# Theoretical question about an electromagnet in an AC circuit

• Wattif
In summary, the magnetic field generated by a current through an inductor can be used for other purposes, but it requires supplying energy to start the process.
Wattif
TL;DR Summary
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?

Last edited by a moderator:
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.

DaveE, Asymptotic, anorlunda and 1 other person
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.

## 1. How does an AC circuit affect the strength of an electromagnet?

In an AC circuit, the strength of an electromagnet is constantly changing as the direction of the current flow alternates. This is because the magnetic field produced by an electromagnet is directly proportional to the amount of current flowing through it. As the current changes direction in an AC circuit, the strength of the magnetic field also changes, resulting in a fluctuating strength of the electromagnet.

## 2. What factors affect the strength of an electromagnet in an AC circuit?

The strength of an electromagnet in an AC circuit is affected by several factors, including the amount of current flowing through the circuit, the number of coils in the electromagnet, and the type of core material used. Additionally, the frequency and voltage of the AC current can also impact the strength of the electromagnet.

## 3. How does the frequency of an AC current affect the behavior of an electromagnet?

The frequency of an AC current determines how quickly the direction of the current flow changes. As the frequency increases, the direction of the current changes more rapidly, resulting in a stronger and more consistent magnetic field. This means that a higher frequency AC current will produce a stronger electromagnet compared to a lower frequency AC current.

## 4. Can the strength of an electromagnet in an AC circuit be controlled?

Yes, the strength of an electromagnet in an AC circuit can be controlled by adjusting the amount of current flowing through the circuit. This can be done by changing the voltage or resistance in the circuit. Additionally, the number of coils in the electromagnet and the type of core material used can also be adjusted to control the strength of the electromagnet.

## 5. How does an AC circuit affect the magnetic field around an electromagnet?

In an AC circuit, the magnetic field around an electromagnet is constantly changing and expanding and collapsing. This is because the alternating current causes the magnetic field to alternate as well. As a result, the magnetic field around the electromagnet will be constantly fluctuating, with the strength and direction changing as the current changes direction.

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