Charge Definition and 1000 Threads

I mean for the free electron Dirac equation the charge (e or q) does not appear in the equation. It only appears after its interaction with EM field. So it seams the electron does not have the intrinsic property of charge, either that or the EM is integral to the electron. Any idea?

Hi everyone, I was talking to a friend of mine today who's studying electrical engineering and he essentially asked me why a charged particle feels a force when moving through a magnetic field. I thought about it for a moment, and realized I didn't have a good answer for him. Would anyone be...

The example: An electron is trapped in a magnetic field. The electron travels along a circle in a clockwise path. It's my understanding that there is a magnetic field around the electron also circulating in a clockwise direction perpendicular to it's path. Now if this electron was in a...

Homework Statement Initially there is a spherical charge distribution of with a radius ##R_0## and uniform charge density ##ρ_0##. Suppose the distribution expands spherically symmetrically such that its radius at time t is ##R_0 + V t##, where V is the velocity. Assuming the density remain...

S. Weinberg says in his book, "The Quantum Theory of Fields Volume I", that Since electrons carry a charge, we would not like to mix annihilation and creation operators, so we might try to write the field as $$\psi(x)=\sum_{k}u_k (x)e^{-i\omega_k t}a_k$$ where ##u_k (x)e^{-i\omega_k t}## are a...

Homework Statement Homework Equations 3. The Attempt at a Solution [/B] First i found the voltage ##U_{13}=\frac{E(R2+R3)}{R1+R2+R3}=50V## Then i figured that the charge on 1 and 2 is equal since the voltage across is the same right? ##Q1=Q2=U_{13}\frac{C1C2}{C1+C2}=80mC## and...

From what I've learned, excess charge on an insulator stays where it is but excess charge on a conductor spreads uniformly throughout its surface. Why does this happen? Can this be explained in terms of electrostatic potential?

Homework Statement Determine the Work done by the electric field E = axX - ay2y in moving a unit positive charge from position p1 (-2,0,0) to position p2 (5,-1,3) the distances are in m Homework EquationsThe Attempt at a Solution I'm not really experienced with forums therefore my attempted...

could anyone explain me how is it possible to charge your phone wireless, like this video link?

1. A uniform bar has mass 0.0180 kg and is 30.0cm long. It pivots without friction about an axis perpendicular to the bar at point a (as seen in the diagram). The gravitational force on the bar acts in the −y-direction. The bar is in a uniform magnetic field that is directed into the page and...

https://drive.google.com/open?id=0B3IenBvKWb4PZW9rRWg4cXptT2c I had to find the resistance of this circuit between A and B. My teacher said that since the blank wires have zero resistance, the potential difference across the ends of the blank wire is zero(according to v = ir) and thus 1,4 are...

Homework Statement The mass of the ball is 40 milligrams, the applied potential difference is 480 V and the plate separation is 6 centimeters. If the string hangs at an angle of 20 degrees to the vertical, determine the charge on the pith ball. Homework Equations [/B] F=ma E=F/q V=E/d The...

Homework Statement Find the potential of an uncharged metal sphere provided that a point charge q is located at a distance r from its center 2. The attempt at a solution As far as the charges are concerned , some negative charges will build up at the side of the charge because of induction ...

Does the electron field has information about its charge(strength) throughout space and if not why not? I hope this question is not vague.

Firstly I appologize, that I am not native english speaker and I don't study physics(but cybernetics we are getting just some general knowledge about physics), but hopeffuly I will write this right. Homework Statement We know that inside of a conductive object is protected from influence of...

In case of wire(having uniform linear charge density), without assuming the wire infinite long, why we can't take electric field perpendicular to the curved part of the cylindrical Gaussian surface?

Homework Statement Tasks to do: a.)give voltage b.)give the absolute value of charge density for plates Presumably the absolute values of charge densities for plates is equal between the two of them. An electron is accelerated in a homogenic electric field, inbetween two oppositely charged...

