The size of a magnet is not relative to its strength. Many people believe that
the bigger the magnet the stronger it will be, this is not the case. Very high
strength magnets, for example, a 3,000 gauss/300 m tesla could be as small as
3mm in diameter. Similarly an 800 gauss/ 80 m tesla magnet could be quite large
(in therapeutic terms) and be the size of a 2 pence piece. The smaller of the 2
magnets is by far the stronger. The average size of a
medical magnet is
approximately 18mm in diameter. Healing magnets are small because they have to
be able to be placed as close to the point of injury as possible, if they wear
larger in size it would not be easy to attach the magnets over the pain point,
plus larger magnets are uncomfortable as they are heavy to wear and will “dig”
into the skin.
The size of the magnet does determine one important factor, the range of the
magnetic field. The larger the magnet the wider the spread of the magnetic
field. This means that the field will radiate outwards in a wide circle, however
it does not mean that the field will penetrate deep into the tissues. A small
magnet will not create such a wide spread magnetic field surrounding the magnet
but it will penetrate much deeper into the tissues.
The general rule to remember is:
1. A weak large magnet will cover a large area on the skin but will only have a
shallow penetration depth into the skin. 2. A strong small magnet will cover a small area on the skin but will have a
deep penetration depth into the skin.
To ensure that you have a wide magnetic field that also penetrates deep into the
tissues, choose a magnet that is over 2,000 gauss/260 m tesla and at least 8mm
in diameter.
The strength of magnet can be reduced by many materials. Plastic, glass and
thick clothing can inhibit the penetration of a magnetic field. When a magnetic
field covered by plastic, glass or thick materials the field first has to pass
through the covering substance, this has 2 effects:
1. It dramatically slows down the rate of absorption of the magnetic field. It
can take a magnetic field several hours to effectively penetrate through thick
plastic, or glass. 2. The magnetic field will start to dissipate as it moves through the solid
plastic, glass or thick material, this means when the field does reach the body
it will be much weaker than it was at the point of origin.
Ideally magnets should be placed directly onto the skin or over a very thin
layer of material, e.g. neoprene, nylon, cotton.
As you move away from a magnet the magnetic force decreases. What this means is
when you place a magnet on any point of the body, the magnetic field is at its
strongest right at the point of contact with the magnet and the body. The
farther the magnet is from an area the weaker the magnetic field. For example if
you placed a 3,000/300 m tesla magnet in the wrist the magnetic force around the
wrist would be 3,000 gauss/300 m tesla.
The strength of the magnetic field 4 cm away from the magnet surface will be
1/16th of the strength at the surface i.e. 187.5 gauss/18.75 m tesla, the
strength at 8 cm would be 1/64th of the strength at the surface i.e. 46.88
gauss/ 4.68 m tesla an so the equation continues the farther the distance from
the magnets surface. This principal is known as the inverse square law.
You do not have to memorise this law to be able to use magnets effectively but
it is very important to understand that the further away a magnet is to the
point of injury the weaker the magnetic field will be, which is why magnets
should always be worn directly over (or as close to as possible) the point of
injury.
