1. Reneee

    What is the work done to move this Charge?

    I found two formulas to calculate the work done. One is with this path integral: ## W_{AB}## = W(## r_A,r_B ##)=q* ## \int_{r_A}^{r_B} E*dr ## but here is the one I tried to use: ## W_{AB}## = q*Δ U = q*(## \frac {kQ} {r_A} ## - ## \frac {kQ} {r_B} ## ) Now heres my problem, what are...
  2. C

    Why Potential Energy cannot be included twice?

    If for example I have two charged particles q_1 , q_2 with distance 'r' between them, then: The potential energy that results from particle q_1 exerting force on particle q_2 is $$ k\frac{q_1 q_2}{r} $$ If I do the same process for particle q_2: The potential energy that results...
  3. S

    Battery Charge and Discharge Time Calculations

    I am performing some calculations but struck with confusion whether I am doing it correct or wrong due to contradictions of these calculations on different calculators websites. I hope here someone will help me with the validation of my calculations. Battery Capacity = 150 Ah Battery...
  4. M

    B Question about conservation of angular momentum for charges

    Why is angular momentum conserved for a charge in an electric field?
  5. C

    I A Couple Magnetism Questions

    Hello, there are a couple things about magnetism that I do not understand. 1. Why didn't we define the magnetic field to be in the directions of the force? This isn't really a technical question, I am just more curious about why it is this way. The way I was thinking of it, the math seems to...
  6. L

    Loading/charge time of an electromagnet

    Hej Guys, Did anyone see anywhere an equation to this? If nothing else then a loading time formula for solenoid would do. Thank you!
  7. astroman707

    Charged pendulum problem

    Homework Statement A cork ball is suspended at an angle from the vertical of a fixed cork ball below. The mass of the suspended ball is 1.5x10^-4 kg. The length of the suspension thread is .1m. The fixed ball is located .1m directly below the point of suspension of the suspended ball. Assume...
  8. L

    Flux Through a Cube's Face with our Point Charge at a Corner

    Homework Statement A charge q is placed at one corner of a cube. What is the value of the flux of the charge's electric field through one of its faces? Homework Equations The flux surface integral of an electric field is equal to the value of the charge enclosed divided by the epsilon_naught...
  9. Kaan99

    Electrostatic self-force is zero

    Homework Statement Consider a charged body of finite size, (\rho=0 outside a bounded region V). \vec{E} is the electric field produced by the body. Suppose \vec{E} \rightarrow 0 at infinity. Show that the total self-force is zero: \int_V \rho \vec{E} dV = \vec{0}, i.e. the charged body does not...
  10. Lilian Chan

    Charges and Trig question

    Homework Statement link: What is the magnitude of this force? Homework Equations Coulomb's Law Trig equations The Attempt at a Solution (.05 m)xcos(60)=0.025m (the distance between the two known charges) F(between the two known...
  11. T

    Charge Density Expression

    Homework Statement A charge Q is uniformly distributed throughout a nonconducting sphere of radius R. Write the expression of the charge density in the sphere? Homework Equations Charge density ρ=dQ/dV Gauss's Law ∫EdA = E(4ϖr^2) The Attempt at a Solution If Q is uniform then ρ=Q/dV and the...
  12. M

    Spin of a nucleus within an external magnetic field.

    When a nucleus is placed inside an external magnetic field, it aligns itself parallel to the field, as that is the most stable position for it to be in. In more technical terms: it acquires an alpha spin. When you shine radio waves at this nucleus, it absorbs energy and flips over anti-parallel...
  13. B

    I Question on the work done while charging up a capacitor.

    So the work done when charging up a capacitor is ##dW=VdQ## However, when we add a charge ##dQ## to the capacitor, ##V## also changes accordingly, so I was wondering why the work done wasn't written as ##dW=VdQ+QdV## (one that also takes into account t he change in ##V##). Thanks in advance.
  14. K

    I Charge-Dipole Derivation - Assumption That x >> a

    In this derivation: they assume in equation (8) that x >> a in order to use the Taylor Expansion because a/x has difficult behavior. Why does that assumption work? Meaning, why can we...
  15. S

    Is the following decay process possible?

