Charge Definition and 1000 Threads

What equation in QM show us that symmetry in quantum-mechanical phase implies charge conservation?

Homework Statement You dope an $n$-type substrate at time ##t=0## with electrons and holes around the points: ##\vec{r}_{0,c}## and ##\vec{r}_{0,v}## respectively. The initial densities' distributions are: $$\Delta n (\vec{r},t=0) = \frac{\Delta N_0}{(2\pi...

Is there anyway to detect the Earth's magnetic field without a compass? or putting it differently, Is there anyway to detect an electric field without bringing a charged particle in proximity of the field?

The circuit is intended to control the charging of a 12v 7ah battery by a 10w, 24v volt solar panel.

Homework Statement Hi guys, I hope you can help me with this problem, because I do not have any idea and I could not find anything that could help me, thank you in advance! Draw the electric field lines due to a punctual charge Q immersed in a dielectric medium with constant K1. Q is separated...

Homework Statement I'm having a bit of trouble with this problem: "A spherical ball of charge has radius R and total charge Q. The electric field strength inside the ball (r≤R) is E(r)=r^4Emax/R^4. a. What is Emax in terms of Q and R? b. Find an expression for the volume charge density ρ(r)...

The question asks to find total charge in a region given x has lower bound 0 - upper bound 5 , y has lower bound as 2 and upper bound as 5. Based on knowledge I have been reading throughout the chapter, I set up a double integration with those dxdy, but the results went out to be off - compared...

Take the following diagram of 4 1.5V batteries connected in series to creat and net voltage of 6V (the numbers are of no significance here). If we were to short circuit the system by connecting battery 1 to battery 4 (or run the current through a load), wouldn't there be electrons traveling...

I wonder, what would happen if you started dropping lots of electrons into an existing black hole which otherwise doesn't accrete any new matter? The charge of the black hole would build up much faster than the mass. Wouldn't its charge become so high at one point that further electrons would...

Homework Statement What collection of image charges solves the problem in above pictured ?? Homework EquationsThe Attempt at a Solution One of the image charge should be in dielectric region q'=-((e2-e1)/(e2+e1))

I have a moving charge in a generic motion, and I pick a point p, how do I get the electric field caused by the charge on point p, at any time? Can I use the coulomb definition of electric field that relates it's strenght with the Distance? Or does that law works only when the charge is static...

Homework Statement The current in a wire varies with time according to the equation I(t) = 6.00 A + (4.80 A/s)t, where t is in seconds. How many coulombs of charge pass a cross section of the wire in the time period between t = 0.00 s and 3.00 s Homework Equations I=dq/dt The Attempt at a...

Homework Statement I am trying to derive an expression for the potential of a positive point charge by bringing in another positive test charge in from infinity to a point at a distance R from the point charge. Homework Equations $$V_f - V_i = - \int \vec E \cdot d \vec r \, dr$$ The Attempt...

The intrinsic charge parity of a species is the ##\eta_C## defined in the equation $$\mathcal C |\psi \rangle = \eta_C |\psi \rangle $$ which can take on values ##\pm 1##. Since the gluon carries a colour charge, it is not an eigenstate of the C (charge conjugation) operator. 1) Why do I...

I need a charged particle trajectory in crossed E and B that is a cycloid in the x-y plane. This part is simple enough, but I want the trajectory to be parabolic in the x-z plane. The images will help explain what I need. The left image shows the shape I want to achieve, and the right image...

Homework Statement Given an electric field $$\vec E(x,y,z)=\begin{pmatrix}ax^2+bz\\cy\\bx\end{pmatrix},$$with nonzero constants ##a,b,c##, I am supposed to find the charge density ##\rho(x,y,z)## which is necessary to create this field ##\vec E##. Homework Equations ##\rho=\frac{\mathrm...

From what I understand, there are 2 sets of fermions, one left-chiral and one right-chiral. Every electron in my body can be left-handed or right-handed. Do they stay the same forever or can they change chirality? Or is it more abstract property and a single electron can not be assigned...

