Charge Definition and 1000 Threads

Hi. Inductance and capacitance have many analogies, both conceptually and formally. A capacitor connected to a voltage source carries the charge ##Q=C\cdot V##. The analogous equation for inductance is ##n\cdot \Phi=L\cdot I##. Charge is physical, it's proportional to the number of excess...

Homework Statement Insulator has a 3 cm radius and is a sphere. It has a total charge of -4.2 uC. I need to find the charge density of the insulator. Homework Equations sigma = total charge / volume... I think? The Attempt at a Solution After using the above equation, I got -3.714E-8 C/m I...

Homework Statement Calculate the surface charge density induced by a point source above an infinite conducting plane, with 0 potential. Homework Equations ##E=-\nabla V## ##V=\frac{q}{4\pi \epsilon_0 r}## The Attempt at a Solution I used the method of image charges and I calculated the...

Homework Statement Charge q1= 8.5 nC is located at the coordinate system origin (0,0), while charge q2= -4.46 nC is located at (a,0), where a= 1.5 m. The point P has coordinates (a,b), where b=0.95 m. A third charge q3= 16.5 nC will b added later. It is a 3 part question, first asking for the...

Homework Statement Given the electric potential ##V(r)=A\frac{e^{-\lambda r}}{r}## calculate the charge density ##\rho(r)## and the electric field ##E(r)##. They specify the answer for charge density should be: ##\rho = \epsilon_0 A(4\pi \delta^3(r)-\lambda^2e^{-\lambda r}/r)## Homework...

Hello! I am a bit confused about calculating the induced surface charge density on an infinite conducting plane, with 0 potential, in the presence of a charge, q, a distance d above it. Assuming that the plane is in xy plane and the charge in positive z region, in the book they use the method of...

The momentum-space fermion propagator in the free Dirac theory is given by The arrow on the fermion propagator is said to represent the flow of charge. How can we derive this statement quantitatively from the Dirac Lagrangian? What is the quantitative form of the charge being referred to here?

Homework Statement In the figure, a proton, mass 1.67×10^−27 kg, is projected horizontally midway between two parallel plates that are separated by 0.20cm, with an electrical field with magnitude 7.8×10^5N/C between the plates. If the plates are 5.40cm long, find the minimum speed of the proton...

Homework Statement An electric circuit is shown as above. The switch S is closed for a long time and the current flowing is constant. Given that C1 = 3 μF, C2 = 6 μF, R1 = 4 kΩ, R2 = 7 kΩ If the power at R2 resistor is 2,4 W a) Determine the charge at C1 b) When the switch is opened, after...

Homework Statement Here are the problem statement and the solution. I'm stuck at where the book suggests the formulas for the x and y coordinations (highlighted in yellow) of the third charge. Any explanations or proof on how they came to the conclusion for the third charge coordinations would...

Homework Statement Homework Equations Gauss The Attempt at a Solution I am really confused with question a, I have an idea of how to answer b and c once I obtain an answer for part a... My best guess would be to use Gauss, but I am not sure. Would the field inside be 0? What will the bounds...

Homework Statement The potential difference between the surface of a 2.2 cm -diameter power line and a point 1.9 m distant is 3.8 kV. What is the magnitude of the line charge density on the power line? Express your answer using two significant figures. Homework Equations V =...

Homework Statement The electric field strength just above one face of a copper penny is 2230 N/C. What is the surface charge density on this face of the penny? Homework Equations Electric field of an infinite plane of charge = η/(2*ε0) The Attempt at a Solution I used the above equation, and...

Hi all, this question comes from an old related thread .. https://www.physicsforums.com/threads/help-in-semiconductors-minority-and-majority-carriers.613598/ I'm also interested in the definition of these 'minority charge carriers' in semiconductors. I don't understand the explanations in the...

Chapter 24, Question 61 Given two configurations, ##C_1##, ##C_2## of ##N## point charges each, determine the smallest value of ##N## s.t. ##V_1>V_2##. ##C_1##: ##N## point charges are uniformly distributed on a ring s.t. the distance between adjacent electrons is constant ##C_2##: ##N-1##...

Homework Statement Two 10-cm-diameter metal disks separated by a 0.64-mm-thick piece of Pyrex glass are charged to a potential difference of 1100 V . What is the surface charge density on the disks? What is the surface charge density on the glass? Homework Equations C=(e_0A)/d C=Q/V charge...

