot up the roll, fall back, hit the connector assembly, reactivate the magnet, it would shoot up again a few inches and continue likewise till I cut the power.

One thing I noticed was the little soda can switch assembly was getting a bit burned by the current so I modified the circuit to include a relay, where the coil of the relay was powered by the ball bearing and soda switch, and now the output of the relay did the heavy lifting. When that was finished, there was no more arc marks on the bearing or soda switch and I had substituted a transparent plastic sleeve for the toilet roll and the thing became a demonstration of both the magnet action and something I hadn't foreseen: the chaotic relation of the ball bearing movement, it was not like a metronome, which is what I expected. What happened was the bearing would fall back down but not take the same path each time and instead would approach the switch from some different angle or distance each time.

So it was unpredictable, as far as timing the jumps of the bearing. Pretty nifty thing for the students to see.

When I told the teachers about my idea for demonstrating science in action using household items (the pancake shape of the coil was provided by using two paper plates from the kitchen) and such.

So what they did was to take ALL the science class kids, about 5 separate classes and put them in one room to see the demo. There were over 100 kids in that demo.

I had worked up an electronic version of the old tin can tied by string communicator ( I had built one when I was 6, and knew they worked) but using wires and a special piezo pickup.

I also showed them how sound can travel through the floors from their desks to a sensor I built on the teachers desk, another piezo pickup on the end of a 12 inch ruler with a brick or something holding down one end of the ruler while the other end, sticking out almost a foot, held the sensor.

I worked up a way for the kids to see the output of the sensor using an oscilloscope and a double lens I rescued from an old projection TV, the lens was about 15 inches long and about 4 inches in diameter which was close to the diameter of my oscilloscope screen.

So I was able to throw the image of the oscilloscope onto a portable movie screen where the 4 inch line made by the scope was now about 4 FEET across.

So I hooked up the sensor directly to the Oscope, no amplifiers, and told a kid in the back of the class to hold his arm upright and then let it relax and hit his desk. So the energy of his arm hitting the desk went through the desk, through the floor and about 20 feet away to the teachers desk and my little ruler sensor assembly.

So they could clearly see the jump in the oscilloscope line when he dropped his arm on to his desk. They went 'wow' over that!

I then made some microphones from some styrofoam soda cups donated by a local Burger King and and glued some more piezo pickups to the bottom of the cup and did that in front of the class so they could see exactly what I was doing. I made 2 of those, and the first thing I did was to take one of the cups and had a volunteer put the cup against his chest through his clothes of course.

I hooked that sensor up to the scope, again with no amplification, and they could see the trace of his heartbeat on the giant oscilloscope display!

So I then hooked up the cup to a guitar amplifier I brought with me and showed them it was a microphone and had one of the kids talk into it and sure enough, his voice came clearly out the amp!

I also made one with one of my wife's sewing hoops, you know, the ones where there are two hoops, one inside the other so you can take cloth and make a tight drum for sewing.

So instead, I (of course in front of the kids) took saran wrap, put THAT in the hoops and made a tight drum and then glued a piezo sensor to the saran wrap and showed THAT was also a microphone.

One of the teachers said 'THAT'S a microphone'? And I proceeded to hook that to the guitar amp and sure enough, their voices came right through and amplified by the guitar amp.

They were really impressed with my demo of making science projects from household items and the kids all made up thank you cards, a really sweet thing I thought. I got over 100 cards from that one display and I meet kids now ten years later who remember that demo, they thought I was a genius🙂

Originally posted by menace71
Very cool I was able to duplicate the AA with copper armature and neodymium magnets to make a simple motor. My kid thinks it's very cool but I think the gauge of copper I bought is to thin and it's hard to make a balanced armature....I'm already $24 in and the wife does not want me to buy thicker copper LOL 🙂 But he needs to have something by Thursday

Manny

How could you have spent 24 bucks on that? That is saying you spent 22 bucks on the magnet.

As for that motor trick, I think it is about 99.99999% sure it is a trick. My guess is the table has some kind of vibrator underneath.