Homework Statement Homework EquationsThe Attempt at a Solution I don't understand how it looks like, how to approach this problem. I think it's maybe image charge or Laplace equation

Homework Statement Homework Equations / 3. The Attempt at a Solution [/B] Here is what I attempted for the HW. I only got 2/10 for this here so I'm wanting to correct my mistakes.

1. Find the magnitude and direction of the force experienced by the charge of 3microcoulombs.Homework Equations After subtending forces of both the particles on the third one, we need to find the aggregate magnitude of the charge experienced by it. The Attempt at a Solution I was able to find...

Homework Statement From the textbook: Homework Equations / 3. The Attempt at a Solution My attempt at the solution: looking to fix my issues and help correcting my work.[/B]

In Berkeley Physics Course (Volume II) on Electricity and Magnetism: https://www.scribd.com/doc/128728926/Electricity-and-Magnetism-Berkeley-Physics-Course-Purcell ...Purcell discusses the invariance of charge (Section 5.4), the electric field measured in different frames of reference (Section...

There are two charges with charge q and mass m and they are in equilibrium. Then, in the diagram why is my teacher saying that electrostatic force(F)=mg? Below is diagram.

Homework Statement : STATEMENT:[/B]A point charge at rest is released in an electric field. It will move along the electric field line...(1) REASON: The force on a point charge is along the field line...(2) State whether: A) 2 is the correct reason for(1) B) Both (1) and (2) are correct but 2 is...

I'm working on a finite element simulation of the electrostatic potential V(r) in and around semiconductor nanowires, based on solving Poisson's equation. While the details of the problem will follow shortly, the crux of where I run into trouble is that for nanowires it is important to include...

Homework Statement Four particles with equal charges q and equal masses m are placed on a plane so that they form the corners of a square with side length a. The charges are then released from rest at this configuration (shown as (i) in the figure). After the release, the particles accelerate...

Homework Statement Homework EquationsThe Attempt at a Solution I don't understand what is the meaning of "potential of cylinder relative to the plane" I think the potential of cylinder is just -q/2πε ln r by Gauss's theorem[/B]

Which property of compounds, organic ones in particular, can help us predict their charge(s) at a specific pH? Is pKa/pKb the only one? I would like some confirmation on this. Thank you very much!

Homework Statement In an abrupt p-n junction we consider the junction between one side p-doped with ##N_A## acceptor atoms and another side n-doped with ##N_D## donor atoms. Initially the chemical potential is different in the two sides, but thermal equilibrium requires that the chemical...

A few dozen years ago the endings of lightning rods were sharp. I read somewhere that it served one purpose - it enabled the flow of charge between the ground and the cloud, thus reducing the voltage and lessening the probability of another lightning. What I don't understand is why this sharp...

I need help trying to set up this problem. I want to find the capacitance between a point charge and a finite plate (or disk) as the point moves from above the center of the plate to some distance off the plate. I have been able to simulate this problem using FEM, however, there should be a...

Years ago I read an article illustrating the vastly different strengths of the electromagnetic and gravitational forces. The article gave a figure for the number of excess electrons dispersed throughout the Earth that it would require to overcome the gravitational binding of Earth's matter and...

Homework Statement Use Gauss's law to find the electric field caused by a thin, flat, infinite sheet with a uniform positive surface charge density σ. Homework Equations φ(flux) = ∫E*dA = qencl / ε0 The Attempt at a Solution I set up a diagram like this...

Homework Statement A metallic sphere of radius a is placed concentrically with a metallic spherical shell with inner radius b and outer radius c. The sphere has a total charge of 2Q and the shell has a total charge of 3Q. (a) What is the charge distribution? Specifically, what is...

