# Fundamentally, what is an electric field?

• czaroffishies
In summary: The concept of an electric field is used to explain how electric charges interact with each other and with other forces in the universe.In summary, an electric field is a mathematical model used to predict the behavior and interactions of electric charges in a given space. It is not a tangible physical entity, but rather a representation of the forces at work in the universe. The concept of an electric field is used to explain the behavior of electric charges and their interactions with other forces.
czaroffishies
I understand the definition of an electric field as a property of space surrounding a charge, but what exactly is this property? You can think about gravity as objects distorting bend-able space... but is there an analogous explanation for electric fields? Or at least some ideas?

In Atomic Theory the polarity of charge q is defined as an electron q = -e and the proton q+ = +e, where in classical physics the q+ is called a test charge.

The static electric field E predicts the motion of a test charge q+ in the presence of the field. The force F on a charge q is:

F = qE where q is a quantity of charge inserted at a point in the E field.

The field itself is created by some spatial distribution of charge, typically much larger than the small charge q in question, otherwise the charge in question changes the shape of the E field!

Welcome to PF!

czaroffishies said:
I understand the definition of an electric field as a property of space surrounding a charge, but what exactly is this property? You can think about gravity as objects distorting bend-able space... but is there an analogous explanation for electric fields? Or at least some ideas?

Hi czaroffishies! Welcome to PF!

I'll leave someone else to answer the main question, but I'll just point out that an electric field is really just three components of the six-component electromagnetic field.

Hi SystemTheory!

Yes, but that doesn't answer what the field is (especially since it can exist in a vacuum).

In a vacuum human beings don't exist to infer that electromagetic fields exist in a vacuum!

In all such problems involving gravity or electromagnetic fields the working definition implies a region of mass or static charge or moving charge inside some system boundary distributed in space.

A field is used to describe interactions at a distance. What exactly is the field? A mathematical model one can rely upon to predict action at a distance based on past observations. No one knows for sure what causes action at a distance, and perhaps, no one ever will.

I look at it this way. If electrons dance in a dipole antenna over here (transmitter) they also dance at a much smaller magnitude in a similar antenna over there (receiver). The model that helps predict such behavior is called electromagnetic field and wave theory.

SystemTheory said:
In a vacuum human beings don't exist to infer that electromagetic fields exist in a vacuum!

In all such problems involving gravity or electromagnetic fields the working definition implies a region of mass or static charge or moving charge inside some system boundary distributed in space.

A field is used to describe interactions at a distance. What exactly is the field? A mathematical model one can rely upon to predict action at a distance based on past observations. No one knows for sure what causes action at a distance, and perhaps, no one ever will.

I look at it this way. If electrons dance in a dipole antenna over here (transmitter) they also dance at a much smaller magnitude in a similar antenna over there (receiver). The model that helps predict such behavior is called electromagnetic field and wave theory.

I asked my professor about this and he didn't have an answer, so I don't really expect anything definite like we have for gravity. It would be nice if someone happened to know something neither my professor nor I know, but I am aware that that's not likely.

Mostly I was pushing for philosophical conjecture, I suppose. ;)

SystemTheory said:
In a vacuum human beings don't exist to infer that electromagetic fields exist in a vacuum!

In all such problems involving gravity or electromagnetic fields the working definition implies a region of mass or static charge or moving charge inside some system boundary distributed in space.

A field is used to describe interactions at a distance. What exactly is the field? A mathematical model one can rely upon to predict action at a distance based on past observations. No one knows for sure what causes action at a distance, and perhaps, no one ever will.

