11th of January 2019
The Faraday Effect & Eddy Currents
The principle that this demonstration showed was the Faraday effect, which describes the
process of changing a metal’s magnetic field by producing an electric current in the metal, creating a
repulsive and opposite effect to the initial magnetic field. For this principle, there were two demonstrations
shown during the in-class Spectacular that I attended: dropping magnetic balls through a tube and making
a piece of graphite float above a circular magnet.
During the experiment with the magnetic balls, two metal tubes were placed on the table – and
eventually would be lifted off the table in order to watch the motion of the magnets during the experiment
– with circular magnets fitted to fall through one end of each tube. Once Oren said the magnets could be
dropped into the tubes, they were released; instead of immediately falling through the tubes as expected,
they appeared to glide slowly through each tube until they exited from the other end. The motion of the
magnets demonstrates the Faraday effect since the speed of falling through the metal tubes differed from
that of dropping them in “normal conditions,” outside of the tube (downward motion due to gravity), for
example. As each magnet moved down the magnetic tubes, a repulsive magnetic force was generated,
pushing upward on the magnet as it fell until it came out of the opposite side.
The other experiment from this portion of the Spectacular was levitating a piece of graphite above
a magnet. In this demonstration, a piece of graphite is placed on top of a flat magnet that has a generator
attached to it. Once the generator is turned on, electric currents are run through the magnet, which then
cause the graphite to float above the magnetic surface. Similar to the previous experiment, creating a
repulsive magnetic force enables the graphite to levitate. In this case, the electric current induced
magnetic fields that flow in opposing directions, enabling the graphite to levitate above the magnetic
Currently, a common type of braking system in rollercoasters is the application of friction to halt
each train on a rollercoaster or to slow them down when approaching specific points on a track, be it hills
or turns, for example. Despite its success, a particular problem with this braking system is the generation 1
of heat will wear down the brakes over time, and, at higher speeds, it becomes increasingly difficult to
slow down the trains without providing too much pressure on the braking system. However, a remedy to
this system of braking exists: magnetism and the use of eddy currents.
Eddy currents form due to the Faraday effect creating a magnetic field once a charge is
introduced into the metal ; additionally, these currents form a magnetic field in an orientation opposite of 2
that which generated the currents, making a repulsive force. When applied to roller coasters, the currents...