Earth’s Magnetic Field

June 1, 2010

Marty Sagendorfby:  Martin Sagendorf

We recognize heat & cold, dry & damp, light & dark, and sound & silence.  However… I find it absolutely fascinating to consider that we also live within something that we can’t see, hear, touch, or taste.

We all Know:

Our planet has a giant magnet near its core and that its field extends over the whole of the Earth’s surface.  But, do we ever really think about this field that passes through soil, rocks, buildings… and us? Granted, relatively speaking this ‘field’ isn’t particularly strong.  In fact, it’s a rather weak field when compared to those of a horseshoe magnet or, particularly, a modern Rare Earth magnet.

A Great Demo to show Earth’s Magnetic Field:

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Leave a Comment » | Earth Science, Elementary level, experiments, High School level, magnetism, Middle School level, Physics | Tagged: , , , , | Permalink
Posted by Tami O'Connor

Eddy Current Tubes with Video

April 2, 2010

Ron Perkins, Educational Innovationsby: Ron Perkins

An eddy current is a current set up in a conductor in response to a changing magnetic field.  Lenz’s law predicts that the current moves in such a way as to create a magnetic field opposing the change; to do this in a conductor, electrons swirl in a plane perpendicular to the changing magnetic field.  Because the magnetic fields of the eddy currents oppose the magnetic field of the falling magnet; there is attraction between the two fields. Energy is converted into heat.

This principle is used in damping the oscillation of the lever arm of many mechanical balances. At the end of the arm a piece of flat aluminum is positioned to move through the magnetic field of a permanent magnet. The faster the arm oscillates, the greater the eddy currents and the greater the attraction to the permanent magnet. However, when the arm comes to rest, the attraction is negligible. Read the rest of this entry »

Leave a Comment » | College level, experiments, High School level, magnetism, Middle School level, Physics | Tagged: , , , , | Permalink
Posted by Tami O'Connor

The Revolution Top Floats – Why?

March 25, 2010

Marty Sagendorfby:  Martin Sagendorf

We often think we see forces.  However, in reality, we only see the results of forces.  To understand forces we must believe in Newton’s Third Law.  It states that all forces can only exist in opposite pairs and be equal in magnitude.  And… what is very interesting is that Newton’s Third Law does not stipulate that the forces be of the same kind.

Also, by Newton’s Second Law: If the (net) forces are equal, there will be no accelerations (Fnet = ma = 0)… in other words… equal and opposite (net) forces create a state of equilibrium.  An interesting example of equal and opposite (and unlike-type) forces is that exhibited by a combination of opposed magnetic fields within a gravitational (force) field.  These two different (types) of fields interact purely as ‘force fields’ – only their forces matter… not their types.

The Cosmic Magnetic Puzzle exemplifies a combination of such forces: a barbell containing two ‘donut’ magnets supported in mid-air above stationary pairs of magnets – with an additional pair of donut magnets maintaining the horizontal location of the barbell.

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Leave a Comment » | College level, experiments, High School level, magnetism, Middle School level, Physics | Tagged: , , , , , | Permalink
Posted by Tami O'Connor

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