I look at it this way. If electrons dance in a dipole antenna over here (transmitter) they also dance at a much smaller magnitude in a similar antenna over there (receiver). The model that helps predict such behavior is called electromagnetic field and wave theory.
http://en.wikipedia.org/wiki/Action_at_a_distance_(physics )

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Asking what an electric field, or any physical concept, really is gets you into difficult territory, and besides, it's not really part of physics. At its core, physics only explains observations; it doesn't deal with the mechanisms behind those explanations (although sometimes we speculate about the mechanisms when it makes the science easier to understand). In other words, physics will tell you how things behave, but it won't tell you anything about their underlying nature that isn't reflected in their behavior. In fact, as far as a physicist is concerned, once you know how something behaves, you know all there is to know about what it is; anything further is just idle speculation. (Which can be fun, don't get me wrong, but it's not really science) And we do have a mathematical model for how the electric field behaves, so as far as physics is concerned, that's what it is - it's a value at every point in space that specifies what the force on a unit test charge at that point would be.

I think I even confused myself writing (and rewriting) that... this is why I stick to the math ;-)

If there were a really simple way of stating what an Electric Field 'really is' then it would be on page one of every textbook. The fact is that it isn't simple enough to dismiss with a single statement. Physics does its best to reduce things to their basic nature but there is a limit. Simple analogies can be a snare and a delusion - leading to further misconceptions for the unwary.
The best you can hope for is statements like "An Electric Field is a thing that causes a force on a charge". The idea of mass / gravity representing a 'bend in space' is useful but only as a simple picture and an analogy. It doesn't mean that it is 'really' what is happening - the concept of 'really' is very shaky in studying the World. It is what it is and that's all.

sophiecentaur said:
If there were a really simple way of stating what an Electric Field 'really is' then it would be on page one of every textbook. The fact is that it isn't simple enough to dismiss with a single statement.

I didn't expect anyone to. I mostly just thought it would be nice if someone knew. Back to my gravity example, my introductory mechanics book didn't post "curvature of spacetime" everywhere when the gravity discussion came up. But really, I just like ideas. The math is great, but the ideas are what really keep me going, and I figured there would be at least a few people out there who have thought about this and had their own crazy theories!

sophiecentaur said:
It is what it is and that's all.

(Even if I was seeking more than philosophical entertainment, what would be wrong with that? Physical truths can always be expanded on. It kind of seems like that's what characterizes the progress of physics, anyway. :) )

diazona said:
Asking what an electric field, or any physical concept, really is gets you into difficult territory, and besides, it's not really part of physics. At its core, physics only explains observations; it doesn't deal with the mechanisms behind those explanations (although sometimes we speculate about the mechanisms when it makes the science easier to understand). In other words, physics will tell you how things behave, but it won't tell you anything about their underlying nature that isn't reflected in their behavior. In fact, as far as a physicist is concerned, once you know how something behaves, you know all there is to know about what it is; anything further is just idle speculation. (Which can be fun, don't get me wrong, but it's not really science) And we do have a mathematical model for how the electric field behaves, so as far as physics is concerned, that's what it is - it's a value at every point in space that specifies what the force on a unit test charge at that point would be.

I think I even confused myself writing (and rewriting) that... this is why I stick to the math ;-)

Hye czarroffihies ... just let me say that I agree with diazona... but that I like your way to ask. I don't know how old you are and you don't have to tell me it. I would only like to insist on that marveillous moment of the life (about 14 - 20) when we have to leave our quest for a deep understanding of what the universe is and exchange it for a more efficient behavior... in some way leaving the magic world for a rationalistic one. We don't know what the worls really is but we try to guess the relationship between the objects contained in the world that we are perceiving. So I don't know what an electric field is. Sorry.

I'm not sure where all this is discussion is coming from, but it is not a mystery as to what fields are. The electromagnetic force is mitigated by photon exchange.

What is measurement except just a series of locations of events in time and space. The ideas of charge, fields, or photons are just models to predict (or explain) distance/correlation between events: modification of distance if you will. One might consider GR more elegant because it uses time/space itself to explain those modifications.

Pengwuino said:
I'm not sure where all this is discussion is coming from, but it is not a mystery as to what fields are. The electromagnetic force is mitigated by photon exchange.