Homework Statement A uniformly charged thin ring has radius 13.0 cm and total charge 21.5 nC . An electron is placed on the ring's axis a distance 32.5 cm from the center of the ring and is constrained to stay on the axis of the ring. The electron is then released from rest. Find the speed of...

Homework Statement (a) What is the strength of the electric field at the position indicated by the dot? (b) What is the direction of the electric field at the position indicated by the dot? Specify direction as an angle measured ccw from the positive x-axis. ##Q_{1} = 4.0 C## ##Q_{2} = 9.0...

Homework Statement ##e_{r1}=2## ##e_{r2}=10## ##α_1=\pi /4## ##D_1=100 nC/m^2## ##ρ_s=0## On the borderline of two dielectrics there is no free charge. Calculate the surface bond charge density of both dielectrics. ##ρ_{bs1}=?## ##ρ_{bd2}=?## Homework Equations 3. The Attempt at a Solution...

Homework Statement [/B] ##E_1=6V## ##E_3=5V## ##R_1=150Ω## ##R_2=R_3=100Ω## ##R_4=50Ω## ##R_5=300Ω## ##C_1=1.5 mF## ##C_2=0.5mF## Text: In the first condition when the switches 1 and 2 are open the capacitor 2 has charge on it. First the switch 1 closes and the charge flow of ##q_1=1 mC## is...

I want to solve the Poisson equation for a thin slab of charge held above a grounded plane at z=0. The problem is somewhat reminiscent of the classical image problem of a point charge above an infinite grounded plane but differs because we are using a slab of charge instead which extends above...

1. There's a picture of Electric Field lines going down. Now between these electric field lines (affected by them) are points A and B at differing heights and positions. My question is, how does potential change as you go up/down and left/right? I would like to think that going down means you're...

Homework Statement At our university we were given this problem: charged ball with mass of ##m = 0.0001 kg## and charge ##Q = -10^{-5} C## is placed on geometric axis of thin torus with inner radius of ##r_{inner} = 0.05 m##, outer radius of ##r_{outer} = 0.1 m## and surface charge density...

Homework Statement A metal sphere of radius a is surrounded by a metal shell of inner radius b and outer radius R, as shown in the diagram below. The flux through a spherical Gaussian surface located between a and b is 1.20Q/εo and the flux through a spherical Gaussian surface just outside R is...

Homework Statement The circuit has been completed for several minutes. Suppose that ε = 55 V . Calculate the magnitude of charge on the 100 μF capacitor plate. Homework Equations Q = C * V The Attempt at a Solution Since the capacitors have been fully charged, current has stopped flowing at...

Homework Statement An isolated conductor has a net charge of +14.0 × 10- 6 C and a cavity with a particle of charge q = +4.30 × 10-6 C. What is the charge (a) on the cavity wall and (b) on the outer surface? Homework EquationsThe Attempt at a Solution So I understand that B is just adding the...

Homework Statement Two large metal plates of area 1.1 m^2 face each other, 6.2 cm apart, with equal charge magnitudes but opposite signs. The field magnitude E between them (neglect fringing) is 50 N/C. Find |q|.Homework Equations |q|=σA E=σ/(2Eo)⇒σ=2EoE |q|=2EoEA The Attempt at a Solution I...

Homework Statement Homework Equations E=σ/(2Eo) σ=2Eoma/e a=Δv/Δt The Attempt at a Solution So doing my best to read the velocity over time graph I came up with Δv/Δt=(-2E5m/s)/(10E-12s)=-2E17 m/s/s σ=2Eoma/e =2(8.99E-9C)(9.109E-31kg)(-2E17m/s/s)/(1.6022E-19) =-0.020444 C/m^2 but by the...

Hello, Does anyone have informations about a relativistic origin of the charge-to-mass ratio ?

My question is about the formula ##Q = T_{3} + Y##. Let us say that there is some complex scalar field that transforms as a triplet of ##SU_{L}(2)##; i.e. ##\psi = \begin{pmatrix} \psi_{1}\\ \psi_{2} \\ \psi_{3} \end{pmatrix}## and ##\delta_{2}\psi = i\omega_{2}^{a}t_{a}\psi## with ##t_{1}...

Let's say I have a charge q which is viewed from its rest frame. So it's velocity v is 0. So the so-called magnetic component of its Lorentz force, which is q v x B, is 0. But I can have a magnet moving in this frame of reference. Let's say the velocity of this magnet according to the charge's...

Hello, Is there any evidence that shows a relationship between the angular frequency of the electron in hydrogen, and the charge-to-mass ratio, by the mean of the special relativity ? Looking to reading you

Homework Statement Find the Electric field a distance z above one end of a straight line segment of length L that carries a uniform line charge λ Homework Equations Complicated formula due to lack of font for the notation used by the author of the book. so I wrote it out. I did my best to...