The thing is, there is no physical interaction between electric fields and magnetic fields, and the the problem with the electric field is, even if there was some connection, the fact that the 'magnet' is spinning would be sucking energy out of the battery. Since there is no connection to the battery it wouldn't matter much one way or the other, there would be no way to get energy from that battery in that manner.

For instance, if the effect was real, the poser could take away say, half the batteries and the rpm's should go down. Take all of them away and the spinning should stop.

Even if he did that, it would in all probability still be a hoax because he could just turn down the vibration of the gadget under the table. There is no image of the underside of the table so no attempt was made to give authenticity to this joke.

It is a joke. If you heard the guy, he said something about a 'huge' electric field. The electric field of a nine volt battery would at most be just that, the field produced by 9 volts of voltage differential. Then he puts in a bunch of AA batteries and the field there is that produced by a 1.6 volt difference, much less than the 9 volt one. So besides being a very low electric field, it is A, Static, no energy drain possible, and B, asymmetric in terms of the actual field that would exist in the center.

There is no way for the magnet to spin unless there was some kind of vibration coming under the table or just a spinner magnet underneath.

You can get those kind of magnets at science supply houses, where you have a heater plate with a spinning magnet under the plate and you can then take a magnet which is coated in teflon put inside the flask you want heated and stirred at the same time but you don't want to spend time just swishing it around with a stick or something.

We use that system at our lab here.

That is my best guess as to how he did this hoax.

Getting a thicker piece of wire shouldn't cost more than a buck for your little motor, BTW.

Originally posted by menace71
http://www.youtube.com/watch?v=KBZTXdf7c-o&list=PLEC48DB8D21DB0072


is this for real ? If so very cool

Manny

It's a fake.

For many reasons, including the fact that a magnate is not going to spin in a
static electric field, and those 9 volt batteries have both the positive and
negative terminals facing upwards and thus are going to disrupt the pathetically
tiny static electric field the other batteries would be making.

Originally posted by googlefudge
It's a fake.

For many reasons, including the fact that a magnate is not going to spin in a
static electric field, and those 9 volt batteries have both the positive and
negative terminals facing upwards and thus are going to disrupt the pathetically
tiny static electric field the other batteries would be making.

See my post.

Originally posted by menace71
See ......that's youtube garbage 🙂 I spent about $8 on 100ft of 20 ga copper wire bought to big bolts as originally I was going to try the electromagnet those were about 1.50 each and the 3 pack of magnets was about $8. there the neodymium type disc. The best one so far is D cell magnets and screw one strand of wire and that little bugger gets going fast !!

Manny

PS the wire gets hot 🙂

Yeah, it figures the wires get hot, it is conducting all the current the battery can supply, several amps for a short time. It's a short circuit, but the idea is there is a magnetic field around the wires that interact with the little magnet on the end.

Originally posted by menace71
See ......that's youtube garbage 🙂 I spent about $8 on 100ft of 20 ga copper wire bought to big bolts as originally I was going to try the electromagnet those were about 1.50 each and the 3 pack of magnets was about $8. there the neodymium type disc. The best one so far is D cell magnets and screw one strand of wire and that little bugger gets going fast !!

Manny

PS the wire gets hot 🙂

Batteries also have a short life. This other type of homopolar motor is easier to make. I too had trouble making a wire armature. The key to this is the screw has to be barely holding onto the magnet. I added some washers for weight. This video is poor but gives the basic idea.

YouTube

Originally posted by ChessPraxis
Batteries also have a short life. This other type of homopolar motor is easier to make. I too had trouble making a wire armature. The key to this is the screw has to be barely holding onto the magnet. I added some washers for weight. This video is poor but gives the basic idea.

http://www.youtube.com/watch?v=7SADAnt3hpA

That was the second one I did almost identical only my wire was copper the screw was flying just takes a bit of practice. I also made a simple electromagnet using to D cells it works great so my son is going to show them in his class tomorrow 🙂

Manny