Homework Statement an alpha particle with a charge of 2e is fixed at the origin. a proton is aimed at the alpha particle and shot from a distance of 2.00 m at a speed of 3.46x10^6 m/s. How close will the proton come to the alpha particle before coming to a stop? Homework Equations Please help...

Hey all, So the question in Jackson 1.4 is that I have 3 spheres that all have a total charge Q on them, but each sphere has different material properties. For instance, I have a conducting sphere, a sphere with a uniform charge distribution, and one with a charge distribution that has a...

Homework Statement These are two similar questions, one from my previous exam and one from a sample test my teacher provided. I understand how to work the problem, but my question is how is the i or j component decided in each of these?Homework Equations From our formula sheet... The...

Homework Statement An infinite line of charge with charge density λ is parallel to and a distance d above an infinite grounded conducting plate. What is the charge density σ that is induced in the plate? For simplicity, consider the line of charge to lie along the line x = 0. Homework...

Homework Statement [/B] Volume charge density in some space is given by a function ##ρ_v(x)=-ρ_0\frac{x}{a}e^{\frac{-x^2}{a^2}}## where ##ρ_0, a## are positive constants. Determine the electric field vector in arbitrarily chosen point in space. Homework Equations 3. The Attempt at a Solution...

The following article says virtual particles don't exist or are just book keeping device. https://www.physicsforums.com/insights/physics-virtual-particles If that's the case, then how do you explain charge screening? We observe the charge of an electron to be less than the bare charge, or what...

Hi. Is the resistance of a charged cable different compared to a cable with zero net charge? If it is charged negatively, one could argue that now there are more carriers for the current, so the resistance should be smaller (similarly to water that becomes more conductive if ions are added). On...

Homework Statement A very thin plane of length ##2a## is placed in the air at height ##a## above the conducting surface. The plane is charged on its surface and the expression for it's surface charge density (##ρ_s##) is given by ##ρ_s=ρ_{s0}*\frac{x}{a}## and ##ρ_{s0}## is some constant. a)...

How much charge is actually transferred when two insulators are rubbed together? Example: When glass rod and wool are rubbed together

I'm trying to understand (well, maybe in an oversimplified way) what permanent changes, if any, would be experienced by a positive electrostatically charged plate used to accelerate a free electron in a vacuum, but where the electron would not strike the plate. I assume there would be some...

Homework Statement A ball of mass m is attached to a rope of length L which has one end at the origin; the ball moves in a horizontal circle at constant speed v0 on a frictionless plane; the velocity is always at 90◦ to the rope. The ball has a charge q, and moves in a constant magnetic field...

Homework Statement Hi everybody! I'm very stuck trying to solve this problem, hopefully some of you can give me a clue about in which direction I should go: Determine the multipole expansion in two dimensions of the potential of a localized charge distribution ##\lambda(\vec{x})## until the...

Hi I am confused about an example in my textbook related to charge stored by a capacitor A 100 uF capacitor and a 700 uF capacitor are placed in series, along with a cell of 3V. Calculate the p.d. across the 100 uF capacitor. The book states the solution as follows: "Using the reciprocal...

This is my first time using this site so please excuse me if I missed any guidelines. 1. Homework Statement A plastic rod having a uniformly distributed charge Q=-25.6pC has been bent into a circular arc of radius R=3.71cm and central angle ∅=120°. With V=0 at infinity, what is the electric...

I am working on "electrical energy" storage and I want to know why exactly can't we store "electricity" from a power plant. My understanding is that "electrical energy" storage actually refers to the conversion of electricity to other forms of potential energy (such as mechanical eg: dam, or...

1. Homework Statement : Homework Equations :[/B] A conductor is an equipotential surface. The charge density near a conductor is proportional to the electric field. Electric field is the negative gradient of potential and thus electric field is in a direction normal to the surface.The Attempt...

