Charge Definition and 1000 Threads

  1. A

    Why is there confusion about capacitors and potential difference between plates?

    So I understand that a capacitor consists of 2 plates separated by a distance which creates a potential difference between the plates. But I was confused, when watching this physics video it seemed to be saying that once the capacitor was fully charged, the plate closest to the positive terminal...
  2. M

    Magnetic Field due to Opposing Coils

    Homework Statement Describe the magnetic field you would observe if two coils were connected with magnetic fields pointing in opposite directions. Homework Equations No equation The Attempt at a Solution If the magnetic field was pointing in opposite directions, would it mean that it would...
  3. W

    Electrostatics: Energy from a charge distribution

    Homework Statement [/B] For a straight wire of length 2L carrying a uniform charge density ##\lambda##, find 1) potential a distance z above the centre 2) electric field E at that point, 3) energy of this charge distribution Homework EquationsThe Attempt at a Solution 1) and 2) I can do...
  4. brioches

    A positive charge of magnitude Q1 = 8.5 nC is located....

    Homework Statement A positive charge of magnitude Q1 = 8.5 nC is located at the origin. A negative charge Q2 = -8.5 nC is located on the positive x-axis at x = 16.5 cm from the origin. The point P is located y = 7.5 cm above charge Q2. Calculate the x-component of the electric field at point P...
  5. P

    Calculating the surface charge of a sphere and a conducting shell

    Homework Statement (Problem 2.38 From Griffth's Electrodynamics): A metal sphere of radius R, carrying charge q, is surrounded by a thick concentric metal shell (inner radius a, outer radius b). The shell carries no net charge. Find the surface charge density ##\sigma## at R, a, and b...
  6. Fara_k2

    How to find the charge on each capacitor

    Homework Statement Two batteries are connected to two identical capacitors X and Y.Initially all the plates of the capacitors are uncharged.How to find charge on each Capacitor in the given diagram.Let the Capacitance of Capacitor be C. Homework Equations 1.Q=CV 2.Kirchoff's law 3.C=C1+C2 (...
  7. H

    Does the charge of a capacitor change during immersion?

    If given a capacitor with stored charge, would its charge remain constant before and after it is immersed in a liquid (i.e. distilled water)? Why? I know that before immersion, the capacitance would be = (ɛAV/d), but would that be the same if immerged in distilled water?
  8. Bonewheel

    Sphere with non-uniform charge density

    Homework Statement A sphere of radius R carries charge Q. The distribution of the charge inside the sphere, however, is not homogeneous, but decreasing with the distance r from the center, so that ρ(r) = k/r. 1. Find k for given R and Q. 2. Using Gauss’s Law (differential or integral form)...
  9. KoontzyN

    Total interior and exterior charge of a hollow sphere?

    Homework Statement A hollow conducting sphere has inner radius R and outer radius 1.5R. A +40nC point charge is placed at the center. What is the total charge on the interior and exterior walls of the sphere? R=10cm Homework Equations Gauss's Law σ = Qenc/A The Attempt at a Solution I'm not...
  10. L

    Calculate a charge distribution given an electric potential.

    Homework Statement Find the distribution of charge giving rise to an electric field whose potential is $$\Phi (x,y) = 2~tan^{-1}(\frac{1+x}{y}) + 2~tan^{-1}(\frac{1-x}{y})$$where x and y are Cartesian coordinates. Such a distribution is called a two-dimensional one since it does not depend on...
  11. lightest

    Point charge with grounded conducting planes angled 120

    Homework Statement The problem states: "A point charge q is located at a fixed point P on the internal angle bisector of a 120 degree dihedral angle between two grounded conducting planes. Find the electric potential along the bisector." Homework Equations ΔV = 0 with Dirichlet boundary...
  12. BillTre

    DNA Based, Charge Controlled, Nano-Scale Arm

    This Science magazine news article describes a nano-scale arm made of DNA whose postion is controlled by charge. There is a little movie too.
  13. J

    What is the Charge Density in the Region 0<z<1 Using Gauss's Law?

    Homework Statement Homework EquationsThe Attempt at a Solution In the region |z|<1 , E(z) = -dV/dz = 10zk This means there is a variable electric field in the region -1<z<1 .In the +z region it is directed in the +z direction and vica versa . For finding the charge density in the region...
  14. T

    How can each Coulomb of charge transfer energy

    regards my question is how each coulomb of charge can lose (transfer ) energy when going from a to b when electrons are very slow the definition of potential difference: is how much each coulomb of the charge loses (transfer ) energy when going from a to b an example to clarify the question...
  15. sumit_1

    Understanding Charge Flow in RC Circuits: A Scientist's Perspective

    I have a RC circuit which also includes a battery, the capacitor has some charge initially before we put all the components in the circuit. Now as I connect all of them then charge will start to flow, but wheather this charge will be the sum of initial charge on the capacitor and the new charge...
  16. G Cooke

    Conservation of electrical energy on a conductor

    I'm having trouble seeing how electric potential energy production on a conductor follows conservation of energy. Let's use the photoelectric effect as an example. A photon with energy E = hν strikes a conductor, ejecting a photoelectron with a maximum kinetic energy of hν - φ. Assuming the...
  17. Hiero

