# A few questions regarding B/E-fields in practical circuitry

I have been trying a few learning resources to help unlearn some of the notions that electrons flow through as energy.

Chiefly this resource is what I have used:
Amasci - IN A SIMPLE CIRCUIT, WHERE DOES THE ENERGY FLOW?

My questions are:

Does energy transfer from the battery through the load through B-fields, i.e. "electromagnetic current" and not really through any other means? Is "Electricity" simply heavily concentrated electromagnetic fields when flowing through a conductor? For example, an arc between two high voltage electrodes is the electromagnetic energy jumping the gap, the heat and light of the arc are just by-products of this?

The resource shows an E-field existing between the circuit path: efields

What if the path were something like a wire surrounded by a magnetic insulator, would the e-field be pointless, or not "care" that anything is blocking it just existing on either side to create a difference in potential?

Would there be less energy available? I am greatly interested in how energy is transferred through the wire, at least correctly.

Does the insulation of wiring (i.e. plastic) also help in reflecting some of the energy so that it does not drop over a distance? This could sense, being that an exposed wire may pick up energy in the air, and an insulated keep it out.

• Your link or your understanding of this point is incorrect: "The resource shows an E-field existing between the circuit path: efields". Your link points to the POYNTING FIELD. This shows you the flow of energy. It is proportional to the cross product of the electric (E) and magnetic (B) fields, i.e. E x B Commented Dec 19, 2011 at 4:11

Does energy transfer from the battery through the load through B-fields, i.e. "electromagnetic current" and not really through any other means?

The vast majority of energy transfer is from the electromagnetic fields (E & B-Fields which are coupled). There might be some fringe situations where ion or electron (-e) transfer contribute to total energy transfer, but I can't think of any off the top of my head. That's the primary point of the page you've linked, and the POYNTING diagram in figure 7 should show you the energy transfer (that's what they do). Notice that it shows all arrows pointing to the load and away from the source.

Is "Electricity" simply heavily concentrated electromagnetic fields when flowing through a conductor? For example, an arc between two high voltage electrodes is the electromagnetic energy jumping the gap, the heat and light of the arc are just by-products of this?

Well, this question isn't well phrased, so I'm going to assume that you are asking what is the principal method of energy transfer, which is the same as your first question.

Directly speaking, electricity is the flow of charged particles. The other point to make here is that the electromagnetic fields flow AROUND a conductor, not through it. Someone might nitpick about this, but it's essentially true.

As to the arc, it is caused by the electromagnetic fields exciting atoms of air to the point where you see a reaction. This is akin to asking, "What is fire? Is it just a byproduct of Oxygen combining with Carbon?". Yes, it is, but what you see is an excitation of gas molecules around that combustion.

What if the path were something like a wire surrounded by a magnetic insulator, would the e-field be pointless, or not "care" that anything is blocking it just existing on either side to create a difference in potential?

Would there be less energy available? I am greatly interested in how energy is transferred through the wire, at least correctly.

Here you need to understand that E and B fields are COUPLED. So, no, the E-Field wouldn't not (double negative, sorry) "care", it would be affected and so would the flow of electrons in response. What you've mentioned here would actually be a passive inductive element in the circuit! Look up the theory around inductors and you'll get a good idea of what's happening here.

Does the insulation of wiring (i.e. plastic) also help in reflecting some of the energy so that it does not drop over a distance? This could sense, being that an exposed wire may pick up energy in the air, and an insulated keep it out.

I'm not exactly sure how to respond to that one. The real job of the insulation is to keep the circuit in isolation from the environment, so your second sentence makes some sense, but reflecting energy isn't the appropriate way to think of what it is accomplishing.

