Electromagnet project

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hi i i'm doing a science fair project on how to make electromagnets stronger and i was wondering if you guys could answer some questions. first of all i need to find a good place to buy an iron core preferebly not online, i live in sandy utah in the united states. second i was wondering if you had any ideas on the design of the electromagnet other than a U and a normal rod. any other ideas would be apreciated.

p.s. please don't tell me how to calculate the strength of the magnet or the resistance of the magnet i already know thank you
 
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  • #2
berkeman
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hi i i'm doing a science fair project on how to make electromagnets stronger and i was wondering if you guys could answer some questions. first of all i need to find a good place to buy an iron core preferebly not online, i live in sandy utah in the united states. second i was wondering if you had any ideas on the design of the electromagnet other than a U and a normal rod. any other ideas would be apreciated.

p.s. please don't tell me how to calculate the strength of the magnet or the resistance of the magnet i already know thank you

Welcome to the PF!

Could you please tell us more about electromagnets? I'd like to learn the equations that you've been finding so far...
 
  • #3
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sorry you see berkeman i'm just a ninth grader that wanted to get some help on my project i am probably not the most reliable source of info to be asking questions to
 
  • #4
berkeman
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sorry you see berkeman i'm just a ninth grader that wanted to get some help on my project i am probably not the most reliable source of info to be asking questions to

Fair enough, but the reason I'm asking is to help you learn how to learn. What other research resources have you tapped so far to learn about electromagnets? Wikipedia? HowStuffWorks? HyperPhysics?

Our specialty here is to help students (of all levels) to understand what they have found in their research or classes -- not to give you the basics that you should be finding in other Internet resources. I know it sounds a bit weird, but the PF system works best if you do some work on your own (at the websites I mentioned already), and post specific questions here about things you may not understand about what you've read.

Learn how to learn... It's a good theme!
 
  • #5
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good point and yes i've been to wikipedia and howstuffworks even tho how stuff works was not as helpful as on most subjects and i've done a good deal of research but the only help google had was when it gave me links to here so thats why i thought i would start my own thread asking the specific questions i needed to know.

as to your earlier question about what i've learned so far i've know ohms law current= voltage/resistance but come to think of it that is the only actual equation i can remember

i thank you for advise about my learning but if you could help answer the questions i asked that would be extemely helpful thank you
 
  • #6
berkeman
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good point and yes i've been to wikipedia and howstuffworks even tho how stuff works was not as helpful as on most subjects and i've done a good deal of research but the only help google had was when it gave me links to here so thats why i thought i would start my own thread asking the specific questions i needed to know.

as to your earlier question about what i've learned so far i've know ohms law current= voltage/resistance but come to think of it that is the only actual equation i can remember

i thank you for advise about my learning but if you could help answer the questions i asked that would be extemely helpful thank you

So from your reading, what are the equations for magnetic field strength in the gap for a given Amp * Turns and Mu of the magnetic material? What is the effect of the air gap for an electromagnet? What physical geometries can minimize the gap?
 
  • #7
berkeman
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BTW, I applaud you for your interest in science in just 9th grade. Great stuff.
 
  • #8
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So from your reading, what are the equations for magnetic field strength in the gap for a given Amp * Turns and Mu of the magnetic material? What is the effect of the air gap for an electromagnet? What physical geometries can minimize the gap?

i've seen those equation but like i said only 9th grade i could'nt even begin to explain or even understand the equations

but please i joined this sight to get my questions answered and your kinda just asking me questions
 
  • #9
berkeman
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i've seen those equation but like i said only 9th grade i could'nt even begin to explain or even understand the equations

but please i joined this sight to get my questions answered and your kinda just asking me questions

Yes, we have a policy here on the PF of not giving out answers to schoolwork questions -- we try out best to help students learn how to learn, rather than just giving them answers. I understand it's hard just being in grade 9 so far, but I also applaud you and your interest in science so early in high school.

So let me try to post a couple more learning resources for you, to see if they can help you better than the wikipedia article.

http://science.howstuffworks.com/electromagnet.htm (HowStuffWorks intro article -- pretty basic)

http://en.allexperts.com/q/Electrical-Engineering-1356/Electromagnet-Design.htm [Broken] (Discussion of how to make the strongest electromagnet)

BTW, I got the second link by Googling electromagnet design tutorial. Often when you use Google, you can add the word tutorial on the end of your search terms, to get better results.

