What is the relationship between electrical power and torque in a generator?

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Discussion Overview

The discussion revolves around the relationship between electrical power and torque in a generator, particularly focusing on the effects of loading the generator and the implications of induced currents and magnetic fields. The scope includes conceptual understanding and technical explanations related to generator operation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that as a generator is loaded and requires more current, it must apply more torque to supply the power, questioning what resists the rotor from turning.
  • Another participant reiterates that the increased current demand is the answer to the torque requirement.
  • A participant raises a question about whether the mechanical power converted by the motor decreases when the current increases, citing the relationship between mechanical power, back emf, and current.
  • One participant proposes a hypothesis that the induced current creates an opposing magnetic field, which requires more torque from the prime mover to overcome this opposition.
  • Another participant seeks confirmation on whether the opposing magnetic fields created by the induced current and the original magnetic field resist each other, likening it to forcing two north poles of magnets together.
  • A later reply affirms the previous participant's hypothesis and suggests looking into Lenz's law for further understanding.

Areas of Agreement / Disagreement

Participants express varying degrees of understanding and agreement on the concepts discussed, but no consensus is reached on the implications of the induced currents and their effects on torque and power conversion.

Contextual Notes

Participants reference concepts such as back emf and Lenz's law, but the discussion does not resolve the complexities of these relationships or the assumptions underlying the claims made.

Who May Find This Useful

This discussion may be useful for individuals interested in electrical engineering, physics of generators, and the principles of electromagnetism, particularly those exploring the dynamics of torque and power in electrical machines.

Evil Bunny
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Lets say we have a fixed voltage output on a generator... As we load it down (require more current to flow out of it), the generator needs to apply more torque to supply the power.

Why? What is resisting the rotor from turning?
 
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in this case(the motor is loaded), will the mechanical power converted by the motor be smaller though the intensity of current has increased??

since P(mechanical)=E'*I where E' is the back emf, E' decreases when the motor is loaded?
 
Curl said:
there's the answer.

That's actually not an answer. It's a reading assignment...

Here's my guess. We induce a current onto a wire with a magnetic field. As current is flowing through that wire, it creates it's own magnetic field that is opposite in polarity to the magnetic field that is being induced onto it... These fields oppose each other which requires more torque from the prime mover to overcome it..?
 
bump... Is this correct?

Is the induced current creating a magnetic field that is opposite in polarity that makes it resist the current that was originally induced... Which makes them oppose each other, like the prime mover is now trying to overcome the opposing magnetic fields as if you were trying to force two north poles of magnets together?

Is this right?
 
Yes.

Do a search on Lenz's law and it basically says the same thing.
 

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