• Actually, thinking more about it, Van de Graff generators use ion or e- transfer as the primary means of energy transfer, so there are probably lots of examples where E&B-Fields aren't the primary contributor to energy transfer. But in most electric circuitry, stick to the above. -BP Commented Dec 19, 2011 at 6:57
• how often is a van de graff generator used in the real world. In general real world devices use E fields focused threw a conductor and magnetic fields forming a curled loop around the conductors. Commented Dec 19, 2011 at 7:14

If by "electricity" you mean "joules of electrical energy" then yes, "electricity" is nothing but concentrated e-fields and b-fields. It's the same thing as audio and video signals traveling along coax cables. With wires, the energy can leap along a column of mobile charge carriers, while the charge carriers themselves only wiggle back and forth.

Plastic insulated lamp cord? Yes, the plastic would tend to concentrate the e-field between the wires. It would also change the speed at which the EM energy moves along. But mostly the fields are concentrated by having the two wires placed very close together. That's basically how Ethernet "twisted pair" cables work. The wires behave like the two plates of a capacitor, or like a very stretched-out single-turn inductor. Where are the strong fields in a capacitor? Between the plates. And in an inductor? In the donut-hole.

But wire-pairs are very good at guiding EM energy, and the usual losses aren't from radiation. The EM fields don't leave the wires and fly off into space. Instead the losses are "frictional," from the ohms of the metal (and perhaps from high-freq dielectric losses in the plastic.)

A leaping spark is not a jumping of EM energy. After all, a spark is a resistor, the carriers in the plasma aren't flowing near velocity c, and the EM energy actually flows inwards into the spark from all directions.

Note that this article was written based on the following idea: explain the material in undergrad physics texts to the general public wo/relying on equations. Pull a Feynman, Red-book style. Sit kids down and say "look, this is how it really works." Oddly, the correct EM description of simple circuits is really only taught in undergrad fields/waves courses, antenna design engineering texts, etc., but rarely mentioned in circuit design courses. We all pretend that amperes equals watts, and pretend that energy flows inside the metal. Nope, wrong.

So I took the basic EM info, stripped out the math, and described it using words and some field diagrams. The Poynting diagram shows us the location of the flowing joules. The central idea is simple: descriptions of EM waves propagating on a 2-wire waveguide are identical to descriptions of simple circuits, since 2-wire waveguides have no boundary in low frequency, and the math works fine all the way down to DC. As far as I know, no textbook author ever tried this in K12 books. If you haven't encountered it before, it looks very weird ...and many of us haven't encountered it before. (JD Kraus does a bit of it in his text "Electromagnetics," but even most fields/waves texts avoid Poynting and pictures, and stick with the math.)

An HF transmitter sending RF wattage along a conductor pair to a distant dummy load? That's identical to a 60HZ generator powering an electric heater. Or instead use a battery and a light bulb, and it's no different: the energy isn't inside the electrons or trapped within the metal.

Won't this be confusing to kids? YES! This isn't for classroom work. You shouldn't be trying to memorize it for exams. Instead it's for anyone who thinks that basic electricity is contradictory and confusing, or thinks that grade-K12 books aren't giving the straight story. I've repeatedly discovered that many of the contradictions are caused by simple physics info which is declared "too advanced" and left out.

• "We all pretend that amperes equals watts" well perhaps not all of us ;-) Commented Dec 19, 2011 at 14:00
• > not all of us Be careful not to change the context: if someone believes that the energy flows inside the wires, then they're doing just as I described: pretending that watts aren't much different than amps. But in fact watts are completely different (they're as different as sound is from air.) This difference is illustrated well when we discover that, while current is inside the metal, the energy-flow is outside. Commented Oct 1, 2013 at 7:16

You seem to have some general confusion. Part of this may be from the fact that you are trying to lump electric (E) and magnetic (B) fields together. They are definitely linked, but in ordinary circuits it is simpler to understand what is going on by looking at the E field only except when working with inductors. Things like wires, resistors, and capacitors are simpler to understand from the E field point of view.

Start out by understanding voltage sources and resistors. These defined by Ohm's law. From that you can also track how charges move around (current is charge movement per time), and energy movement. Charge flow (current) and energy flow are not the same thing.