Hi Pengwuino!

(you mean "mediated" )

No, as a matter of physics, the electromagnetic force is not mediated by photon exchange.

No photons are exchanged.

"mediated by photons" is just mathematicians' way of saying that the transition amplitude is an infinite series of integrals which include creation and annihilation operators of every possible momentum of a zero-mass spin-1 particle.

(all other forces, btw, use non-zero masses for this "vector boson")

Furthermore, the electromagnetic force is also "mediated by electrons" (and positrons) … the transition amplitude also includes creation and annihilation operators of every possible momentum of a particle with the mass of an electron (and with spin-1/2 and charge ±1 and lepton number 1).

(we could call them the "vector fermions" of the force, but I don't think anyone actually does)

In fact, most Feynman diagrams contain twice as many virtual electrons (or positrons) as virtual photons, for the obvious reason that each vertex contains twice as many.

No electron or positron or photon is harmed, or even actually present, in the process.

The mystery is why the electromagnetic force uses the particular mass of an electron (and indeed the particular, zero, mass of a photon) when

i] the electron mass seems entirely arbitrary

ii] no particle with that mass (electron or positron or photon) is actually involved!​

An electric field "alters" space as described in Conceptual Physics book. If a charge to which the field is attributed moves, there is further alteration of space and this is called magnetic field.
I hope this helps.
Sridhar

Electric field lines to not have to terminate on charges. A good example is the azimuthal electric field surrounding a region that has a changing magnetic field (dB/dt); i.e., Faraday Law induction. two applications include the secondary windings on ac transformers, and betatron particle (electron) accelerators. In both cases, the electric field lines terminate on themselves, and represent a modification to space by the changing magnetic field (dB/dt).
Bob S

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Electric field lines to not have to terminate on charges.

My understanding is that the electrostatic field lines must terminate on a region of static charge. This is similar to gravity terminatining on a region with mass, although I am not familiar with the theory of gravity waves (time delay in the influence of gravitational force).

The motion of charge (described somewhere, somehow) creates a magnetic field. This couples an electric field in space. Therefore, there is an electromagnetic EM field "caused" by charge motion described somewhere in the problem characterization.

The rules for EM fields are not the same as for electrostatic fields in accord with Bob's statement.

Maxwell's Equations reduce to the static electric field when charge is static, as I recall. They characterize the EM field when charge is in motion based on the particular geometry and properties of materials involved. But it's been a while since I solved an EM problem ...

http://en.wikipedia.org/wiki/Maxwell's_equations

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SystemTheory said:
My understanding is that the electrostatic field lines must terminate on a region of static charge. This is similar to gravity terminatining on a region with mass, although I am not familiar with the theory of gravity waves (time delay in the influence of gravitational force)...
Maybe the electric field lines from Faraday's Law are electromagnetic and not electrostatic, but they don't terminate on electric charges.

The Sun's gravitational field lines at the Earth don't seem to be diminished by the Moon passing between the Earth and the Sun. Do the Sun's gravitational field lines pass through the Moon without terminating?
Bob S

Interference patterns exist in EM fields. The classic example of particle-wave duality is light (or electrons) passing through a double-slit.

http://en.wikipedia.org/wiki/Double-slit_experiment

I'm not sure how this applies to gravity or electrostatic field models. I'll think about your question re. the moon interfering with the Sun's gravitation on the Earth ...

czaroffishies said:
I understand the definition of an electric field as a property of space surrounding a charge, but what exactly is this property? You can think about gravity as objects distorting bend-able space... but is there an analogous explanation for electric fields? Or at least some ideas?

The OP asks about the similarities between General Relativity and Electromagnetic waves, so I'm posting this link, which has a number of (apparently informed) papers near the bottom on Gravity and Relativity:

http://www.metaresearch.org/home.asp

I've always wondered how space instantaneously "knows" how to bend the instant I drop some mass into a region? In other words, Newton's view of gravity is instantaneous and I'm not sure how Relativity impacts this assumption, but admittedly, I've never thought much about it.

