I would like to buy a strong magnet for lab use. I'm not sure how to
determine the strength of the magnet. Please suggest a website or/and
a product that's available online. Thank you.

Hello mar19-ga,

I?ve found several websites that sell magnets for science laboratories
and hobbyists. You didn?t specify exactly what type of magnet you?re
looking for but one of these sites should be sufficient for your
needs.

You also asked for information about determining the strength of a
magnet. I?ve included several sites that offer an explanation. In
addition, I?m also including a couple of lesson plans on this subject
that might be of interest to you.

Best wishes for your projects.

~ czh ~ 


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BUY LAB MAGNETS
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http://www.physics-net.com/d-magnets/sd220.htm
Science Lab Magnets

***** This site offers a variety of magnets for science labs as well
as for other uses. The sizes are indicated by shape and in inches.
Strength is indicated as ?strong? or ?powerful? or ?high.?

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http://www.indigo.com/magnets/magnets.html
Permanent Magnets
Magnets have a huge range of uses, in education, industry & at home.
Specific uses are far too numerous to list but from our standpoint, we
can simplify it by saying that some are specific to educational use
and the others have mixed use.

Weak Magnets: For Educational Use
Stronger Magnets: Industrial, Engineering & Research

----------------------

http://www.indigo.com/magnets/gphmgnts/metric-neodymium-rare-earth-magnets.html
Metric Neodymium Rare Earth Magnets
Neodymium rare earth magnets are the strongest magnets by weight and
have multiple uses in science, engineering, industry, magic and more.
All our magnets have a maximum operating temp. of 80C & a Curie temp.
of 310C; tolerance +/-0.05mm.

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http://www.engconcepts.net/Default.asp
Mr. George is delighted to bring you a wide range of neodymium iron
boron "Super Magnets" at great prices for inventors, hobbyists,
individuals, students, as well as businesses.

----------------------

http://www.engconcepts.net/Magnet_Ratings.htm
Explanation of magnet ratings



=================================
MEASURING THE STRENGTH OF MAGNETS
=================================

http://www.magnetsales.com/Design/FAQs_frames/FAQs_2.htm
How do you measure the strength or power of a magnet?

Most commonly, Gaussmeters, Magnetometers, or Pull-Testers are used to
measure the strength of a magnet. Gaussmeters measure the strength in
Gauss, Magnetometers measure in Gauss or arbitrary units (so its easy
to compare one magnet to another), and Pull-Testers can measure pull
in pounds, kilograms, or other force units. Special Gaussmeters can
cost several thousands of dollars. We stock several types of
Gaussmeters that cost between $400 and $1,500 each.

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http://spinalbrace.com/tectonic/strength.htm
Magnet Strength - What about Gauss

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http://www.lessonplanspage.com/ScienceMathMDMagnet-MeasureMagneticStrength12.htm
Title - Measurement of magnetic strength 
By - Scott Dan 
Subject - Science, Math 
Grade Level - 1st - 2nd 
Magnets: "Measurement of strength"

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http://www.sciencenetlinks.com/lessons.cfm?DocID=159
Magnets 2: How Strong is Your Magnet?

Purpose
To experimentally measure the strength of a magnet and graph how the
strength changes as the distance from the magnet increases, and as the
barrier (masking tape) is built between the magnet and an iron object.

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http://www.wondermagnets.com/cgi-bin/edatcat/WMSstore.pl?user_action=category&category=Magnets_and_Magnetism
MAGNETS and MAGNETISM

-------------------------------------------------


http://www.lbl.gov/Science-Articles/Archive/14-tesla-magnet.html
World Record Magnet 300,000 Times Strength of Earth?s Magnetic Field



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SEARCH STRATEGY
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strong magnet for lab use
magnet science laboratory
how to measure OR calibrate strength of magnet

The simplest qualitative way to measure the strength of a magnetic
material would be to see how much it can lift. You can easily rate
different magnets against each other in this fashion.

The most common magnets for lab use are neodymium, which are
relatively inexpensive and exceedingly powerful. A penny-sized
neodymium magnet can lift upwards of ten kilograms. Neodymium magnets
should be handled with care, however, as they are fragile and will
chip if allowed to snap together - potentially shooting bits of magnet
around the lab! They are also heat-sensitive, and will begin to anneal
around eight celsius, losing their potency, so store them with care.

If you need magnets that are more durable you can purchase samarium
magnets, which are resistant to heat and less likely to chip. They are
not as strong, magnetically speaking, as neodymium and somewhat more
expensive.

Finally, do not discount the option of electromagnets, if they will
suit your needs. A high-school textbook and household materials are
enough to build a simple electromagnet with the power to rival a piece
of neodymium.

Determining the strength of a magnet in quantitative terms is a very
complex equation, but if you have some common lab equipment at your
disposal not too difficult. Attach one piece of the magnet to a scale
or other apparatus capable of measuring force, and place an
equally-shaped piece of the same material near and facing it. While
the magnet is not a true monopole, if it is small enough there is not
enough error to completely throw this approximation off; the square of
the pole strength of the material will be approximately equal to the
force exerted multiplied by the square of the distance between the
magnet and the lump of iron. For a more precise calculation you will
need to take more elements into consideration, including the shape and
size of each magnet, and I would direct you to the Wikipedia article
'Magnet' if you require that. To put it simply, though, neodymium is
the 'best' lab magnet, samarium if you are working at high
temperatures, and the easiest way to compare magnet strengths is to
simply see how much similarly-sized and shaped pieces of magnet can
lift.

Take an old microwave apart and salvage the magnets from the magnetron.

Here's a good place to buy neodymium magnets:

http://www.kjmagnetics.com/

Neodymium are strong and available, but any question about the
strength of a magnet should be answered in part with a discussion or
reference to Gauss, which is the unit of measurement for magnetic
fields.

Type gauss meter in your google search.