Hi.  

I'm making a device which requires a relatively small, but strong, electromagnet.

I've made a cylindrical electromagnet, with a diameter of 3cm and a
length of 10cm.  It has a metallic core.  I'm not sure what metal it
is exactly; all I know is it is ferromagnetic.  It is tightly wound; I
estimate about 5000 turns.  I've hooked it up to a series of four 6
Volt batteries.  With a gaussmeter I measured just over 1000 gauss at
the surface.

I require something more powerful.  I've tried adding more batteries
in series, and even in parallel, but to no avail.  I tried using car
battery and the wire heated up instantly and then began to melt; I
didn't even get a chance to see if the car battery worked, it being to
strong.

Searching the Internet, I've only been able to find one electromagnet
of similar proportions.  It has a max of 2000 gauss.  Still not
enough, I doubt.

---
Question #1

-> Are there any other electromagnets of similar size on the market,
which can create at least 5000 gauss, or anything near that?
---

---
Question #2

I've found the following site which describes the permeability of
various materials:

http://www.oz.net/~coilgun/theory/materials.htm

-> If I were to make an electromagnet using supermalloy as a core,
would I experience a significant increase in the amount of gauss
measured.
---

---
Question #3

-> If question #2 is correct, then where can I buy some supermalloy? 
And if supermalloy is too "rare" or too expensive, then what about the
other compounds on the list?

(The other compounds are are Mu metal, 4-79 Permalloy, 78 Permalloy,
Sinimax, Monimax, Hipernik, 45 Permalloy2, 45 Permalloy, 4%
Silicon-iron Grain-oriented, Purified iron, Iron, Cold rolled steel)

Anyway, I probally had used cold rolled steel for my electromagnet..
---

---
Question #4

I also require strong bar magnets, with the face as pole rather than the end.

-> Where can I get the *strongest* magnets, with a face (and pole) of
4cm by 4cm, and a height of 1cm?

Right now I am using two magnets side-by-side to make a face of 4cm by
4cm..  They only exert a field which is 800 gauss.
---

Thanks in advance.  :)

http://www.magnetechcorp.com/DC_Electromagnets.htm

If you are set on building your own magnet, this site may help.
http://education.jlab.org/qa/electromagnet_02.html

This is a good company - I have successfully used their products
before in research projects.
http://www.solenoidcity.com/

They give you all the information you need to calculate the
theoretical value for the amount of gauss ie wire gauge, ampere
windings, wattage ....

this one is the biggest they have
http://www.solenoidcity.com/electromagnet/e-40-300p1.htm

Hi.  I hope this reaches pwhitey86-ga.  You left a comment on this
question.  You  said:

"This is a good company - I have successfully used their products
before in research projects.
http://www.solenoidcity.com/

They give you all the information you need to calculate the
theoretical value for the amount of gauss ie wire gauge, ampere
windings, wattage ...."

I'm new to magnetism.  Could you please tell me the equation I can use
to figure out the theoretical value for the amount of gauss with the
variables given on the above website.

Thanks.

Go buy an inductor with something like 12 gauge wire.  Hook it up to a
car battery.  I'm not sure if it will give you 5000 G, but it'll be
awfully close.

What kind of a field do you need?  FYI, even the most powerful magnets
are not going to have a terribly high magnetic flux density (B) if
examined with the return path through air.  For example, typical high
strength neodymium-iron-boron magnets have a Br of 1.2 T (1T =
10,000G), but when measured sitting in air, you might only see .3-.4
T.  The only time you would see the 1.2 T is if you measured the B
while the magnet was effectively "keepered" by providing a return path
through a material with a high permeability.

In your electromagnet, putting more batteries in parallel does nothing
at all.  From the sound of it, the problem is that your wire can not
handle the current which would provide sufficient magnetic flux
density for your problem.  Simple answer is to use thicker wire.

There are many sources of Neo magnets around, and it is very common to
magnetize the through the face.  Search on Neodymium Magnet, or go to
ebay.

So here is how you calculate the theoretical value for the magnetic
flux density which has units gauss:

Variables:
B: magnetic flux (tesla)
mu_0: permeability constant (Newtons/Ampere^2)
N: number of windings (unitless)
L: length (meters)
I: current (Ampere)

B = mu_0 * (N / L) * I

The manufacturer gives "ampere windings" as a measure of the strength
of the magnet. Ampere windings are exactly what they say: Ampere *
number of windings

so now we have
mu_0 = 12.57E-7
N*I = 5740 Ampere windings (for the strongest electromagnet I showed you)
L = 4 inches * (.0254 meters/1 inch) = .1

Also: the units for B are in Teslas not gauss so we multiply by the
conversion factor 1E4 gauss / 1 Tesla

This gives

B = 12.57E-7*5740/.1*1E4
  = 710 gauss

so you can see this is not on the same order of magnitude as 5000
gauss that you asked for.

note that electromagnets on the order of 1E3 gauss are used for
industrial lifting machines and those on the order of 1E4 gauss are
used in MRIs

oops forgot one thing -- the relative permability of iron

so the equation is B = mu_Fe * mu_0 * (N / L) * I

where mu_Fe represents the relative permability of an iron core as
compared to an air core.
mu_Fe ~= 200
(I am pretty sure they are using an iron (Fe) core)
so there's another 2 orders of magnitude

That gives us 140000 gauss *theoretically*

-anyone sees this and disagrees - let me know

If you look at a relay, you will see that the total flux gap is only a
few millimeters. To get 5000 gauss you need to shorten your flux gap,
if I understand what you have tried before. The alternatve is to
emerse the coil in licqud helium which will carry away the heat
produced by perhaps 1000 amps of coil current. This will prevent the
wire from melting while your supply of helium lasts. For the long term
you need to capture the helium vapor as it boils off the coil and
reliquify the helium. Equipment to reliquify helium will cost several
thousand dollars.(If you can afford it look into Super conducting
magnets such as used for MRI = Magnetic Resonate Imaging) Liquid
nitrogen is much cheaper, but will give you less gauss without
damaging the wire.

Perhaps the 6 volt batteries that you connected in series delivered
less than one volt to your coil, instead of 18 volts. With 5000 turns
in a 3 cm coil 10cm long, the wire had to be fine, # 26? It should not
have over-heated with the car battery, so perhaps you had a short
circuit. What I'm saying is your report is not consistant with what
you think you did = an error occured in your experiment. ie if the
wire you wound on you magnet core was not insulated, you effectively
had much less than 5000 turns.  Neil

Thicker wire won't help much even if you can increase the diameter
well past 3 cm as the number of turn will decreases. Metal of the type
used in DC relays is about as good as you can get. I don't think any
super alloys are suitable for electro magnets.
 The 2000 gause magnet may require cooling for even one minute,
without a shortened flux path, but you may be able to push it well
past 2000 gause with liquid nitrogen cooling. At least you will know
the core is good metal for elctro magnets.   Neil