Homework Statement Around a point charge there are three points: A, B and C. Determine the electric field vector for those points. Also, determine the force vector for q0 if it was in point B. Q = 10 µC, a = 1 m, b = sqrt(3) m, q0 = 10 pC 2. The attempt at a solution Here is the attempt at a...

Homework Statement Lets say you have a infinitely long surface with one side of length ##L## and a surface charge density ##ρ_s## and you need to transform that into a linear charge density ##Q'## so that you can represent the surface along some axis ##y## so the the surface is placed normal to...

1. Homework Statement A fixed parallel plate capacitor is charged. A point charge is starting to move with an initial speed 1.0 m/s at shown initial position. The capacitance is 5.0 F. The mass of the point charge is 0.80 kg. Assume that the plate length is infinite. No gravity. The initial...

Hello guy, I have questions with the use of the terms "net charge" As far as I know we use net charge when we want to make a sum of positive charge + negative charge For example the net charge of Na+ = +11+(-10)= +1 the net charge of Cl- = _______ = -1 But can we use...

Where do the charge comes in electron-positron pair production

Homework Statement A thin infinite wire with linear charge density λ is located parallel to an infinite conducting surface, which is coincident with the x-y plane (i.e., z = 0). The wire is parallel to the ˆx direction and is located a distance z = d from the conducting surface. The figure on...

Homework Statement A sphere of radius ##a## is non-uniformly charged on its surface with a charge whose surface density is ##ρ_s(φ)=ρ_{so}(cosφ)^2## where ##φ## is the angle measures from the z axis, (0≤φ≤π) and ##ρ_{s0}## is a constant. Determine the expression for the total charge distributed...

Hi. I'd like to show that a conducting, charged spherical shell can shield the field of an inside opposite point charge even if this charge is not at the center. I was thinking about a Gaussian surface just outside the sphere, such that if there were electric field vectors they would be...

Homework Statement Describe and account for two constructional differences between a moving-coil galvanometer used to measure current and the ballistic form of the instrument. An electromagnet has plane-parallel pole faces. Give details of an experiment, using search coil and ballistic...

Homework Statement . With this problem, how should I set image charges so as to satisfy the same boundary condition? And if possible, could you let me know how can that image charge configuration be deduced? Thanks for reading. Homework EquationsThe Attempt at a Solution Well, I first put...

hi, i want to know that how many techniques are being used for charge separation? and which one is more effective for solar cell? can you give some idea about it that which one is better and how to make better power conversion efficiency. after going thoroughly through literature review i am...

Homework Statement What are the electric and magnetic fields due to a charge that is moving with uniform acceleration? (Non relativistic) Homework Equations Retarded solutions for the vector and scalar potentials. The Attempt at a Solution My attempt might be an overkill because I'm using the...

Homework Statement "An infnitely long hollow cylinder of radius ##a## has surface charge density ##σ_a##. It is surrounded by a coaxial hollow cylinder of radius ##b## with charge density ##σ_b##. The charge densities are such that the total confguration is electrically neutral. Using whatever...

I am trying to measure the charge(or voltage) of a positively charged sphere by touching it with a non- calibrated electroscope. I am getting consistent results in the separation(or angle) between the metal leaves, but I don´t know how to calculate the voltage between the leaves from there. I...

Howdy y'all! If you could help with the following question, my physics class and I would be extremely grateful. A charged oil droplet is suspended motionless between two parallel plates (d=0.01m) that are held at a potential difference V. Periodically, the charge on the droplet changes as in...

Homework Statement I don't exactly conceptually understand what the potential is. The electric field is a vector at a given point from the charge that describes the strenght and the direction of the fields. Potential is given as a potential of a point in referenve to another point in spave? I...

Hi. If an electrically neutral, conducting rod is brought close to a (say negatively) charged object with one end, charges will separate due to electrostatic induction roughly as follows: Let's now connect the rod to the (far-away) ground with a long cable. Does it make a difference whether...