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Questions tagged [charge]

A fundamental property of matter which causes it to experience electromagnetic forces.

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89
votes
3answers
9k views

How does this baby rattle work?

Here's a gif showing how the balls move when I move the rattle. The circular tube hangs vertically, with the balls on the bottom. There are more images in the bottom. The balls roll freely inside the ...
75
votes
6answers
8k views

If like charges repel, why doesn't a charge break itself apart?

How can it be that, if like charges repel, they don't repel themselves? In other words, why don't charges break apart? About the possible duplicate: I want to know about charges in general, not just ...
73
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4answers
96k views

Why do same/opposite electric charges repel/attract each other, respectively?

I know plus pushes another plus away, but why, really, do they do that? On the other hand, molecules of the same type are attracted to each other. I find that weird. I do know some stuff about four ...
62
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5answers
8k views

Massless charged particles

Are there any massless (zero invariant mass) particles carrying electric charge? If not, why not? Do we expect to see any or are they a theoretical impossibility?
60
votes
11answers
41k views

Why is the charge naming convention wrong?

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 ...
57
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7answers
7k views

Does a charged particle accelerating in a gravitational field radiate?

A charged particle undergoing an acceleration radiates photons. Let's consider a charge in a freely falling frame of reference. In such a frame, the local gravitational field is necessarily zero, ...
54
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4answers
64k views

How and why do accelerating charges radiate electromagnetic radiation?

Let's consider it case by case: Case 1: Charged particle is at rest. It has an electric field around it. No problem. That is its property. Case 2: Charged particle started moving (it's accelerating)....
53
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3answers
20k views

Why is the ampere a base unit and not the coulomb?

I always thought of current as the time derivative of charge, $\frac{dq}{dt}$. However, I found out recently that it is the ampere that is the base unit and not the coulomb. Why is this? It seems to ...
51
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7answers
4k views

Why do we have an elementary charge but no elementary mass?

Why do we have an elementary charge $e$ in physics but no elementary mass? Is an elementary mass ruled out by experiment or is an elementary mass forbidden by some theoretical reason?
50
votes
4answers
21k views

Why do electron and proton have the same but opposite electric charge?

What is the explanation between equality of proton and electron charges (up to a sign)? This is connected to the gauge invariance and renormalization of charge is connected to the renormalization of ...
49
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6answers
8k views

Does a constantly accelerating charged particle emit EM radiation or not?

The Abraham-Lorentz force gives the recoil force, $\mathbf{F_{rad}}$, back on a charged particle $q$ when it emits electromagnetic radiation. It is given by: $$\mathbf{F_{rad}} = \frac{q^2}{6\pi \...
44
votes
5answers
10k views

How did physicists know that there are two kind of charges?

Problems The question I am about to make is either too stupid or hasn't bothered anyone because its obvious because I can't really find the answer anywhere. I am currently studying electricity and ...
35
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5answers
4k views

Is there oscillating charge in a hydrogen atom?

In another post, I claimed that there was obviously an oscillating charge in a hydrogen atom when you took the superposition of a 1s and a 2p state. One of the respected members of this community (...
32
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3answers
5k views

Why is spacetime curved by mass but not charge?

It is written everywhere that gravity is curvature of spacetime caused by the mass of the objects or something to the same effect. This raises a question with me: why isn't spacetime curved due to ...
32
votes
2answers
18k views

What is the net charge of the Earth?

This question arose in a seminar today about the solar wind... This is my vagueish understanding of the problem - please correct if you see errors! The 'classical' picture of atmospheric electricity ...
31
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5answers
5k views

Is this statement of conservation of charge circular?

According to Wikipedia: A closed system is a physical system that does not allow certain types of transfers (such as transfer of mass and energy transfer) in or out of the system. According to my ...
29
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2answers
2k views

Can the center of charge and center of mass of an electron differ in quantum mechanics?