Finally, you will see in these articles and others, that by minimizing the gap, you can maximize the strength of the magnet. This is why U-shaped magnets are stronger than bar magnets. So depending on how you want the electromagnet to work, there are some geometries that give you the minimum gap (as long as the gap is big enough to allow grabbing whatever your target object is).

Can you think of how to make a cylindrical electromagnet that minimizes the gap? Like if you want to use it to pick up cars or other heavy stuff on the end of a crane....

http://1m1f.com/video/nvyL5s6hLjk/Electromagnetic-crane-car.html [Broken]

.
 
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  • #10
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thank you for your links they were helpful and i see what you mean that you don't just want to give me the answers.

i'm guessing your probably an expert in electrical engineering and have done a lot of projects like this so i was wondering do you know of any sources for me to get some cores for my electromagnets. google has been no help at all because any site that might sell what i need only sell in bulk or are on the other side of the world so any places to buy supplies in america (preferably utah) would be awsome.

and i was wondering how it would work if i just used a complete circle as an electromagnet core. would it make it stronger or cancel it out because there is no north or south pole. by the way for some reason i could'nt watch the crane video so if that video does answer one of these questions i'm clueless about it.

thank you for your help
 
  • #11
berkeman
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thank you for your links they were helpful and i see what you mean that you don't just want to give me the answers.

i'm guessing your probably an expert in electrical engineering and have done a lot of projects like this so i was wondering do you know of any sources for me to get some cores for my electromagnets. google has been no help at all because any site that might sell what i need only sell in bulk or are on the other side of the world so any places to buy supplies in america (preferably utah) would be awsome.

and i was wondering how it would work if i just used a complete circle as an electromagnet core. would it make it stronger or cancel it out because there is no north or south pole. by the way for some reason i could'nt watch the crane video so if that video does answer one of these questions i'm clueless about it.

thank you for your help

Sorry the link didn't work for you. I just now did a Google Videos search on crane electromagnet, and got a lot of hits. These should give you ideas:

http://www.google.com/search?q=crane+electromagnet&tbo=p&tbs=vid:1&source=vgc&hl=en&aq=f

And you wouldn't make a closed core into an electromagnet, because there needs to be a gap to let the flux out to pull in external ferromagnetic objects. If there is no gap, the flux stays all in the core.

As for stuff to make electromagnets out of -- how big do you want to make it? Golf ball size, soda can size, or bigger (yikes!)?

The easiest way would be to buy iron or steel pieces (I'm not sure which is best -- hopefully the links in my earlier post can provide that answer), and you need to choose the pieces to be able to make a shape that has the smallest gap you can make. I can think of how to make a good cylindrical one out of 3 pieces of metal that shouldn't be too hard to find. What were your thoughts on how to make the best cylindrical electromagnet?

What are you planning on using for your DC power source?
 
  • #12
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well as for what size of materiels i need at the moment i'm trying to figure out what material is best for the core i already have a steel rod 6 inches long 3/4 inch diameter and i wanted to try iron but google has just been sending me in goose chases on finding a place that would sell an iron rod but not in giant bulk.

and i wanted to know what do you think would be the easiest way to bend a metal rod because if i use the rod i already have to test the strength of the U shape then i don't have to go and buy another steel rod already shaped in a U

i already have a dc power source right now it's a 9.6 v 1800 mAH rechargable rc battery

and i had another idea i read about a E shaped electromagnet that had two positive charged ends and a negetive charged middle it has a larger distance between the poles but it seems like it might work better because it has three points of contact to what it is lifting what do you think

and thank you for the crane idea i did'nt think about trying to use that design in my experiment
 
  • #13
berkeman
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well as for what size of materiels i need at the moment i'm trying to figure out what material is best for the core i already have a steel rod 6 inches long 3/4 inch diameter and i wanted to try iron but google has just been sending me in goose chases on finding a place that would sell an iron rod but not in giant bulk.

and i wanted to know what do you think would be the easiest way to bend a metal rod because if i use the rod i already have to test the strength of the U shape then i don't have to go and buy another steel rod already shaped in a U

i already have a dc power source right now it's a 9.6 v 1800 mAH rechargable rc battery

and i had another idea i read about a E shaped electromagnet that had two positive charged ends and a negetive charged middle it has a larger distance between the poles but it seems like it might work better because it has three points of contact to what it is lifting what do you think

and thank you for the crane idea i did'nt think about trying to use that design in my experiment

You aren't thinking here! What can you do with that steel rod (no, don't bend it), to add another 2 pieces of steel, to make a closed magnetic path with a small planar opening? Watch the videos -- how have they wound the crane electromagnets? (It's not obvious from watching, but it's obvious from the tutorials...)
 
