Measuring the strength (gauss/ tesla) of a magnet.
You may already have some therapeutic magnets that you are currently using or
want to use. The packaging that your magnet came in should state the gauss/
tesla rating of the magnetic device. If it did not state the rating on the
packet the manufacturer should have provided you with information regarding the
strength of the magnets.
If you have a magnet of unknown strength it is possible to find out the gauss/tesla
rating. You can do this by 2 methods:
1. By using a gauss meter. A gauss meter is an electronic device which measures
the magnetic field and the magnetic strength on the surface of a magnet. They
can measure magnets ranging from 200-20,000 gauss (20 m tesla- 2 tesla). A gauss
meter is also able to detect if a magnet is losing its strength (demagnetising).
A DC gauss meter (sometimes called a magnetometer)
Gauss meters are extremely useful in industry and for anyone who works with
magnets, but as they cost around £200. They are not an option for most domestic
homes.
2. If you do not have access to a gauss meter there is another way to
approximate the strength of a magnet. This method is based on Carl Freidrich
Gauss’s own original method for magnetic measurement and it is still used for
scientific experiments in most schools today.
For this method if calculation you will need a piece of paper, a pen (or pencil),
a compass, a ruler and a magnet that you know the strength of, plus of course
the magnet that you want to measure.
i. Place the ruler on the piece of paper.
ii. Place the compass on the piece of paper at the centre point of the ruler.
iii. Starting from one end of the ruler slowly move the magnet, whose gauss
rating is known, along the ruler towards the compass.
iv. When the needle of the compass begins to move toward the magnet, stop and
place a mark on the paper at the stopping point on the ruler.
v. Begin to move the unknown magnet towards the compass from the other end of
the ruler.
vi. When the compass again starts to move towards the unknown magnet stop and
place a mark on the paper at the stopping point on the ruler.
To work out the strength of the unknown magnet you must look at the 2 stopping
points marked on the paper. If the stopping point of the unknown magnet is
farther away from the centre of the ruler then the unknown magnet is stronger
than the known magnet and if the stopping point of the unknown magnet is nearer
to the centre point of the ruler then the unknown magnet is weaker than the
known magnet. This is a very approximate calculation of the strength of the
unknown magnet, calculate the exact strength you will need to work out the ratio
of the square distances between the 2 magnets and the centre point of the ruler.
If you are unable to use any of these 2 methods then I would suggest you contact
the supplier and ask for the strength of the magnet, if they can not or will not
tell you the strength , then do not use the magnet.