Traditionally for a free electron, we presume the expectation of its location (place of the center of mass) and the center of charge at the same place. Although this seemed to be reasonable for a ...
27
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8answers
6k views

How can neutral atoms have exactly zero electric field when there is a difference in the positions of the charges? [duplicate]

It is said that atoms with the same number of electrons as protons are electrically neutral, so they have no net charge or net electric field. A particle with charge cannot exist at the same position ...
27
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3answers
3k views

Detection of the Electric Charge of a Black Hole

By the "No Hair Theorem", three quantities "define" a black hole; Mass, Angular Momentum, and Charge. The first is easy enough to determine, look at the radius of the event horizon and you can use the ...
26
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1answer
947 views

Overcharging a black hole

Hubeny's 1998 paper got a lot of people interested in determining whether cosmic censorship can be violated by dropping too much charge onto a black hole. It suggested that you might be able to get a ...
23
votes
5answers
3k views

Far away from a charged conductor, the field is like a point charge. Where's the point located?

In the framework of classical electrodynamics, at distances much greater than a conductor's dimension, the field ought to approach that of a point charge located at the conductor. But where at? For ...
23
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1answer
6k views

Origin of electric charge

Baryons have charges that are the result of a polynomial calculation of their building blocks (quarks)'s fractional charges. But what gives these quarks electric charges? What interactions do they ...
23
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3answers
1k views

How is the energy loss by an accelerating charge expressed in the equations of motion?

I understand how, and why, an accelerating charge emits radiation, and loses energy in the process, as well as the Larmor formula for the power, and its derivation. However, in classical mechanics, ...
22
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4answers
3k views

Why don't loop currents produce light?

If a charge travels in a circle it must accelerate, thereby producing EM. However, a wire in a circular loop is analogous to many charges moving in a circle. So, why don't circular currents produce ...
21
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8answers
9k views

How can a battery charge up another battery to a higher percentage?

Say I have my phone on 5% and a large battery pack on 35% and I charge the phone. By the end the phone is on 100% and the pack is on 12%. How can the battery pack charge the phone up to a higher ...
21
votes
7answers
3k views

Paradox with Gauss' law when space is uniformly charged everywhere

Consider that space is uniformly charged everywhere, i.e., filled with a uniform charge distribution, $\rho$, everywhere. By symmetry, the electric field is zero everywhere. (If I take any point in ...
20
votes
8answers
11k views

Why is capacitance defined as charge divided by voltage?

I understand that capacitance is the ability of a body to store an electrical charge and the formula is $C=\frac{Q}{V}$. What I don't understand, however, is why it is defined as coulomb per volt. Of ...
19
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4answers
6k views

Can a third type of electrical charge exist?

Upon reading my book on physics, it mentions that there are only two discovered types of electric charges. I wonder if there could be a third type of elusive charge, and what type of effects could it ...
19
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3answers
3k views

What is the symmetry which is responsible for preservation/conservation of electrical charges?

Another Noether's theorem question, this time about electrical charge. According to Noether's theorem, all conservation laws originate from invariance of a system to shifts in a certain space. For ...
19
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3answers
1k views

Do accelerated charges radiate or not? [duplicate]

This questions has been asked all over the net (here included) but I can't find a satisfactory answer or discussion. Some say it does not radiate if the acceleration is caused by a uniform gravity ...
18
votes
4answers
15k views

What is charge? [duplicate]

I know this isn't the right place for asking this question, but in other places the answers are so awfull.. I'm studying eletricity, so, I start seeing things like "charges", "electrons has negative ...
17
votes
3answers
5k views

If electrons were positive and protons were negative, would life be different? [duplicate]

This was a question on a worksheet during my first week in a class on Electromagnetism. The answer is essentially: No. Life would be no different if electrons were positively charged and protons ...
17
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6answers
8k views

Why isn't there a centre of charge?