Homework Statement Theres a cylinder rod inner radius a outer raidus b.we want to find electric field between a and b,like point r (or radius r) a<r<b. Homework Equations Gauss Law The Attempt at a Solution [/B]I am trying to find Q enclosed but something make me confused.I am...

I need a flux of highly positive ions, at least penta-valent ions (5+ or more, 6+, 7+, ...); there are ion sources that can generate a proton flux, but I need 5+ ions; do you know how I can do that?

Homework Statement http://imgur.com/a/TOUjV part b, specifically finding the maximum charge for C1. The question that boggles me is whether Imax changes on the left side of the circuit, after the switch closes. Homework Equations V=IR Xc = 1/(wC) XL = wL The Attempt at a Solution I was able...

Hello, I am trying to solve an issue which occurs when two robots with different static charges make contact. It has been some time since my Physics classes and I have some ideas that are only partly making sense to me. I need to minimize the effect that a static shock is having on a small...

Homework Statement a) Common transparent tape becomes charged when pulled from a dispenser. If one piece is placed above another, the repulsive force can be great enough to support the top piece’s weight. Assuming equal point charges (only an approximation), calculate the magnitude of the...

I'm working on this: When I consider a disc with radius ##a## and total charge ##Q## uniformly distributed (placed in the XY plane and centered at the origin) and determine the volume charge density in cylindrical coordinates, I have assumed is of the form ##\rho=A \delta (z) U(R-r)##, (##U## is...

Homework Statement 2 large plates are separated by a distance d and a space charge of uniform charge density p is placed between them and a potential difference V is applied across the plates. Find the electric field stength at a distance x fromt the positive plate The answer is -V/d...

Homework Statement Below are a few equations listed in my text for use in calculating capacitance in dielectrics. I'm wondering which of these are applicable in specific scenarios Homework Equations 1. k = C/C0 - with C0 indicating capacitance w/o dielectric 2. v = v0/k 3. E = E0/k 4. σi = σ(1...

Question: If you charge a capacitor circuit and then separate the capacitor, does voltage increase beyond the initial source? It seams counter intuitive that if you plug a 9 Volt battery into two metal plates and pull the plates apart that you'll get massive voltage spikes, but that's what the...

Homework Statement A small sphere with mass 5.00×10−7 kg and charge +6.00 μC is released from rest a distance of 0.400 m above a large horizontal insulating sheet of charge that has uniform surface charge density σ = +8.00 pC/m2.Using energy methods, calculate the speed of the sphere when it is...

Homework Statement My questions are just related to part a of this problem. Homework EquationsThe Attempt at a Solution I know that potential inside a conductor is equivalent to potential on the surface of the conductor and potential at any point is an algebraic sum of potential...

I have a question about definition of charge neutral point. I`m reading some article about trilayer graphene, and this term, charge neutral point, is used in the article. I googling this word, but I can`t find something which can tell me what it is. In monolayer graphene, what i found by...

I have been using Maple for sometime as its document interface feels nicer and more friendly than mathematica's . I have never been able to plot arrows in Mathematica or use indices efficiently. I am more of a curious self teaching physics person. But I just found something interesting when...

Homework Statement We have an electric dipole with moment P=2*[10][/-5] pointing in x direction. What is the force experieced by dipole at origin when a point charge Q=3*[10][/-4] is located at (0.014 m ,0,0) Homework Equations 1. [E][/dipole]=(1/4π[ε][/0])(2p/r3) 2. p=qs 3. F=qE 4. τ=pEsinϑ...

Homework Statement Homework EquationsThe Attempt at a Solution I have the full solution, the first part being: I don't understand how they came up with the expression for Vab. I know usually ΔV=-∫E dl, but I'm not sure how they found their expression. Can someone explain? Thanks.

Homework Statement One type of ink-jet printer, called an electrostatic ink-jet printer, forms the letters by using deflecting electrodes to steer charged ink drops up and down vertically as the ink jet sweeps horizontally across the page. The ink jet forms 29.0 μm diameter drops of ink...