    Attempt to find the magnetic field of a moving charge

    First let me say THANK YOU to anyone who reads my work and tries to help, I know it can be a pain to decipher the work of others (although I've tried to make it as clear as possible). If any part is unclear I will try to explain it. I cannot for the life of me see any flaws in the argument...
  18. Hiero

    Magnetic field of a moving charge and coulombs force

    By relativity+coulombs force, I worked out that the (magnitude of the) magnetic field of a charge Q moving at speed V should be (ϒVV/c2)Q/(4πε0r2) or in terms of mu, ϒVμ0VQ/(4πr2) (where the distance r is measured normal to V). When I google the answer I only find the same thing but without the...
  19. I

    Why center of mass? Why not center of charge?

    Hi, In electrostatics, we have Coulomb's law for the electric field of a point charge. We can generalize to the electric field of a continuous charge distribution, using $$E=k\int r^{-2}dq.$$ It would seem, using the same argument that gets us to the previous equation, we could define the...
  20. Altair Tans

    Exploring a Universe with One Point Charge

    What if there is a universe with just one point charge in existence....just a charge with vast emptiness around it....now here all laws of physics remain same... But is the concept of field and energy defined there??
  21. Jason Louison

    Automotive Air Mass into Cylinder (Intake Charge)

    Hello Physics Forum Community! It sure has been a while! :) I have been hard at work on my goal; to create a spreadsheet that simulates the Internal Combustion Engine (Spark Ignition). I can't take all the credit for having come this far, so there will be links to a few sources below that I have...
  22. S

    Charge different entering and leaving a resistor

    Homework Statement Is a charge different upon its exit versus its entry into the lightbulb? Homework Equations PE = Vq The Attempt at a Solution Well, the answer is that the charge stays the same. Based on the equation above, since energy certainly gets reduced V must drop but I don't...
  23. B

    B What is source of fundamental particle charge?

    Hello, Analogous to mass of fundamental (not composite) particles coming from interaction of those particles with the Higg's Field, does charge of fundamental particles come from interaction of those particles with some known/hypothesized fundamental field? Thank you!
  24. S

    Potential difference in between positive and negative charge

    Homework Statement Two point charges Q1= +5.00 nC and Q2 = -3.00 nC are separated by 35.0cm. What is the electric potential at a point midway between the charges? Homework Equations V = Ke(q/r), PE = Vq[/B] The Attempt at a Solution This question is from Serway textbook. The answer is...
  25. Marcus95

    Finding Total Charge from E-field

    Homework Statement A static charge distribution has a radial electric field of magnitude ##E = \alpha \frac{e^{-\lambda r}}{r} ## where λ and α are positive constants. Calculate the total charge of the distribution. Homework Equations Gauss's law ##Q/\epsilon_0 = \int \vec{E} \cdot d\vec{S}##...
  26. Espoice

    On charge image method over a conducting sphere and its Char

    Hi colleagues, I need your help to figure out some subtle theory problmes I have about this topic. I was thinking about a system composed by a conductive sphere (not grounded) under the effect of a pont charge placed near the sphere. As I know we need two image charges to satisfy the boundary...
  27. H

    If r=0 then will the electric charge of two points=infinity?

    I found that the electric field at r=0 equals infinity. What if two negative charges were put infinitely close together so the electric field was infinite, then would the charge of those two points be -infinity as well?
  28. P

    Charge density of capacitor plates

    Homework Statement A parallel plate capacitor is made of two flat horizontal conducting plates in a vacuum, each of area A, separated by a small gap. One plate carries a total charge 2Q, the other a total charge −Q. Find the surface charge densities on the four horizontal metal surfaces in...
  29. Pushoam

    Point charge outside a grounded conducting sphere

    Homework Statement Homework EquationsThe Attempt at a Solution Option (a), because the potential is 0 on the surface, and potential due to point charge is positive so there must be negative charge on the surface. Since opposite charges attract each other, there is an attractive force...
  30. Lucas Silva

    Gauss' Law: Charge of a Hydrogen Atom

    Suppose the hydrogen atom consists of a positive point charge (+e), located in the center of the atom, which is surrounded by a negative charge (-e), distributed in the space around it. The space distribution of the negative charge changes according to the law p=Ce^(−2r/R), where C is a...
  31. S

    Millikan Oil Drop Experiment: Determining Elementary Charge

    Homework Statement Calculate the charge on each oil drop and determine the elementary charge on an electron given the following: Voltage (Attached) d (Distance between two charged plates) = 0.10m m (Of the droplet) = 1.57x10^-15 kg g = 9.8 kgm/s^2 Homework Equations q = mg*d / ΔV The Attempt...
  32. G

    Difficulty with a Point Charge Particle in Electrodynamics

    Point Particle in Relativity and Electrodynamics: “The Classical Theory of Fields” – by Landau and Lifshitz, in its discussion about classical size of a particle, concludes that:- Thus we come to the conclusion that in classical (non-quantum) ‘relativistic mechanics’, we cannot ascribe finite...
  33. Pushoam

