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Forums
Physics
Classical Physics
Electromagnetism
How is the energy of a zero resistance circuit converted to rotational energy?
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[QUOTE="Henryk, post: 6156495, member: 568354"] A DC motor is consists of two parts: stator and rotor. Stator is a winding that creates a magnetic field in a certain direction. In small motors, it is replaced by a permanent magnet. Rotor is a series of coils offset at certain angles and connected to the commutator - a series of contacts arranged on a circle and connected to the stator and the coils and two brushes (usually graphite) that supply power to the that rotor coils. The brushes are arranged so that the magnetic field of the rotor is always perpendicular to that of the stator. Therefore, there is a torque acting on the rotor equal (in magnitude) to the stator field times the magnetization of the rotor. The torque converts the electrical energy to the mechanical one. The field of the rotor is proportional to the current supplied to its windings. Initially, when the rotor is starting, the current is the applied voltage divided by the coil resistance. However, as the rotor starts spinning, There is an induced EMF in the rotor coil opposing the applied voltage. The induced EMF is proportional to the angular velocity of the rotor. Therefore, the current through the rotor coil equals (voltage applied to the stator - induced EMF)/ coil resistance. One of the consequence of this is that every DC motor is a generator. It produces EMF proportional to it's rpm's. Second, when there is no load on the motor, it rotates with angular velocity that makes the induced EMF (almost) equal to the applied voltage. Now, going back to your original question. if the rotor resistance was zero, the current throught it would go to infinity at any rpms different that that which makes rotor windings' EMF equal to the applied voltage. In other word, that motor would turn and rpm independent of the applied load. [/QUOTE]
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Forums
Physics
Classical Physics
Electromagnetism
How is the energy of a zero resistance circuit converted to rotational energy?
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