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Diary of making an electromagnet

 


KHO
Ok, so I have begun making my first electromagnet today. After I have made a few basic electromagnets and understand the principles behind them, I will embark on another project, a pendulum that is allowed perpetual motion thanks to these magnets.

For my first step I attempted to wrap some thin enameled wire (that I thought was copper) around several objects that I believed to be iron. I did this because an iron object with round copper wire around it produces an electromagnet once current is run through it. Its a pretty basic concept, so I started off with some nails I found lying around the house and some wire I found lying in a box. Looked copper to me!

For about a half hour I ran wire around several test nails, each varying in density of coil and size of nail and length of wire. Each one returned no results. I tested the functionality of the 9V battery I was using by running some aluminum wire across the top of both connectors on it and touching it, the current was working fine.

At this point I realized the wire I'm using clearly isn't conducting the current as I tried performing this same test (running wire cross the + and - side of the battery) and no current flowed though. The local electronics store is closed at this hour, so I will stop this journal here and continue tomorrow after I pick up some copper wire =D.
Indi
KHO wrote:
Ok, so I have begun making my first electromagnet today. After I have made a few basic electromagnets and understand the principles behind them, I will embark on another project, a pendulum that is allowed perpetual motion thanks to these magnets.

i hope you're using "perpetual" in a metaphorical sense. If not... good luck. ^_^;

KHO wrote:
I tested the functionality of the 9V battery I was using by running some aluminum wire across the top of both connectors on it and touching it, the current was working fine.

You probably ruined the battery when you did that, eh? In fact, you'd probably already ruined the battery when you first connected it to the wire wrapped around the nail. Think about the circuit you just built. You have a battery connected to a wire... and pretty much nothing else. And the coil resistance is probably negligible... seriously you'd have to handwrap for a week before the resistance and inductance of that coil is appreciable. ^_^; So basically, you just short-circuited the battery.

Got any resistors? A small one will do. Bigger is safer, but don't go too big. Let's say a safe current is 1 mA... just enough to feel. Do you know the equation to find the needed resistance given the current of 1 mA and a voltage of 9 V? (You really should plan a bit before diving in. It is possible to kill yourself with a 9 V battery. Yes, it really is.) A resistor in series with your electromagnet coil with limit the current to safe levels, protecting both you, and the battery from being drained too quickly. Then, assuming your nail is iron, you'll get your electromagnet. (Of course, if you have a long enough wire, you won't need a resistor... but how long is long enough? Break out your calculator and work it out.)

Buuuuut. ^_^; - and i'll keep saying this - you really should crunch the numbers before you invest too much time and money in this. How powerful do you want your electromagnet to be? 1 tesla? That's about a weak permanent magnet, i think. How many turns at what current do you need to get that? Look up the equation and find out. Is the wire you're using capable of that current?

KHO wrote:
At this point I realized the wire I'm using clearly isn't conducting the current as I tried performing this same test (running wire cross the + and - side of the battery) and no current flowed though. The local electronics store is closed at this hour, so I will stop this journal here and continue tomorrow after I pick up some copper wire =D.

i'd bet you already do have copper wire, and it is conducting current just fine... fine enough in fact that it burned out your 9 V in a blink. i'd bet also that your electromagnet was working... but it was just far too weak for you to detect.

You're working blind, so you have no clue what's going on. That's both inefficient and dangerous. Sit down, plan it out. Crunch the numbers, and you will see what's going wrong, rather than wasting time and money on shot-in-the-dark guesses.
Chris65536
Quote:
pendulum that is allowed perpetual motion thanks to these magnets


On this forum, we obey the laws of thermodynamics! Very Happy


Numbers are your friends. Except 7. He's a right sod when he gets drunk.

But seriously: plan twice, build once. As an example of the wrong way to do things, in physics class we had to build a loudspeaker (which is an electromagnet wrapped around a permenant magnet attached to a cone of paper). By not reading the instructions (or thinking about what I was doing), I selotaped the electromagnet to the permenant magnet. No movement = no sound.

A good item to invest in for electical testing is a multimeter. This allows you to test electrical resistance, current and voltage without shorting out your batteries.
ocalhoun
KHO wrote:
Ok, so I have begun making my first electromagnet today. After I have made a few basic electromagnets and understand the principles behind them, I will embark on another project, a pendulum that is allowed perpetual motion thanks to these magnets.

For my first step I attempted to wrap some thin enameled wire (that I thought was copper) around several objects that I believed to be iron. I did this because an iron object with round copper wire around it produces an electromagnet once current is run through it. Its a pretty basic concept, so I started off with some nails I found lying around the house and some wire I found lying in a box. Looked copper to me!

For about a half hour I ran wire around several test nails, each varying in density of coil and size of nail and length of wire. Each one returned no results. I tested the functionality of the 9V battery I was using by running some aluminum wire across the top of both connectors on it and touching it, the current was working fine.

At this point I realized the wire I'm using clearly isn't conducting the current as I tried performing this same test (running wire cross the + and - side of the battery) and no current flowed though. The local electronics store is closed at this hour, so I will stop this journal here and continue tomorrow after I pick up some copper wire =D.

