Electric field Definition and 1000 Threads

Homework Statement A point charge +q is placed outside a grounded conducting sphere of radius a. which of the following is ##not## true. a) There is an attractive force between the sphere and the charge b) The induced surface charge density on the sphere is not same everywhere c) The electric...

While reading the book, Electricity and magnetism, the author says that electric field just outside a spherical shell is ##4\pi \sigma##, on it ##4\pi\sigma r_0^2## ,inside is ##0## and outside is ##Q/R^2##. My derivations :- For inside, ##E\Delta S = 4\pi Q = 0## since ##Q = 0##. For...

In class we were trying to calculate the induced electric field created by changing the magnetic field stregth. Imagine there's a circular surface which magnetic field out of the screen.Since we are changing the magnetic field from Faraday's Law there should be a induced current or charge flow...

We know that there exists no electric field inside a conductor. But while calculating drift velocity of electrons inside an electric conductor, why do we consider the electrons are present inside the charged conductor?

Homework Statement Two positive point charges, A and B are 6m apart. The electric field intensity at point C, midway between the two charges is 5 N/C directed towards B and the potential at the same point is 45V. Find the magnitude of A and the magnitude of B. Homework Equations E = kQ/r2 The...

I've got confused over a topic in my physics textbook (Fundamentals of Physics). The textbook says if a charged particle is enclosed by a shell of uniform charge, there is no electrostatic force on the particle from the shell. I don't firmly get this, as the book uses a confusing reasoning for...

Why the gaussian surface is "A" instead of "2A" on the right-hand side?(the photo attached below) Due to the thickness of the sheet? I usually find that E=σ/2ϵ0 is being frequently used but we hardly use E=σ/ϵ0. When can I directly apply the equation E=σ/ϵ0 ?

Hello, An electron accelerated through a pd of V volts will have a K.E = eV. Why isn't the K.E less than this considering that some of the work done by the field has been radiated as electromagnetic waves by the accelerating electron ? All insights very welcome.

Homework Statement An infinite metal plate has a surface density of charge σL=-6μC/m² , Left side and a surface density Of load σR=+4μC/m² , in the right side. A Gaussian surface In the form of a circular cylinder, with area A 12 cm², is Located with the left side inside the plaque and a thin...

Homework Statement which of the following proposed space-time dependent electric fields in vacuum is/are allowed by the equations of EM theory? a) $$E_x=E_1\sin(kz-wt),E_y=E_2\sin(kz-wt),E_z=0$$ b) $$E_x=E_1\sin(kz-wt),E_y=2E_1\cos(kz-wt),E_z=0$$ c)...

refer only to the image above, not the question 4.) Two point charges, Q1 and Q2, are placed 0.30 m apart on the x–axis (shown in the figure above) Charge Q1 has a value of –2.50 x 10–6C. The net electric field at point P is zero. a. What is the sign of charge Q2? ____ Positive ____...

Homework Statement I am working on annotating the pre-lab for this Electric Field lab and needs to have some help look at my work. The second question of the Pre-Lab is comparing the answers between two persons Kate and Victor. Based ib this diagram below * o (-1) * * o (+1)...

Homework Statement Two thin glass rods are placed side by side 4.70 cm apart as shown in the diagram below. They are each 11.3 cm long and are uniformly charged to +10.4 nC . Answer the questions below regarding the electric field along a line which is drawn through the middle of the two glass...

Homework Statement A hemispherical shell has radius ##R## and uniform charge density ##\sigma##. FInd the electric field at a point on the symmetry axis, at position ##z## relative to the center, for any ##z## value from ##-\infty## to ##\infty##. The Attempt at a Solution Let ##\theta## be...

Homework Statement I was wondering in what situation would the potential and the electric field of the system both be equal to zero at the same time? Homework Equations W=-ΔU=-ΔVq ΔV=-∫Edr V=kQ/r (with reference r->∞) The Attempt at a Solution I know for the middle of a dipole the potential...

Homework Statement (Taken from Serway and Jewett Chapter 23, Q44, 9th Edition) A thin rod of length ## l ## and uniform charge per unit length ##λ## lies along the x-axis as shown in the image attached. (a) Show that the electric field at P, a distance d from the rod along its perpendicular...

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...

I understand that if electric field at any point is 0, it implies that potential is constant not necessarily 0. But what if the potential at a point is 0? Does it imply that electric field is 0? Me and my friend had an argument and I am in the favour of electric field not being 0. Do I win guys...

Hello all, i am having a hard time with EM, specially with the most simple concepts that i don't seem to grasp at all and the simple exercises that should be quite simple to solve. So the question is. ( i will omit the constant (1/4pieo) for practice sake When i calculate the eletric field...

I would like to know why electric field of EM waves changes it's direction to opposite when hitting a conductor surface. I know that electric field inside a conductor is zero but I am not able to connect these two situations.

[ Moderator note- Edited to re-insert formatting template headers] Hi guys, I am stuck at this problem, Homework Statement Here it is given that an insulating sphere of radius a, carries a charge density ρ=ρ'( a^2-r^2)cosθ, when r <a. How will the leading order term for the electric field at...

I came upon this: http://physics.stackexchange.com/questions/174514/will-the-electrostatic-force-between-two-charges-change-if-we-place-a-metal-plat/323006#323006 question on Physics Stackexchange which I found very interesting. The configuration is basically two positive point charges q and...

Homework Statement I am modelling a ray-tracing algorithm(image method), and I am in the part where I am getting the summation of all EM "rays" hitting the receiver. I come to a problem where I can't properly convert and unsure to do so. Ideally, I should have a collection of Ei waves defined...

