Originally posted by menace71
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