Perpetual only in a sense; you'll have to supply the electromagnet with oscillating current for as long as you want the pendulum to swing.
It isn't really that important that the wire be round; it can be coiled in around a square, triangle, whatever you want, so long as it is coiled, and coiled in the same direction the entire way.
The exact composition of the wire doesn't matter at all, as long as it is carrying current. You could use a wire made of anything conductive.
Also, it isn't absolutely essential that you have an iron core for your magnet. Even a coil with nothing in the middle will produce a magnetic field, but adding iron in the middle of it does greatly improve the strength of the field.

My suspicions about why your experiment is failing so far:
*The wire you are using is broken at some point, preventing the flow of current.
*The connections to the battery are not secure, preventing current flow
*At some point the insulation of the wire is insufficient (you are using insulated wire, right?), and the current is being shorted through the nail, rather than coiling around it.
*It did work for a very short time before the extremely low resistance of just a short wire drained the battery.
*It did work, but the magnetic field was so weak that you didn't notice the deflection of the pendulum. You need to either pulse in on and off at twice the natural frequency of the pendulum, or reverse the polarity at the natural frequency of the pendulum (which will depend on the length of the pendulum). This will make it swing back and forth, adding more momentum to each swing.


(It just occurred to me how you might be intending to make a perpetual motion machine with magnets and a pendulum... Are you thinking that a magnet on a string will reverse around at the apex of each pendulum swing, and then be attracted towards the center, and as it passes over the center be repelled until it swings up and turns around again? First of all, it would point the attracted side of the magnet straight down when directly over the center, and end up stationary pointed straight down towards the fixed magnet. Even if this could be prevented, the friction of the air and bending rope would eventually stop the motion.)
ptolomeo
What do you have against the perpetual pendulum? wouldn't it be nice?
ocalhoun
ptolomeo wrote:
What do you have against the perpetual pendulum? wouldn't it be nice?

It would be very nice. In fact, you would astound the entire scientific community with it, because for a long time they've thought that it was impossible. (With very good reason!)
Bikerman
ptolomeo wrote:
What do you have against the perpetual pendulum? wouldn't it be nice?

Specifically? The first and second laws of thermodynamics and the conservation of energy/mass. Would it be nice? Not sure about that since it would require our physical laws to be completely rewritten. Exactly what the consequences would be I can't say off-hand but I tend to think that the universe works OK as it is, so best not to mess it up...
Afaceinthematrix
Bikerman wrote:
ptolomeo wrote:
What do you have against the perpetual pendulum? wouldn't it be nice?

Specifically? The first and second laws of thermodynamics and the conservation of energy/mass. Would it be nice? Not sure about that since it would require our physical laws to be completely rewritten. Exactly what the consequences would be I can't say off-hand but I tend to think that the universe works OK as it is, so best not to mess it up...


It would solve some energy problems, though. So I'd argue that it may be nice, although highly inconvenient for the scientific community.
Bikerman
Suppose the 2nd law of thermodynamics was wrong. You pour a cup of hot coffee and wait for it to cool. It doesn't cool. Then, suddenly the coffee turns back into beans.....
That would make my life unbearable Smile
ocalhoun
Bikerman wrote:
Suppose the 2nd law of thermodynamics was wrong. You pour a cup of hot coffee and wait for it to cool. It doesn't cool. Then, suddenly the coffee turns back into beans.....
That would make my life unbearable Smile

It won't suddenly make every effect of the 2nd law reverse, of course, but it is remotely possible that someone could find an exception to the 2nd law, much like how relativity theory finds exceptions to newton's laws.
Bikerman
ocalhoun wrote:
Bikerman wrote:
Suppose the 2nd law of thermodynamics was wrong. You pour a cup of hot coffee and wait for it to cool. It doesn't cool. Then, suddenly the coffee turns back into beans.....
That would make my life unbearable Smile

It won't suddenly make every effect of the 2nd law reverse, of course, but it is remotely possible that someone could find an exception to the 2nd law, much like how relativity theory finds exceptions to newton's laws.

Well, sort of - Relativity isn't really an exception to Newton - it's more of a 'grand picture' whereas Newton is a 'local view of the same picture'.
ocalhoun
Bikerman wrote:
ocalhoun wrote:
Bikerman wrote:
Suppose the 2nd law of thermodynamics was wrong. You pour a cup of hot coffee and wait for it to cool. It doesn't cool. Then, suddenly the coffee turns back into beans.....
That would make my life unbearable Smile

It won't suddenly make every effect of the 2nd law reverse, of course, but it is remotely possible that someone could find an exception to the 2nd law, much like how relativity theory finds exceptions to newton's laws.

Well, sort of - Relativity isn't really an exception to Newton - it's more of a 'grand picture' whereas Newton is a 'local view of the same picture'.

Well, there you have it, perhaps someone will find a 'grand picture' that makes us realize that the laws of thermodynamics take a limited view on the world.
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