Can someone out there tell me why this model wont work.

Get a donut shaped perfectly circular magnet, with the north pole on
the inside of the hole, and the south pole on the outside of the donut.
Place a bar magnet on the exact center of the hole with an axle punched
through the south pole end, and the north pole end facing the north
pole side of the donut magnet. Cut a small triangular notch out of the
bar magnet's north pole end so one side of it is closer to the donut
magnet than the other.

Shouldn't this cause the bar magnet to rotate, depending on the side
that you cut the notch out of.

Supposing it does. What if you then hooked it up to an electric
generator which powers a coil of wires around the donut magnet, turning
it into an electromagnet with the same original properties. Wouldn't
this have a feedback type of effect, where the increased momentum from
the rotational force causing the generator to pump out a larger
current, which in turn increases the field strength of the
electromagnet?

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"Azor" wrote in message
ps.com...
Can someone out there tell me why this model wont work.

Get a donut shaped perfectly circular magnet, with the north pole on
the inside of the hole, and the south pole on the outside of the donut.
Place a bar magnet on the exact center of the hole with an axle punched
through the south pole end, and the north pole end facing the north
pole side of the donut magnet. Cut a small triangular notch out of the
bar magnet's north pole end so one side of it is closer to the donut
magnet than the other.

Shouldn't this cause the bar magnet to rotate, depending on the side
that you cut the notch out of.

Supposing it does. What if you then hooked it up to an electric
generator which powers a coil of wires around the donut magnet, turning
it into an electromagnet with the same original properties. Wouldn't
this have a feedback type of effect, where the increased momentum from
the rotational force causing the generator to pump out a larger
current, which in turn increases the field strength of the
electromagnet?
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The quickest answer is to refer you to the concept of "Conservation of
Energy". Basically it says "No Free Lunch". What you propose is a
perpetual motion machine that violates that. In practice, you won't even get
a self running toy.

In the setup that you describe, the magnetic field is the same at every
position of the rotor ( shift the rotor a bit and look at the geometry- it
doesn't change). However, the magnetic force depends on the rate of change
of field stored energy with position. This doesn't occur so no force is
produced.

There have been proposed perpetual motion magnetic machines in which the
force is position dependent but these also fail to produce net energy over a
revolution as in one revolution, the change in magnetic field energy will
be zero as you return to the original start point. That is - the energy
taken from the magnet has an average of 0 during a revolution. If net energy
were to be extracted from the magnet, it would quickly quickly cease to be a
magnet.

In conventional machines, with permanent magnet fields, no net energy is
taken from the magnets but the magnetic field acts as a kind of converter
allowing electrical energy to be converted to mechanical energy (or the
reverse) but there must be an external energy source.

Note also that a coil around the torus will not produce a field in the same
direction as the original field, so it won't "boost" the original field.
--

Don Kelly
remove the X to answer

In the setup that you describe, the magnetic field is the same at every
position of the rotor ( shift the rotor a bit and look at the geometry- it
doesn't change). However, the magnetic force depends on the rate of change
of field stored energy with position. This doesn't occur so no force is
produced.

There have been proposed perpetual motion magnetic machines in which the
force is position dependent but these also fail to produce net energy over a
revolution as in one revolution, the change in magnetic field energy will
be zero as you return to the original start point. That is - the energy
taken from the magnet has an average of 0 during a revolution. If net energy
were to be extracted from the magnet, it would quickly quickly cease to be a
magnet.

In conventional machines, with permanent magnet fields, no net energy is
taken from the magnets but the magnetic field acts as a kind of converter
allowing electrical energy to be converted to mechanical energy (or the
reverse) but there must be an external energy source.

Note also that a coil around the torus will not produce a field in the same
direction as the original field, so it won't "boost" the original field.
--

Don Kelly
remove the X to answer



Thanks Don, well explained.