When determining the gravitational attraction between 2 solid bodies, we can simplify computations by taking their masses to be concentrated at their respective centres of mass. However, had they been ...
17
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1answer
1k views

Do neutrons exhibit momentary small charges due to the movement of its quarks?

So in a similar way to electrons moving in atoms, causing induced dipole-dipole interactions, can neutrons momentarily attract or repel?
16
votes
4answers
2k views

Negative mass effect?

What's wrong with the following argument to "produce" negative mass?: Consider two charged bodys of weight $m,M$ of distance $r$ with the electric charge $Q$ and $-Q$. Then the energy of this system ...
16
votes
6answers
20k views

How is possible for current to flow so fast when charge flows so slow?

How is it possible for current to flow so fast when charge flows so slowly? We know electrons travel very slowly while charge travels at ~the speed of light.
15
votes
3answers
1k views

What's the deepest reason why QCD bound states have integer charge?

What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, ...
14
votes
2answers
3k views

Which oil was used by Robert A. Millikan in his oil drop experiment?

I need to know which oil was used by Robert A. Millikan in his oil drop experiment, i.e.name of oil or chemical formula of the oil molecule.
14
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2answers
2k views

How electromagnetic waves are created?

Macroscopically, electromagnetic waves are produced by a changing dipole or an oscillating charged particle as shown below: In this case, the frequency of the electromagnetic radiation is equal to ...
14
votes
2answers
696 views

Is there any theory for origination of charge?

We have a theory of a Higgs field that describes how a particle gets mass. Since mass and charge both are intrinsic properties of a particle, is there any similar theory for how particles get electric ...
13
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5answers
1k views

What's the reason behind the current remaining the same after passing by a resistance?

I've been wondering why does this really happen, I mean by intuition if electrons are driven by EMF (ignoring wire's resistance), $n$ coulombs would pass by a point per second, until they encounter ...
13
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3answers
2k views

How did physicists know that only negative charges move?

I have phrased similarly another question about how physicists knew that two charges exist, positive and negative. The purpose of the question is not necessarily to educate me historically. It's just ...
13
votes
3answers
21k views

Do moving charged particles have both magnetic and electric fields?

Consider a charged particle (electron or proton) at rest. It is surrounded by its own electric field. Now consider an electron moving with certain velocity. Is there still an electric field around it?...
13
votes
3answers
10k views

Why do quarks have a fractional charge?

I am aware that evidence exists that strongly suggests the existence of quarks and do not doubt it. It is just simply really weird to me that they can have a fractional charge. While other ...
13
votes
2answers
1k views

Electric charge neutrality of the Universe: evidences and theories

I've always wondered why the number of protons in the Universe exactly matches the number of electrons. They are such different particles with totally different cross sections. So, first of all, is ...
13
votes
1answer
390 views

How can I find the position of an image charge when the boundary is parabolic or hyperbolic?

If the position of some charge $Q$ is known, the boundary condition is $u=0$ on some parabolic surface, and we know the image charge has its electric volume of $Q'$, then how can I determine the ...
12
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5answers
3k views

Have we directly observed the electric component to EM waves?

For example, has anyone has directly observed charges oscillating due to standing EM waves? I am particularly interested because it'd demonstrate that radiation has a transverse electric component to ...
12
votes
3answers
3k views

How many kinds of “weak charges” exist?

For electricity, we have one charge, for the strong force three. How many are there connected to the weak force? Three, because of the W- and Z-particles? For the weak force, there is the isospin, ...
12
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3answers
2k views

Electron charge from Millikan's oil drop experiment

Nearly every explanation of oil drop experiment I ever found concludes along the lines of The charge $q$ on the droplets were thus measured, and were all found to be integral multiple of $1.6 \cdot ...
12
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4answers
2k views

Why are there no elementary charged, spin-zero particles?

In the spirit of a related inquiry, I would like to know if there's a basis for understanding why there aren't any elementary particles that have non-zero electric charge but zero spin? Can such a ...