It is an assumed that positive and negative electromagnetic charges,"attract" each other. But what IS charge?
19497
Is charge of something for (e.g.) an electron related to electromagnetic space if it exists due to energy, due to which it may have mass? I don't know about quantum mechanics or advanced particle models. Can anyone just simply give an intuitive idea?   EDIT I want to mean what actually gives electron charge if it is not assumed fundamental but result of some other physical phenomenon or it is  just the quantity defined to explain physical interactions?I think now it is clear
96578
When we rub our hairs with a comb, and then try to attract small pieces of paper, they're attracted by the comb. The pieces of the paper were not electrified before they were attracted. Then they might be neutral. Why does the comb attract the pieces of the paper if they're neutral, and have no influence of a specific charge on them (Pieces of paper).
73547
How can light be called electromagnetic if it doesn't appear to be electric nor magnetic?  If I go out to the sunlight, magnets aren't affected (or don't seem to be).  And there is no transfer of electric charge/electrons (as there is in AC/DC current in space).   In particular, the  (which light is supposed to be composed of) have no electric charge (nor do they have ).   I'm looking for an explanation that can be appreciated by the average non-physicist Joe.
19429
We can think that the electric field and the gravitational field operate similarly in the sense that the forms of their governing laws (namely, Coulomb's law and Newton's law respectively) are strikingly similar. The only difference one can point out is that while the electric charges come in two flavors, the gravitational masses come in just one.  Now, I have read that when a charged particle moves, the electric field lines associated with are distorted in a fashion because of the finite time required for the information about the change in the position of the charge to get propagated. And, I have led to the understanding that this is the cause of the existence of the magnetic field (and that if calculus is used it can be proven mathematically).   So (if this is true then) why doesn't the same thing happen to the gravitational field? Why is there nothing like a gravitational magnetic field? Or, is there?  Note  I have changed the language and the tone of the question massively. Although the question was fairly well received, I believe it was really ill-posed. As pointed out by ACuriousMind in the comment, the ''reason''described here behind the existence of the magnetic field is something that cannot be found a good support for. But still, due to the similarity between the equations describing their static behavior of electric and gravitational fields, one can still ask as to whether a boost would create some sort of a gravitational magnetic field if the original frame only had a static gravitational field. As the accepted answer points out, the answer is, roughly, a yes but the Maxwell-type equations for gravity aren't as well-behaved as are the original Maxwell equations of electromagnetism--one should note. In particular, the equations for gravity take the Maxwell-like form in appropriate weak limits only in some appropriately chosen gauges--and aren't Lorentz covariant.
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I'm a high school student. I love computers and electronics. Few weeks ago, I thought to build my own electronic gadget but, unfortunately I had not much knowledge in electronics. So, I decided to learn. After Googling here and there, I came across a large amount of information. Nothing, except one thing, that daunts and intimidates me is that what the term Charge means? None of the books tell what it means. Some tell that it is the basic property of the matter and just it and don't define further about it. Whereas some don't even bother to tell about it. On  it is defined as:     Electric charge is the physical property of matter that causes it to experience a force when close to other electrically charged matter.   The definition is quite bit difficult and confusing. Similarly from  Website tutorials I got a different type of definition and understanding.  From books, I came to know that we still don't know much about charges even great scientists like Sir Stephen Hawking doesn't known much about it. Is it correct? If not, then why was it written in the books (I mean here books not a book), what is its correct definition? Why majority of books don't define what charges is/are?
123277
If a thin metal plate is placed between two charges $+q$ and $+q$, will this cause a change in the electrostatic force acting on one charge due to another? What is the concept behind this? What will happen if the metal plate is thick?
99104
From Rutherfords alpha scattering, where alpha where fired at a thin peace of metal foil, he concluded that the nuclei were positively charged. He made this conclusion from the fact that alpha particles were scattered at different angles but would a negative charge not scatter the alpha the same way as a positive? As far as i can see it the scattering pattern caused by alpha been deflected of there path by an attractive force would be the same as a replusive. So why did he conclude the nucleus was positively charged??
48633
In electromagnetism books, such as Griffiths or the like, when they talk about the properties of conductors in case of electrostatics they say that the electric field inside a conductor is zero.  I have 2 questions:    We know that conductors (metallic) have free electrons which randomly moves in all directions, so how come we can talk about electrostatics which by definition means stationary charges? When the textbooks try to show why the electric field inside a conductor is zero they say let us put our conductor in an electric field. What happens then is that there will be an induced surface charge density which consequently induces an electric field within the conductor such that the total electric field within the conductor will be zero. That is perfectly understood, but my problem is the following: the original claim was that the electric field within a conductor is 0, not the electric field after putting the conductor in an external electric field it became zero. I do not understand the logic!