    Flux through an infinite plane due to a point charge

    Homework Statement A point charge q is located a distance d meters from an infinite plane. Determine the electric flux through the plane due to the point charge. [/B] Homework EquationsThe Attempt at a Solution I consider another infinite plane at a distance d in the opposite direction. Now I...
  34. Pushoam

    Flux of a point charge through a circle

    Homework Statement Homework EquationsThe Attempt at a Solution I will try to choose the correct option using the common sense instead of solving it. As d decreases, the flux should increase. For R>>d, only option (a) and (d) satisfy this condition. Now, for choosing between (a) and (d)...
  35. allison west

    Semi-infinite slab of charges -- find E and charge density

    Homework Statement A semi-infinite (infinite in y and z, bounded in x) slab of charges carries a charge per unit volume ##\rho##. Electric potential due to this slab is a function of horizontal distance, x from the center of the slab. It is linear for ## x \lt -1m## & ## x \gt 1m##, and is...
  36. T

    Does a Wire in an AC Circuit Have a Surface Charge Distribution?

    I have a simple AC circuit. For example a battery with a capacitor. In the steady-state the capacitor has the same V of the battery. The wire that connect the two components is a very small cylindrical conductor, so it should have a surface charge distribution. It's that correct ? If no, why ?
  37. R

    Particle motion + electric field when voltage varies

    Homework Statement Two parallel plates located at a distance "L" from each other they maintain a potential difference "V" because of a battery (as shown in the picture). Through a small hole, made in bottom plate, electrons get into system (with mass "m" and charge "-e"), with velocity "v" and...
  38. Kara386

    Particle track detector to measure the charge of a particle

    Homework Statement The detector is made of two co-planar layers of silicon two metres apart, and there is a plane of wire chambers halfway between them. The wire chamber can measure a track with precision ##100\mu##m. What is the highest momentum a particle can have for which the detector will...
  39. Milsomonk

    How to Express Charge Q Using Creation and Annihilation Operators in QFT?

    Homework Statement Express the charge Q in terms of the creation and annihilation operators. Homework Equations $$\phi_{(x)}=\int \dfrac {d^3 p} {(2\pi)^3} \dfrac {1} {2 \omega_p} (a_p e^{i x \cdot p} + b^{\dagger}_{p} e^{-i x \cdot p})$$ $$\pi_{(x)}=\dfrac {-i} {2}\int \dfrac {d^3 p}...
  40. I

    How to calculate formal charge in Nitrite Ion?

    1. The problem statement, all variables, and given/known data How to calculate formal charge in Nitrite Ion Homework Equations How to calculate formal charge in Nitrite Ion The Attempt at a Solution I have counted the total violence electrons 5 + 6 (2) + 1 = 18
  41. I

    Total energy of charge in parallel plate capacitor

    Homework Statement Find the total amount of energy of a charge (q) initially at rest placed at the left plate of a parallel plate capacitor. The left plate is at V = 0, the right plate at V = V0 and the plates are a distance L apart. Homework Equations Etot = 1/2 mv2 + qφ(x). φ(x) = Vx/L The...
  42. T

    Bound surface charge of a cylinder

    Homework Statement Consider a cyclinder made of linear dielectric material with uniform dipole distribution. An externally applied field ##E_{ext}## is applied in the direction parallel to the axis of the cyclinder. What are the values of the bound chrages at the surface. Homework Equations...
  43. DoobleD

    EM wave generation using a single charge in a vaccum?

    I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vacuum ? In practice, when we create EM waves, we (always ?) have opposite charges oscillating, like with a dipole antenna : In the dipole antenna case, I can see how the fields detach...
  44. A

    External Forces and Potential Difference

    Homework Statement The work done by an external force to move a -8.0 uC charge from point a to point b is 25*10^-4 Joules. If the charge was started from rest and had 5.2 * 10^-4 Joules of kinetic energy when it reached point b, what must be the potential difference between a and b? Homework...
  45. I

    Why is there a negative charge on the oxygen atom with the single bond?

    My question is that why is the negative charge on the oxygen atom with the single bond, why not on the oxygen atom with the double bond? I am confused. Source: https://chem-net.blogspot.in/2012/01/simple-procedure-for-writing-lewis.html
  46. reddvoid

    Energy consumed in a digital circuit

    I have a digital circuit , to find the energy consumed by the circuit, I am monitoring the current drawn from the supply and integrating it to get the charge pumped into the circuit ... and the total charge*V supposed to give me total energy consumed by the circuit. But I am getting a small...
  47. A

    Finding the final speed of a Positive and Negative Charge

    Homework Statement This is an example problem I found on khan academy and it didn't have an official problem statement... So I am going to have to make up my own problem statement from what was given. I can link the video if any of you want to see it. A positive charge 4uC and a negative...
  48. S

    Electrostatic Force - Locations of a second charge

    Homework Statement A force of 2.4N [L] is exerted on a -1.8x10-6C charge 0.2m away. What are the possible charges and locations of the second charge? Homework Equations FE= kq1q2 / d2 The Attempt at a Solution Rearranging the equation above for q2 is q2 = FE x d2 / kq1 and substituting...
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