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Well, energy/momentum is something, or represents the effect of something. And whatever that something is everything is made of it.

My interpretation/speculation (and that is all it is) is that "something" is structures in space-time. Or, in another way, alterations to space-time. We see that plainly in gravity as space-time has a structure causing gravity. By loose induction, all physical phenomena, including EM fields, would be different types of structures of space-time. Now, I think string theorist attempt to actually codify this but I don't know much about it. It would have to be a structure which impacts each type of particle differently, where as GR impacts everything the same.

http://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory" proposed that the electric field potential could be elements of the metric for 5 dimensional spacetime.

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but what exactly is this property?

All 'normal' matter (to be precise) is made up of charged and uncharged particles.

An electric filed which exists in space simply has this property to apply force on these charged particles.

Two important properties are 1. The electric field due to a charge fills the entire universe and 2. The electric field penetrates through matter...In short, where there is a charge there is an electric field around it.

sridhar10chitta said:
Two important properties are 1. The electric field due to a charge fills the entire universe and 2. The electric field penetrates through matter...In short, where there is a charge there is an electric field around it.

I'm afraid point 1 is violating quantum physics and so that actually does not happen; but cause I'm not into that subject, I can't explain further.

How does that violate quantum physics? You are saying at some large distance from a source you would no longer be able to make a measurement of the electric field?

czaroffishies said:
I didn't expect anyone to. I mostly just thought it would be nice if someone knew. Back to my gravity example, my introductory mechanics book didn't post "curvature of spacetime" everywhere when the gravity discussion came up. But really, I just like ideas. The math is great, but the ideas are what really keep me going, and I figured there would be at least a few people out there who have thought about this and had their own crazy theories!

(Even if I was seeking more than philosophical entertainment, what would be wrong with that? Physical truths can always be expanded on. It kind of seems like that's what characterizes the progress of physics, anyway. :) )

I am responding a little bit late, but late is better than never. Well, the reason that nobody has answered you question what is "charge" is that there is no such a thing. Even in QFT the potential is put in there by hand. My idea is that the so called charge (effect) is only due to interacting particle based on the mass. for example the proton pulls on the electron wavefunction toward itself (as per the interaction for high potential particle-equivelent to high mass- in my website), the potential is automatically is introduced inthe system. If the particles waves are of comparable size then the waves of the particles facing each other get exponentially chupped of in front of each other forcing the wave to back off ie. repultion. That is why I think QM and GR are not fundamental but manage to describe processes very accuratly. I hope my system does that and more.

http://www.qsa.netne.net

## 1. What is an electric field?

An electric field is a physical field that surrounds an electrically charged particle or object. It is a force field that can exert a force on other charged particles within its proximity.

## 2. How is an electric field created?

An electric field is created by electric charges, either positive or negative. When two charges are placed close to each other, they create an electric field between them. The strength of the field is determined by the magnitude of the charges and the distance between them.

## 3. What is the difference between electric field and electric potential?

Electric field is a vector quantity that represents the force per unit charge at a certain point. Electric potential, on the other hand, is a scalar quantity that represents the potential energy per unit charge at a certain point. In simpler terms, electric field describes the strength and direction of the force, while electric potential describes the energy of the electric field at a specific point.

## 4. How is the strength of an electric field measured?

The strength of an electric field is measured in units of volts per meter (V/m). This measures the amount of force (in volts) exerted on a unit of charge (in meters). The greater the voltage per meter, the stronger the electric field is at that point.

## 5. What are some real-life applications of electric fields?

Electric fields have a wide range of applications in our daily lives. Some examples include charging our electronic devices, generating electricity in power plants, and controlling the movement of electrons in electronic circuits. They are also used in medical procedures such as electrocardiograms and in industrial processes such as electroplating.

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