86879
It is fairly easy using basic special relativity to arrive at the conclusion that the magnetic force effect on nearby charges of wires carrying currents on nearby charges is only due to the length contraction in certain inertial frames from the point of view of charges, which gives rise to a perceived change in charge density. However, we structure the (classical field) laws of electromagnetism in Maxwell's laws using a B field.  My question is, is it possible to formulate Maxwell's equations only in terms of Lorentz transformed E fields? If not, why not?
79793
As far as I know, Coulomb's law of electrostatic force is applicable on two different charges situated in same medium. But if two individual charges are in different media (say one charge on a iron surface another on a plastic surface), then how does one calculate the force between them?  And if I have wrong conception , please correct me.
34955
Is there a definition of  and proper explanation of it?  It is said "Electric charge is the physical property of matter that causes it to experience a force when close to other electrically charged matter."  How is it though that matter can get charged?  Defining charge as the property of feeling a force with other charged matter seems circular.  What is charge?  Is there a non-circular definition / explanation?
115597
This question  , with very detailed answers.  After reading those answers, I am left with one more question: what is color charge?  It has nothing to do with colored light, it's a property possessed by quarks and gluons in analogy to electric charge, relates to mediation of strong force through gluon exchange, has to be confined, is necessary for quarks to satisfy Heisenberg principle, and one of the answers provided a great colored Feynman diagram of its interaction, clearly detailing how gluon-exchane leads to the inter-nucleon force.  But what is it?  To see where I'm coming from, in Newton's equation for gravity, the "charge" is mass, and is always positive, hence the interaction between masses is always attractive. In electric fields the "charge" is electric charge, and is positive or negative. (++)=+, (--)=+, so like charges repel (+-)=(-+)=-, so opposite charges attract. In dipole fields, the "charge" is the dipole moment, which is a vector.  It interacts with other dipole moments through dot and cross products, resulting in attraction, repulsion, and torque. In General Relativity, the "charge" is the stress-energy tensor that induces a curved metric field, in turn felt by objects with stress-energy through a more complicated process.  So what is color charge?  The closest that I've gotten is describing it through quaternions ($\mbox{red}\to i$, $\mbox{blue}\to j$, $\mbox{green}\to-k$, $\mbox{white}\to1$  , "anti"s negative), but that leads to weird results that don't entirely make sense (to me), being non-abelian.  Since $SU(3)$ is implicated, what part of $SU(3)$ corresponds to, for instance, "red" or "antigreen"?  (Like "positive charge" is $+e$, "negative charge" is $-e$).  What is the mathematical interaction of red and antired (like positive and negative is $(+e)(-e)=-e^2$), and what happens when you apply that interaction to red and antiblue?  (Like how electric charges interact with magnetic dipoles through their relative velocities).  If I had to point to a thing on paper and say "this here represents the red color charge", what would that thing be?  Does such a thing even exist?  In short, what is color charge?  I've had abstract algebra and group theory and some intro courses on field theory and QED, but I don't know a lot of jargon, or really a lot of algebra.  Sorry the question's so long.  Thanks for the future clarification!
3891
I recently came to know about the Conventional Current vs. Electron Flow issue. Doing some search I found that the reason for this is that Benjamin Franklin made a mistake when naming positive and negative charges. There is even this little comic about that   My question is, how can a naming convention be wrong? Perhaps I don't understand what is the actual mistake here, I don't know. But I don't see how a naming convention could be wrong or right. There is no right and wrong about that. It could've been any other name, like charge A and charge B.  I'll appreciate anyone can help me understand what is wrong in all this.
109929
We know that the protons in a nucleus are positively charged, whereas the neutrons do not possess a charge; we also know that unlike charges attract. So why does the nucleus stay intact, even though there isn't supposed to be any electrostatic force of attraction within it? Instead, why isn't there any repulsion between the protons which are like-charged?
89633
I see this sort of statement in many materials, for example :     The smallest radiating unit is a dipole, an electromagnetic point source.   and :     The simplest infinitesimal radiating element, called a Hertzian dipole…   However, none of them includes a clear explanation. Why a dipole, which is consist of 2 charges? Isn't a single non-uniformly moving charge enough?
84095
Conceptual question:  Suppose we have a configuration of point charges. If the potential of the energy of the system is negative, this means work is positive.   I'm kind of rusty with my mechanics, does the fact that the work is positive mean that to arrange the configuration you have to do work against the electric field? I.e. supply energy via some external force?  In terms of electrostatics, is there a general way of interpreting the sign of potential energy and work?
59885
So my physics teacher assigned us an article about how special relativity causes magnetism in a wire with a current, even with the low drift velocities of electrons in a current.  It seemed that the basis of the article was that magnetism is just relativistic electricity, so I was wondering how a permanent magnet worked? It makes sense to me that a moving charged particle attracts unmoving particles of the opposite charge, but how do the orbits of electrons in a magnet cause it to have a magnetic field?