Homework Statement I need to find the tangent of the angle, but I don't think that is the part I'm messing up... Assume the particle doesn't hit the wall. Initial velocity is v. It seems that Vix = 0m/s and ay=0 m/s Homework Equations I thought vfx^2 =vix^2 +2a(xf-xi) f=ma , f=eq The Attempt...

I found it very interesting to see that surface charge and the Poynting vector are being used to describe how a simple DC circuit actually works. Chabay and Sherwood have made an outstanding contribution to physics and engineering in their texts and papers. Of course others jump on the...

Homework Statement A line of charge with a non-uniform charge density lambda=ay, where a=−34.00 nC/m^2 lies along the y axis in the region 0≤y≤2.90 m. Calculate the electric potential of this line of charge at point P on the x axis a distance 0.80 m from the origin. Assume the potential...

Homework Statement The figure is a section of a conducting rod of radius R1 = 1.60 mm and length L = 11.30 m inside a thin-walled coaxial conducting cylindrical shell of radius R2 = 10.5R1 and the (same) length L. The net charge on the rod is Q1 = +3.67 × 10-12 C; that on the shell is Q2 =...

Homework Statement Two point charges are placed on the x axis. The first charge, q1 = 8.00 nC , is placed a distance 16.0 m from the origin along the positive x axis; the second charge, q2 = 6.00 nC , is placed a distance 9.00 m from the origin along the negative x axis. Photo shown by...

Does a charged particle need to experience a momentum changing force to emit light? Or is it sufficient for an observer to accelerate relative to the particle?

Hello, In classical electromagnetism, we learn that an electric charge generates and electric field which other charges can feel through a force. But the source charge does not feel its own generated electric field. In reality, a charge feels its own field. Why are we able to ignore this...

1. Homework Statement An infinite line of charge with linear density λ1 = 6.8 μC/m is positioned along the axis of a thick insulating shell of inner radius a = 2.5 cm and outer radius b = 4.8 cm. The insulating shell is uniformly charged with a volume density of ρ = -667 μC/m3. 1) What is λ2...

Homework Statement A charged nonconducting rod, with a length of 1.33 m and a cross-sectional area of 3.40 cm2, lies along the positive side of an x axis with one end at the origin. The volume charge density ρ is charge per unit volume in coulombs per cubic meter. How many excess electrons...

Field at End of Line of Charge 2 A charged rod of length L=7.10 m lies centered on the x axis as shown. The rod has a charge density which varies according to λ=ax^2 where a=−20.2 μC/m^3 . What is the x component of the electric field at a point on the x-axis a distance of D=3.70 m from the...

Homework Statement Hi, everyone. I have a square and on each vertex of the square is a point charge of "+q". The square has a side length of "r" and these four charges form a system. My problem says to find the work required to assemble the charges shown above, bringing each charge in from...

Homework Statement If the electric field does positive work on a negative charge as the charge undergoes a displacement from point A to point B within an electric field, then the electric potential energy is a) negative b) positive c) increases d) decreases e) electric fields can not do work...

Homework Statement Not so much of homework questions but more to do with clarifying concepts: 1. How do i assess whether or not field lines emitted by charged objects (i.e uniformly charged cube) are both perpendicular to their surfaces uniform? This is in relation to taking the E of ∮φ = EdA...

1. Homework Statement Hi everyone, I am having trouble solving this question. I know that the right answer is d. Homework Equations No equations here, only conceptual stuff. The Attempt at a Solution Say I have the following points: A and B A...

Homework Statement A thin semicircular rod is broken into two halves. The top half has a total charge +Q uniformly distributed along it, and the bottom half has a total charge -Q uniformly distributed along it. A negative test charge is placed at points A, B, and C. *Image attached* Consider...

Homework Statement A thin semicircular rod has a total charge +Q uniformly distributed along it. A negative point charge -Q is placed as shown. (Point C is equidistant from -Q and from all points on the rod.) *Image Attached* Let Ep and Er represent the electric fields at point C due to the...

Homework Statement Homework EquationsThe Attempt at a Solution Current is I = nqvA so drift velocity V is: V = I/nqA Drift velocity for x is: Vx = I/nqA Drift velocity for y is: Vy = 2I/nqA So the ratio of Vx : Vy should be 2:1 since Vy is equal to 2 lots of Vx?? (but correct answer is B)