Theoretical question about an electromagnet in an AC circuit

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Discussion Overview

The discussion revolves around the theoretical application of an inductor in the neutral line of an AC circuit to create an electromagnet using the current that has already been utilized by a heating element. Participants explore the feasibility of generating magnetic fields from what is perceived as "waste current" and the implications of energy conservation in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether an inductor could be used on the neutral line to create an electromagnet without affecting the overall voltage or amperage, suggesting the possibility of using "waste current" for additional purposes.
  • Another participant argues that there is no such thing as waste current, stating that adding an inductor would reduce the voltage available to the heating element, thus negating any perceived benefit.
  • A third participant explains that a current flowing through an inductor generates a magnetic field, but this process involves energy loss, which must come from the circuit, emphasizing the principle of conservation of energy.
  • Some participants suggest that if the mains supply were DC, it might be possible to create a magnet without additional energy costs, but they acknowledge that energy must initially be supplied to establish the magnetic field.
  • There is a discussion about the implications of zero resistance in conductors and how it relates to energy storage and losses in magnetic circuits, with references to induced eddy currents and heat loss.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of using an inductor in the neutral line for creating an electromagnet. While some explore the theoretical possibilities, others firmly argue against the idea, leading to an unresolved discussion with multiple competing perspectives.

Contextual Notes

Participants highlight the importance of energy conservation and the implications of circuit parameters when discussing the use of inductors. There are unresolved assumptions regarding the nature of current flow and the effects of resistance in the circuit.

Wattif
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TL;DR
Can an inductor used as an electromagnet be in an AC circuit without
affecting the overall circuit
This may be a stupid question, but here is what I am asking.

Using a very simple circuit, say 120v AC water heating element rated at 1000 watts
meaning 120v AC hot leg on 1 terminal and a neutral on the other terminal.
That would give 8.3 amps of current, meaning the resistance would be 14.4 ohms.

Now after the resister the neutral line would show no voltage with 8.3 amps.
So here is the theoretical part, is there any way known where an inductor could
be used on the neutral line to use the amperage to create an electromagnet without
affecting overall voltage or amperage other than the resistance of the inductor of the
electromagnet.

You may ask why, because I theorize that if I can create magnetic
fields using waste current, or whatever you want to call it, the current that's been used
for the task at hand, then those magnetic fields may be able to be used for other purposes.
I understand why it should not work, but does it seem totally impossible?
 
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There is no waste current. Anything added into the neutral line reduces the voltage available to the heater element, so there is no free lunch going begging here. You might decide you'll wind the electromagnet of very low resistance wire, but coiled wire around a magnetic core is an inductor and its reactance robs your heater element of some voltage, again.
 
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A current, i, flowing through an inductor, L, generates a magnetic field. The energy, E, in the magnetic field is E = ½ · L · i²
That represents a loss of energy, radiated from the inductor circuit. Conservation of energy must hold. If energy is radiated, it must come from somewhere, so the circuit parameters must change to allow energy to flow through the inductor.
 
If the mains supply was DC, I think you are correct that a magnet can be obtained for nothing. Of course, the magnet, if zero resistance, stores energy but does not lose it.
 
tech99 said:
If the mains supply was DC, I think you are correct that a magnet can be obtained for nothing.
Energy must be supplied initially to manufacture a magnet, or to increase the DC current flowing through an inductor.

tech99 said:
Of course, the magnet, if zero resistance, stores energy but does not lose it.
Establishing a magnetic field in the magnetic circuit, and the nearby universe represents an initial energy investment during the change.
If zero resistance conductors are present, the magnetic field will be reflected perfectly. Those perfect conductors will prevent magnetic fields entering that superconducting space.
Where resistive conductors are present, even if far away, there will be induced eddy currents that must convert some of the changing magnetic field energy into heat. That heat energy is lost from the magnetic circuit.
 

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