Magnet Essay

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When a magnet is in motion near a non-magnetic conductor such as copper and aluminium eddy currents are induced in the conductor, causing a dissipative force called magnetic braking force, or a change in magnetic flux (figure 2). This force is dependent on: The size and shape of the conductor and magnet The strength of the magnet (μ) The conductors conductivity (σ_c) The distance between the conductive surface and the magnet (d) The velocity of the magnet (v)
According to Faraday’s law, discovered in 1831 by Michael Faraday, this alteration in flux produces electromotive force (EMF) and eddy currents inside the metal. (Meerman, 2014) This force is the retarding force that is associated with magnetic braking. According to Newton’s third
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There is a clear interaction between the magnet and the induced eddy currents, which leads to a damping force that consequently causes the magnet to fall in transient accelerated motion, which soon changes to uniform motion under the collective action of the gravitational and retarding forces. This constant speed is known as its terminal velocity. This experiment demonstrates the laws very well, however, it is not particularly useful for a comprehensive investigation as the magnet is out of view whilst in the tube. Lenz’s law can also be demonstrated through passing a metal sheet through a magnetic field and observing the slowing of the metal sheet, however, there are limited results from this experiment as the resources aren’t readily available. One of the benefits from this investigation is that the magnetic braking force acts continuously over the magnet, compared to a shorter period of time with a pendulum for example.

The rolling movement of the magnet down the aluminium channel creates a voltage of approximately 10 microvolts (Dynamo Principle). The electrical current created by this voltage differential causes a magnetic field in the aluminium. This magnetic field is out of phase with the magnet itself; moving against the magnet like a brake. For this reason the velocity of the magnet is significantly reduced. This phenomenon could be further increased if the channels were made of copper as they conduct electricity better than aluminium. (Keller,

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