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

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1answer
421 views

Semiconductor problem: how much Boron is required to establish a certain amount of charge carrier density

The problem description is as follows: Boron is used to dope 1 kg of germanium (Ge). How much boron (B) is required to establish a charge carrier density of 3.091 x 10^17 / cm^3. One mole of ...
7
votes
1answer
5k views

Does a positive or negative charge attract a neutral object?

Three objects are brought close to each other, two at a time. When objects A and B are brought together, they attract. When objects B and C are brought together, they repel. From this, we conclude ...
3
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1answer
420 views

What determines how much electrical charge an object can hold?

What determines how much electrical charge an object can hold? Does increase voltage force more electrical charge to be store in an object (Van de Graaff generator), since electric field increase as ...
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1answer
45 views

Electron-Positron Annihilation: How is charge conserved at the verticies?

How is reaction possible? The verticies do not conserve charge. Also, why is the arrow for the positron pointing downwards when as time increases, the positron should move towards its vertex? Sorry, ...
4
votes
1answer
280 views

What makes *electric* charge special (wrt. CPT theorem)?

I'm wondering why the 'C' in CPT - charge conjugation - refers specifically to electric charge. Of course you could say that C is just defined as $e^+ \leftrightarrow e^-$... but there has to be ...
3
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1answer
3k views

Charge inside conductor

I know that the $E$ field inside a conductor is zero. What happens if I put a source of charge inside the conductor? Say the conductor was spherical centered on the origin and there exists a charge ...
0
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1answer
41 views

Are $Q1$ and $Q2$ attracted or repelled to the sphere shown in the figure below? [on hold]

Can you tell from the image below if Q1 and Q2 are attracted or repelled. Will Q2 only be attracted to the sphere if Q2 is enough bigger than Q1? Will the positive charge inside the shell attract ...
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0answers
18 views

Find direction and magnitude of net electrostatic force on a point charge [on hold]

Question: Find the direction and magnitude of the net electrostatic force exerted on the point charge $q_2$. Let $q = +2.4μC$ and $d = 33cm$. What I tried: I used the formula $F = kq_1q_2/d^2$ to ...
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3answers
99 views

Can two electrons attract each other?

Due to electrostatic repulsion the two electrons will repel each other as they both possess similar charges, lets leave gravitational attractive force out of the picture my question is can there be ...
-1
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2answers
42 views

How can we prove that electric field originate from and terminate on charge using Gauss Law?

We already know that electric field originate and terminate on charge only and they doesn't make any closed path. But is it possible to prove this statement using Gauss Law ? If yes then how ?
0
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1answer
40 views

What is the distribution of charge on two conducting spheres?

There are two conducting spheres of charges $Q_1$ and $Q_2$ and respective radii of $r_1$ and $r_2$ with center-to-center separation of $L$. Can the distribution of charge on each of the conducting ...
0
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2answers
816 views

Gauss Theorem:Electric field of an uniformly charged non-conducting spherical shell

I want to know the electric field of an uniformly charged non-conducting spherical shell. I know that in case of conductors(metals),the sphere can be shell or it can be solid,but in both the cases ...
0
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2answers
739 views

How do I express the interaction energy between two charged spheres?

Consider two identical insulating spheres each with radius $R$ and uniform charge $Q$ through their volume. They are separated from their centers by a distance of $d>2R$. Here is my general ...
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vote
1answer
52 views

Why can't I measure electric potential from source to point according to this formula

The formula for electric potential of points A and B in the presence of an electric field due to a point charge where $R_a$ and $R_b$ are the distances from source to point A and B respectively is: ...
1
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1answer
111 views

Upper limit to electric charge confinement?

The following questions are not intended for conventional capacitors (which stores excess charge on the outside surface), rather a type of hypothetical capacitor which is designed to confine charge by ...
0
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3answers
59 views

Is it possible that the charged sphere can lose mass by adding electron?

While studying Electrostatics, I was wondering about whether a charged sphere gains or loses mass while just adding electrons? If it is possible then the negatively charged sphere will have more mass ...
0
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1answer
17 views

Potential difference of conductor with induced load

If a metallic sphere is grounded and close to a positive charge q, it will be charged with -q. Let's say that the electrons will arrive through the grounding. This charge will cover the surface of the ...
2
votes
1answer
79 views

Charge operator for Dirac spinor

In QED, the gauge transformation which acts upon a fermionic field $\psi$ is $$\psi'(x)= e^{i \alpha(x) Q}\psi(x)$$ where $Q$ is the charge operator. Most of the time it's just written as $$\psi'(x)= ...
7
votes
5answers
8k views

How can I prevent my son building up static on his trampoline? [duplicate]

Whenever my three year old son plays on his trampoline, it doesn't take very long for him to start building up a significant amount of static electricity. His hair stands on end (which is quite ...
0
votes
1answer
50 views

Efficiency of an electric motor? [closed]

Question: An electric motor runs off a 12V d.v. supply and has an overall efficiency of 75%. Calculate how much electric charge will pass through the motor when it does 90J of work. Can someone tell ...
1
vote
1answer
28 views

Capacitors and Voltage

Imagine if I have a capacitor, connected to a battery of $12 V$. After charging the capacitor, I increase the plate separation. Then my capacitance decreases, right? But charge should be ...
0
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1answer
86 views

How does a minority carrier diffuse?

I have gone through a lot of questions but none of them ask how do the minority carriers approach the depletion layer in the first place. When a p-n junction is formed, negative space charge ...
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0answers
32 views

How can a black hole have a charge? [duplicate]

Under current particle theory, the four fundamental forces use a force-carrying particle. The particle for electromagnetism is the photon. By definition a black hole is a mass from which light can ...
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4answers
1k 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 ...
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3answers
3k views

How much electric charge do electromagnetic waves carry?

