7/25/2019 How to build an Electromagnet.docx

http://slidepdf.com/reader/full/how-to-build-an-electromagnetdocx 1/7

http://outpost1.stellimare.com/scouting/mb/electricity/electromagnet.html

Building an Electromagnet

This document is complete, but still considered a draft. Email Douglas Moyes with any questions you

have or comments. Last update: anuary !",!##$.

Things you'll need

• Magnetic %ire && special wire with very thin insulation

'description below(.

• )teel*+ron nail or bolt. + recommend a diameter *- '/mm(, !&

01'0&cm( bolt as smaller si2es may retain so much magnetism

they will not release paper clips once power is dropped ma3ing,

which isn4t too fun.

• 5raft 6nife*ra2or blade or sand paper 

•  7 battery power source&& 0 volt battery pac3 'two 77 in series(,

or volt lantern battery wor3s great. 8sing a wall transformer

will with your electromagnet will li3ely fry it9

Electromagnets wor3 on the principle that current flowing through a wire will produce a magnetic ield.

That magnetic field can then be transferred trough core made of ferrous material 'iron, or other materials

that interact well with magnetic fields(. They were used in early research with electricity.

;uilding an electromagnet is easy:

-. %rap a wire around an iron core 'a nail or a bolt wor3s great(

!. Ma3e sure your wraps are all going in the same direction. The

tighter the wraps, the closer they are together, and the more

you have, the stronger your electromagnet will be.

0. <ave a 0 volt power supply or volt lantern battery handy to

connect your electromagnet to 'you can use any power supply,

but read the note below(.

1

7/25/2019 How to build an Electromagnet.docx

http://slidepdf.com/reader/full/how-to-build-an-electromagnetdocx 2/7

=retty easy huh> %ell, people sometimes have trouble with this, and mainly it4s because they choose the

wrong wire, or they forget that they need to have both ends of their wire outside of the coil so they can

connect a power supply or battery to it.

The most common wire you4ll find has rubber for insulation this isn4t what you want to use. %ire used inelectromagnets use a single solid piece of wire coated in an enamel 'similar to paint( film for insulation.

Ta3e a loo3:

?ormal rubber insulated wire

Magnetic wire

 7s you can see, the rubber in the rubber insulated wire is about the same thic3ness as the radius of the

wire. ;ut in the magnetic wire, the insulation is so thin you can hardly see it when loo3ing at the wire

straight on. This means that more of the magnetic field is able to pass through our iron core ma3ing a

much stronger electromagnet. The magnetic force closer to the conductor is much stronger than that the

further out you go, so even being less than a millimeter closer to the conductor greatly increases the

magnetic field strength.

The drawbac3 to using magnetic wire is that the insulation can easily be removed by scraping it by

accident 'you4ll have to gently scrape the wire to remove the insulation on both ends so you can connect

a battery to your electromagnet(.

2

7/25/2019 How to build an Electromagnet.docx

http://slidepdf.com/reader/full/how-to-build-an-electromagnetdocx 3/7

@ou can get magnetic wire from many places, such as an old transformer, or from a electrical supplier.

)ome Aadio )hac3 stores still carry electrical components, so you can shop there. @ou can also try

www.7llElectronics.com, www.ameco.com, www.Mouser.com, or me B&(.

@our friendly Electricity Merit ;adge 5ounselor may even have some laying around '+ have a -0 pound !!gage magnetic wire, probably a few thousand feet worth(. Though, for your electromagnet -0 feet of wire

is more than enough&& we4re building electromagnets here, not rail guns....

If you're going to be using anything other than a battery, remember: @our electromagnet is Cust a

piece of wire, so you must add a resistor in series with your electromagnet or you could damage your

power supply. @ou will want at least !&-# amps going through your wire. Ma3e sure the resistor you use is

rated for your suspected power 'not doing this could cause the resistor to burn(:

Power=Voltage X Current

Current=Voltage/Resistance

  Or: Power=Voltage X (Resistance)2

)o, if we want - 7mp running through our volt power supply, we need a resistor rated for watts or

more, and it should have a resistance of hms 'or you could use -! $! hm -*! watt resistors wired in

parallel(. +f you try using a resistor that isn4t rated for the current you4re passing through it, it will burn up.

+f you4re using a volt battery or ! D cells '0 volts total if in series(, then you don4t need to worry too much

about those equations above right now. The wire can get hot when left connected to your power

source for too long. E!E" #$$% &$" E(E)T"$*+ET - &$" #$E#$(

E(E)T"I)+( $T(ET, $I $ 0I(( B" &$, )$( E(E)T"$)TE &$, + )+

)+E + I"E2

$3ay, let's build the electromagnet2

et all your materials together: %ire, bolt 'or a large nail or thic3 tent peg(, tape, something to scrape or

sand the thin insulation off with. @ou can also get a nut to add to the other end of the bold li3e + did at the

end, but you don4t need to.

