Can a LRC circuit produce a net magnetic field with zero net charge flow?

In summary: Transformers wouldn't work. Alternators wouldn't work. All motors, generators, and transformers work on the principle of AC (alternating current) which means the current is constantly changing direction, and thus there is no net charge flow. Yet they all do net work.In summary, the conversation discusses the concept of creating a net squared magnetic field without a net flow of charge. The speaker suggests flipping the sign of the squared magnetic field to achieve this. However, there is a discrepancy in the calculation as the square of -10 is actually +100. The conversation also touches upon the idea of using capacitors to increase the time constant of a circuit and the possibility of using this setup to do net work with zero net charge flow
  • #1
kmarinas86
979
1
Let's say for the:

First 10 milliseconds: Current is 1 milliamp. The squared magnetic field resulting we will call "default".

1 millisecond following, last millisecond: Current is -10 milliamps. The squared magnetic field is -100 * "default".

The time average square of the magnetic field corresponds to: 10 * 1 - 1 * 100 = -90

One could then imagine the ability for an electromagnetic field made this way to do net work with zero net charge flow, provided that the time constant of the wire is larger than 10 milliseconds. Capacitors could easily increase the time constant of the circuit. The capacitors could be lined up in circuit with a low voltage battery. The circuit could intermittently connect and disconnect a higher voltage, higher current battery with the opposite polarity for a fraction of the time. If timed precisely, the charges would travel back in forth through the wire in a linear way while producing time-average squared magnetic field that is positive.

Something is wrong.
 
Engineering news on Phys.org
  • #2
kmarinas86 said:
Current is -10 milliamps. The squared magnetic field is -100 * "default".

The time average square of the magnetic field corresponds to: 10 * 1 - 1 * 100 = -90

Something is wrong.

One thing that is wrong is that the square of -10 is +100, not -100.

The rest of your post is difficult to follow. I can't tell what you're trying to say.

Does this have something to do with an earlier post where you were putting the primary and secondary of a transformer in series with a motor and commutator?

It would help if you would provide a schematic (not a picture, but a regular schematic) and tell us what you're trying to do.
 
  • #3
The Electrician said:
One thing that is wrong is that the square of -10 is +100, not -100.

Right. But this misses an important part of my point of flipping the sign. Let's go with the positive sign and see what happens:

kmarinas86 said:
Current is -10 milliamps. The squared magnetic field is -100 * "default".

The time average square of the magnetic field corresponds to:

10 * 1 + 1 * 100 = 110

To take the average we get:

110/11 = 10

So we get a net squared magnetic field without a net flow of charge.

The Electrician said:
Does this have something to do with an earlier post where you were putting the primary and secondary of a transformer in series with a motor and commutator?

No

The Electrician said:
It would help if you would provide a schematic (not a picture, but a regular schematic) and tell us what you're trying to do.

Right now I'm not trying to do anything. I just need proof that a system that has 0 net charge flow can't do net work.
 
  • #4
kmarinas86 said:
So we get a net squared magnetic field without a net flow of charge.


Right now I'm not trying to do anything. I just need proof that a system that has 0 net charge flow can't do net work.

You won't find any such proof because it isn't true. In fact, it would appear that you have just proved that it isn't true.

If it were true, then AC powered induction motors wouldn't work.
 

1. What is an LRC circuit?

An LRC circuit is a type of electrical circuit that consists of a resistor (R), inductor (L), and capacitor (C). These three components are connected in series and form a closed loop for the flow of electric current.

2. What is the significance of the netted time-averaged square of the magnetic field in an LRC circuit?

The netted time-averaged square of the magnetic field is a measure of the average strength of the magnetic field in the circuit over a period of time. It is important because it indicates the amount of energy stored in the inductor, which affects the behavior and efficiency of the circuit.

3. How is the netted time-averaged square of the magnetic field related to the net charge flow in an LRC circuit?

The netted time-averaged square of the magnetic field and the net charge flow are directly related in an LRC circuit. As the charge flows through the circuit, it creates a changing magnetic field in the inductor, which in turn affects the netted time-averaged square of the magnetic field.

4. How does the netted time-averaged square of the magnetic field change over time in an LRC circuit?

The netted time-averaged square of the magnetic field in an LRC circuit changes over time according to the behavior of the circuit. During the charging phase, the magnetic field increases as the inductor stores energy. During the discharging phase, the magnetic field decreases as the energy is released back into the circuit.

5. What factors can affect the netted time-averaged square of the magnetic field in an LRC circuit?

The netted time-averaged square of the magnetic field in an LRC circuit can be affected by various factors such as the values of the components (resistor, inductor, and capacitor), the frequency of the input signal, and the resistance of the circuit. Changes in these factors can alter the behavior and efficiency of the circuit, thus affecting the netted time-averaged square of the magnetic field.

Similar threads

  • Electrical Engineering
Replies
5
Views
1K
  • Electrical Engineering
Replies
2
Views
939
  • Electrical Engineering
Replies
6
Views
857
  • Electrical Engineering
Replies
10
Views
947
Replies
7
Views
2K
  • Electromagnetism
Replies
4
Views
1K
Replies
5
Views
2K
Replies
14
Views
1K
  • Classical Physics
Replies
15
Views
498
  • Electromagnetism
Replies
17
Views
1K
Back
Top