Since electromagnetic waves have both electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. How much is ...
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0answers
22 views

Current in discharging capacitor through fixed resistor?

In the textbook I'm using for physics it says that the charge left on the plates of a capacitor after time $t$, that is discharging through a fixed resistor, is $Q=Q_0e^{-t/\tau}$ where $\tau=RC$ is ...
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3answers
1k views

Do quarks violate quantization of charge?

Does existence of various kinds of quarks like up, down, strange, charm, top, bottom violate the quantisation of charge or just redefine it as up quark have charge +2/3 and have -1/3. Or do things get ...
0
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1answer
43 views

Question about particles in electric fields. Homework question

I am currently working on a homework question and I realized that I don't really understand some of the material that we covered so I hoped that you guys can help me clear up some misunderstandings. ...
8
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3answers
2k 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 ...
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1answer
42 views

Typo in physics book (capacitors)

I'm currently working through an AP revision guide. The section on charging a capacitor outlines the following steps: When a capacitor is connected to a battery, a current flows in the circuit until ...
0
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1answer
39 views

Fleming's left hand rule

in Fleming's left hand rule is the direction of current showing the direction of the flow of electrons or the direction of positive charge?
1
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1answer
33 views

Charging a capacitor (terminals)

When a battery is connected to a conductor electrons are repelled from the end of the conductor connected to the negative terminal of the battery and flow to the end of the conductor connected to the ...
0
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2answers
23 views

How does magnetic field affects a charge?

If a electron is placed in a fixed magnetic field, how the electron will get influenced by it? How does magnetic field attacts/repulses the charge?
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2answers
80 views

Conducting rod moving through magnetic field

If a conducting rod moves through a magnetic field which way do its electrons move? In my revision guide it shows the following picture (more or less, but the following is my drawing of it -- I ...
0
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2answers
60 views

How does electron gets negative charge and proton gets positive charge? [duplicate]

I researched much in physics but I still do not know how does electron gets negative charge and proton gets positive charge? What is the source of this charge and energy? How can this particles ...
0
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2answers
762 views

Why doesn't a gaussian surface pass through discrete charges?

I have read that Gaussian surface cannot pass through discrete charges. Why is it so? I have even seen in application of Gauss' Law when we imagine a Gaussian Surface passing through a charge ...
0
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1answer
45 views

When a capacitor finishes charging

When a capacitor is fully charged I usually hear the phrase "the potential difference across the capacitor opposes the battery potential difference, so no more charge flows". What does "the potential ...
0
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0answers
15 views

Integrating Charged Bodies

Why is it possible to integrate charged bodies by first taking a small charge and adding more small charges around it? Wouldn't the similarly charged particles exert an immense amount of force on ...
0
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1answer
96 views

Opacity/Transparency of Conductive Meshes to Charged Particles (Electrons/Ions)

When using a conductive (metal) mesh, effectively a metallic woven fabric, in vacuum applications as a "grid" for charged particle optics, how does one calculate (or at least estimate) the opacity or ...
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1answer
24 views

Why is charge = nALe

Sorry if this question is a bit broad but I can't find any info on this by just searching. The equation q = neAL where L is the length of a conductor, A is the area of cross section, n is the number ...
2
votes
2answers
70 views

How does electromagnetic radiation affect the velocity of a charged particle?

I've heard that the acceleration of a charged particle releases electromagnetic waves. So let's say there is a charged electron moving forwards in a region with a downwards magnetic field. If the ...
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1answer
258 views

Force due to combination of free space and dielectric

I will make a generalized form of my question. There are two point charges $q$, $x$ distance apart. And there is a dielectric slab of thickness $t$ and of dielectric constant $K$. Should the force ...
1
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1answer
40 views

Why do nuclear bomb explosions create an array of visible electric discharges in the form of lightening in the upper atmosphere?

I've seen videos on the internet, showing nuclear bomb test explosions, and there appears to be a large amount of visible lightening discharging numerous times over the development of the mushroom ...
0
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3answers
35 views

Path followed by a free test charge in an electric field region represent the electric lines of forces?

As we know that if we put any free test charge in an electric field which is moving horizontally then it will experience an repulsive force and move in that direction so by that we can say that for ...
1
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1answer
51 views

Classical Hydrogen Atom

I was wondering about the Hamiltonian description of the classical hydrogen atom (two point particles interacting through a Coulumb potential). In particular, I want to know if the fact that ...
1
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1answer
92 views

Does charge of a metal charged by induction determine by which ends of the metal is grounded to?

Does charge of a metal charged by induction determine by which part of the metal is ground to? I draw a diagram to make it simple to understand: Right diagram: When ground is touched with the ...
3
votes
5answers
1k views

Gravity stronger than electromagnetic force in a black hole?

Well, the question has somewhat been answered before, but there's one part missing, which - I'd think - is in conflict with the physical laws. The earlier reply says that the gravitational pull even ...
2
votes
1answer
54 views

Charge conservation in the complex Klein-Gordon Field

This is an extremely naive question (based on a knowledge of chapter 2 of peskin and schroeder) so apologies for any things that seem obvious. The complex scalar field, when quantized, has a conserved ...
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0answers
50 views

Calculating the electric charge of two spheres knowing their potential

I have a system of two spheres, the first one is at a potential of $ V_1 = 1 V $ and the second one is at a potential of $ V_2 = 0 V $ The distance between them is $d$ and the radius are respectively ...