@ou can clic3 on most of the images below to see a larger version.

tep 1 44 tart your Electromagnet

3

7/25/2019 How to build an Electromagnet.docx

http://slidepdf.com/reader/full/how-to-build-an-electromagnetdocx 4/7

)tart by winding the wire around your iron core. @ou should leave ! or more inches of wire out on each

end when finished. 7lways coil your wire in the same direction. +f you4re using a bolt, ta3e eFtra care to

avoid scraping the wire on the threads.

tep 5 44 0ind the wire around the iron core

8sing a bolt 8sing a nail

 7fter you have your bolt or nail partially threaded, put some tape on the threaded part to 3eep the wire

from moving around as you ma3e your coil. +f you4re using a threaded bolt, you can put your finger or

thumb on the bolt Cust over where you have threaded, and turn. @our thumb will guide the wire into the

groove. ;e careful not to scrape the wire on the threads9

+f you4re using a nail or large tent peg, you will need to push your coil closer together every now and then.

The nail that you see in the picture was actually too small. +t became magneti2ed on the first use, and the

paperclips wouldn4t drop after power was dropped.

6eep your threads as tight as possible, and always wind your wire in the same direction.

tep 6 44 +dd a second wrap 7optional8

)tart second wrap inished Magnet

This is an optional step. @ou can go bac3 over the windings you Cust made to create an even stronger

electromagnet. ;ut it isn4t really necessary. ust ma3e sure that you continue to wind your coil in the same

direction as before&& if you reverse it, your magnet will be made wea3er9

4

7/25/2019 How to build an Electromagnet.docx

http://slidepdf.com/reader/full/how-to-build-an-electromagnetdocx 5/7

@ou can see from the first picture that + have tape on the end that + stared on, and added a nut on the

other end. ;oth are optional. The tape is there to help 3eep the wire from unthreadding its self as you

wrap the wire.

@ou can lay down as many wraps as you want, but the first two will have the most effect.

irst, start off by ma3ing one big 1bac3 wrap1 with the wire moving around the core in the same direction

as you were ma3ing the small wraps. Then, ma3e a few small wraps at the top, and start ma3ing all the

wraps again, trying to 3eep the coil as tight and as close as possible.

+ also use that one last bac3 wrap to move the other end from the bottom bac3 to the top, ma3ing it easier

to connect a battery.

tep 9 44 "emoe the insulation

)anding 'safest method( )craping

3ay, now that you have finished winding, you need to cut the the eFcess wire off, leaving both ends ! or

more inches long.

?eFt, we need to remove the insulation at the ends so we can connect our battery. ?ow, on a normal wire

with rubber insulation, we Cust use a wire stripper, here, we can4t do that. %e either need to sand the

insulation off with sand paper, or gently scrape it off with a sharp 3nife.

%hen you are done, you should have about a half inch of eFposed wire on each of the two ends 'which

we4re going to call leads from now on(. The wire should loo3 li3e this:

5

7/25/2019 How to build an Electromagnet.docx

http://slidepdf.com/reader/full/how-to-build-an-electromagnetdocx 6/7

The red you see is the insulation, the copper color is the bare wire. +f your magnetic wire uses green

insulation rather than red, ma3ing it a lot easier to tell the bare wire apart from the insulation.

inal step, hoo3 it up2

+f your magnet didn4t wor3, or it was very wea3, then here are the li3ely reasons why: @our battery doesn4t

have a good electrical contact wit the two wire leads of your electromagnet, or you scraped some of the

insulation off wile winding, causing a short to the iron core 'you can use a multimeter to find out if that has

happened(. 7 bad electrical contact is easy to fiF, but if there is a short, you4ll have to start all over from

scratch with new wire 'or spray paint your bolt, then rewind(.

"ight #and "ule for )oils

This isn4t something you4re going to find in your merit badge boo3. ;ut did you 3now you can tell which

direction is north or south of your electromagnet by the direction of current and the way the coil is wound

in your electromagnet> @up, you can9 +t4s called the Aight <and Aule for 5oils 'there4s also one for motors

and generators(.

There is also a =D version for printing as a reference card.

<ere4s the online version:

6

7/25/2019 How to build an Electromagnet.docx

http://slidepdf.com/reader/full/how-to-build-an-electromagnetdocx 7/7

"ight #and "ule for )oils

=lace your right hand  over the coil, with

your fingers wrapped in the direction of 

current flow through the coil 'not electron

flow(. @our thumb will then point to the

magnetic north of your electromagnet

"emember:

@ou need to ta3e care to note the

direction the coil is wound. +f the coil is

wound in the opposite direction as shown

in the diagram, then your magnetic poles

would also be opposite as shown.

The parts to build this proCect can be obtained at your local hardware and electronics supply stores.

The other option is you can buy an Electricity Merit ;adge 6it from me that has all the stuff you need to

complete the electricity merit badge: batteries, battery holder, parts to build a )=DT switch 'and show that

it wor3s(, electromagnet wire, and a bolt.

 7ll images and teFt are subCect to copyright. =ermission is granted to use this material in the course of a merit badge class, or in a

public education setting. or all other uses, contact the author Douglas Moyes.

5opyright !## && %05 5ompliant.

<ome G )tellimare G )couting 

7