  • #14
berkeman
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Can you post an outline of your Science Fair Project Report so far? You should have at least an outline now. We can hopefully offer some suggestions for your outline...
 
  • #15
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well you wanted an outline of my project and here it is

so far i've been testing different variables and how much of a difference they make i have tested different gauges of magnet wire to use found out smaller the guage the stronger. then a electrical engineer friend of mine suggested covering an electromagnet with a pipe and block one side to strengthen the magnet and it was mostly inconclusisive because i'm pretty sure it strengthened the magnet but it killed my rechargable battary and pulled out 4.3 amps from a plug in power source that was only supposed to use 1.2 amps so that broke so i could'nt test his theory much and i'm not gonna try it again. today i'm going to test how much lengthining the electromagnet will help if any and tomorrow i am testing what material is best for an electromagnet core between aluninium iron and soft steel (would test more but not made of money). then lastly i'm testing how other designs will strengthen an electromagnet like the U and maybe a C if i can not find any other designs.

and you said i could add two more parts to my rod that i'm guessing would make a almost circle with a break in it for the magnetic poles. i would prefer not to because like i said not to much money (saving for a car so........) and i would have to buy the other parts for that electromagnet and i would need something to compare it to so i would need a stright bar the same size as the design you recommend to compare it to. thats why i would like to know how to bend the rod i have to save some money.

sorry i havn't had any time to look at the videos you recommended because i've had a lot to do so if i am way off with what design you are trying to point me to don't think me to ignorent i will look at the videos asap

thanks again for the help cya
 
  • #16
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i think i know exactly what you mean now i found this website that explains a ton in lamens terms if anyone else has questions about this type of thing refer them to this site please

http://sci-toys.com/scitoys/scitoys/magnets/calculating/calculating.html" [Broken]

so i think i know what you mean now that if i attach two pieces of metal to the ends of my rod then i will get the kind of C shape mentioned in the link. and that thats the best design because of it's low air gap between poles giving it a higher permebility letting me get more power with the same amount of current. please tell me i'm right and that i figured out the best design.
 
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  • #17
berkeman
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i think i know exactly what you mean now i found this website that explains a ton in lamens terms if anyone else has questions about this type of thing refer them to this site please

http://sci-toys.com/scitoys/scitoys/magnets/calculating/calculating.html" [Broken]

so i think i know what you mean now that if i attach two pieces of metal to the ends of my rod then i will get the kind of C shape mentioned in the link. and that thats the best design because of it's low air gap between poles giving it a higher permebility letting me get more power with the same amount of current. please tell me i'm right and that i figured out the best design.

Great! Good job.
 
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  • #18
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hey i just made a U shaped magnet for my expirement and just to see if it worked i tried wiring it all the way around the U instead of just the legs and it made an interesting electromagnet. it for some reason was pulsing like the electromagnet would turn on off on off on off in about a second why in the world would it do this????????
 
  • #19
berkeman
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hey i just made a U shaped magnet for my expirement and just to see if it worked i tried wiring it all the way around the U instead of just the legs and it made an interesting electromagnet. it for some reason was pulsing like the electromagnet would turn on off on off on off in about a second why in the world would it do this????????

What was the power source? It might have been going in and out of current limit, depending on what the current demand is of your coil.
 
  • #20
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i actually changed the power source to a power cord that i stripped at the end so i did not have to wait for the battery to keep recharging. the cords output is 12v 1833 mA
 
  • #21
berkeman
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i actually changed the power source to a power cord that i stripped at the end so i did not have to wait for the battery to keep recharging. the cords output is 12v 1833 mA

Have you looked at the output voltage with an oscilloscope? Is it steady? Or is it varying with the pulsations? If it's a switching supply and you are trying to draw more than the 1.8A out of it, it could be in "burp" mode current limit...
 

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