Naked Science Forum
Non Life Sciences => Technology => Topic started by: Yahya on 02/04/2017 12:45:31
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electricity through the wire will cause electromagnetic force the force will pull the arm of the bell , suppose the moving arm moving very slowly as a result of benefiting from its kinetic energy, using its kinetic energy and reducing its speed of vibrating.
law of conservation of energy states that the kinetic energy of the bell arm should come from a source of energy, but how the kinetic energy is consumed from the electric source ?
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Each time the current flows through the electromagnet electrical work is done creating a magnetic field.
That field, in turn, does work by pulling on the armature.
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when closing the circuit , the current increases from zero to I , that induces the wire and causes work to be done and stored in the magnetic field, when opening the circuit if there is not this ferromagnetic material the magnetic field will disappear also that will induce the wire , and make eddy current and causes some heat energy in the core of the coil.
the stored magnetic field energy became heat due to Eddy current, so energy is conserved , but what if there is this bell arm, the energy coming from the drop or rise in current is kinetic energy and not Eddy current or heat, in other words it is the same whether the arm moves or at rest for the magnetic field , the magnetic field will behave the same at both cases, the magnetic field is not aware or does not react with the change in position of the arm , yet it actually differs as there is work done when it moves and work not done when it is at rest.
so what is the mechanism of energy consumption from the electric source to the moving arm ?
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Eddy current will affect the bell arm the same way in both cases , whether the arm moves or at rest specially if it moves very slowly.
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Ok , I understand now , it differs when there is change in position because there would be change in the magnetic field tension , but if it is at rest the won't be change in magnetic tension , the same way for a permanent magnet if I change the position of the iron close to a permanent magnet, by taking it away , I should exert energy , and the same energy can be extracted the opposite way. the energy will be consumed ( more work will be done ) due to change in position.
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Yes this is kinetic energy.