I read on physics.stackexchange that using Gauss Law we can prove that the electric field strength increases as the radius increases inside a metallic conductor. Later on the same website, I encountered a contradicting statement that claimed that inside a conductor, the charges aren't free to...

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...

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

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...

Homework Statement The region is a circle with radius=a Homework Equations Using Faraday's law to find E. The Attempt at a Solution Dealing with the Left side of the second equation first 1.) Pull out the Partial/partial t because it is a constant in this equation 2.) Now I have B dot...

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...

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 I have a potential Value like ##V=V(x,y,z)+C## I found ##\vec E## using partial derivative, like ##\vec E=((-∂V/∂x)i+(-∂V/∂y)j+(-∂V/∂z) k)## Theres two position vectors, ##\vec r_{a}=2i## ##\vec r_{b}=j+k## We need to find ##V_{ba}=?## Homework Equations...

I was reading a book on Electromagnetism and it's said on deriving the electric field that $$\nabla \frac{1}{|x-x'|} = - \frac{x-x'}{|x-x'|^3}$$ where ##|x-x'|## is the magnitude of the distance between two point charges. I've tried to derive this result and I found that $$\nabla |x-x'| =...

Hi All, what is the reason why very close to an electromagnetic source (Fresnel Region), the wave impedance Z0 in free space for electric field and magnetic field is not the same? Z0 for magnetic field increases and for electric field decreases by increasing the distance from the source...

What I want to discuss here is what happens to the thermal velocity when an ionised gas molecule has been put into an electric field. Due to the charge (e) and potential difference (V), how much velocity has been gained by the ion can be calculated easily.eV = ½mv2 Where e is the charge of the...

I'm having some confusion about the creation of magnetic field lines. How I understand it so far, is that a magnetic field is basically an electric field viewed from a relative point. I don't have a great understanding so far, as I just started to learn about it, but I've learned that objects...

Homework Statement Electric Dipole makes small oscillation is electric field find its ##ω## Homework Equations ##τ=pEsinθ## ##τ=I∝## The Attempt at a Solution ##τ=pEsinθ## ##τ=I∝## so ##pEsinθ=I∝## which that's...

According to responses at: http://physics.stackexchange.com/questions/93390/field-of-moving-charge-lorentzlienard-wiechert The Lorentz contraction of the electric field of a charge with uniform velocity is supposed to be symmetric across the plane pi/2 radians from the velocity vector of the...

So I know that EM waves travel perpendicular to the electric and magnetic fields which are also perpendicular to each other. What I'm having difficulty understanding is since light is an EM wave and can travel through the vacuum of space, does that imply that everywhere in the universe there is...

Homework Statement Uniform Slab: Consider an infinite slab of charge with thickness 2a. We choose the origin inside the slab at an equal distance from both faces (so that the faces of the slab are at z = +a and z = −a). The charge density ρ inside the slab is uniform (i.e., ρ =const). Consider a...

I've read that in an electric field due to it being a vector if its mirrored symmetrically the components cancel out. However, the electric potential is a scalar so the components are added not canceled out. This is consistent with one question in my physics H.W., but not for another question...

So according to classical electrodynamics, an electron would produce an electric field that is a physical entity in and of itself. This field has momentum so when a test charge is placed within this vicinity, it would be affected by the field itself, not the electron. But what about the QFT way...

Homework Statement A spaceship encounters a single plane of charged particles, with the charge per unit area equal to σ. The electric field a short distance above the plane has magnitude _____ and is directed _____ to the plane. a) σ/2∈0, parallel b) σ/2∈0, perpendicular c) σ/∈0, parallel...

I think I have this correct, could someone please verify? I compared answers with a friend who got 2.0 x 106 N/C to the left, and I can't figure out how they got that answer, so I'm hoping mine is right... 1. Homework Statement A negative charge of 3.5 × 10–8 C experiences a force of 0.070 N...

I'm doing some special relativity exercises. I have to find $$x(t), v(t)$$ of a charged particle left at rest in $t=0$ in an external constant uniform electric field $$\vec{E}=E_{0} \hat{i}$$, then with that velocity I should find the Liénard–Wiechert radiated power. I will show you what I did...

I have a good understanding on the hall effect. However, I was told by my tutor that the electric field direction at equilibrium remains pointing in the negative side of the conducting material and the force it generated is canceled out. But further reading online text, the electric field...

Homework Statement An electric dipole with magnitude ##p = 0.2Cm## is placed inside a uniform electric field of ##\vec{E} = 100\vec{i} + 70\vec{j} + 40\vec{k} \frac {N} {C}##. The dipole was initially pointing along the +x direction. You then start to rotate it first on xz-plane towards...

Homework Statement a thick spherical shell carries charge density k/r^2 a<r<b find E in the three regions r<a a<r<b b<r Homework Equations E dot da = Q/ε The Attempt at a Solution I can't understand why, when integrating, they choose for ii to integrate between a and r, iii and the between a...

Homework Statement so when I do a point charge and a line charge, it is just the charge over the hypotenuse squared times cos(theta) but suddenly when I get to a surface charge, I have to add the equation for the surface into the equation. Obviously, I have to integrate over the surface, but...

Homework Statement Theres a rod and has ##a## length ##L## and we want to calculaate the electric field far from rod like ##L<<a## Homework EquationsThe Attempt at a Solution I found the equation for a normal case and it was ##\frac{1}{4\pi...

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...