    Homework Statement An antimuon and electron may bind together via Coulomb attraction and then decay, but is the following process possible? (µ+e-) → νe + νµ_bar *The νµ_bar is the antiparticle of the muon neutrino - the antimuon neutrino More than one answer (below) may be correct. a)...
  16. S

    B Energy, What Is It?

    I have a simple two-part question, or two simple questions. 1. What is energy? 2. What is charge? The charge I'm referring to is the charge on charged subatomic particles. And atom's charge is defined by the number of electrons and protons present in it. But an electron itself is called a...
  17. D

    B Voltage vs charge?

    If voltage is the difference in charge between 2 points, then why for a capacitor of a larger area or thinner dielectric cross section, do they say that it can store more charge given the same apppied voltage? Isnt voltage the difference in charge between 2 points? So if you can store more...
  18. CDL

    Electric Flux through the Face of a Cube

    Homework Statement Griffiths' Introduction to Electrodynamics problem 2.10, Homework Equations Gauss' Law, ##\int_{S} \textbf{E}\cdot \textbf{dS} = \frac{Q_{\text{enc}}}{\epsilon_0}##[/B] The Attempt at a Solution It seems reasonable that the flux through the shaded surface and the...
  19. M

    Radiation field of charge moving in a circular loop

    Homework Statement [/B] I need to calculate de radiation field produced by a charge moving in a circular loop of radius a, considering the motion is not relativistic and zone of radiation (far field) . Homework Equations The scalar potential is: $$ V=\int \dfrac{\rho(x')}{|x-x'|}d^3x'$$ The...
  20. Jalon Young

    Quick Question about a Piezoelectric shoe for project

    I am currently working on a piezoelectric shoe and the objective of the project is to charge a phone I am aware a phone is DC and piezoelectric disc generate AC I know I need a bridge rectifier to convert My question is: Would I generate more volts if I Use a bridge rectifier to convert AC to DC...
  21. S

    I Radiation of matter "free falling" into the black hole

    Hello everyone, "Does a charged particle radiate in free-fall?". I read many threads on this subject and I was surprised to find out that there is no unanimous "Yes or No" answer to this question. Here is an interesting answer from The question is widely discussed in the...
  22. A

    Confusion with constant voltage and dielectric

    Homework Statement Consider a conducting sphere with radius ##R## connected to a voltage source of ##V_0## volts. If the sphere is then covered by a dielectric spherical layer of radius ##9R## calculated the relative permitivitty ##\varepsilon_0## needed so that the field in the empty zone...
  23. M

    Charge distributions of two infinite parallel plates

    Homework Statement Two infinitely large conducting plates with excess charge 2Q and 3Q are placed parallel to one another, and at a small distance from one another. How are the charges 2Q and 3Q distributed? You may assume that infinitely large sheets of charge produce electric fields that are...
  24. Superfluid universe

    I What is the charge for the weak interaction?

    We have the electric charge for the electromagnetic force, the color charge for the strong force. What is the charge for the weak force? Thank you. :)
  25. A

    I Why isn't a capacitor an open circuit?

    I understand the basics of how capacitors work. If you hook one up to a power source, negative charge will build up on one plate, and positive charge will build up on the other plate. As the charges build up, an electric field forms between the plates and a potential difference is established...
  26. A

    I When Electric Field is 0 is potential also 0?

    So here is how my book defined electric potential. If you take a charge, it will have a corresponding electric field associated with it. If you put another charge in that electric field, an electrostatic force will act on it and give it kinetic energy. This kinetic energy can't come from thin...
  27. A

    Confusion about Capacitors

    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...
  28. 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...
  29. 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...
  30. G Cooke

    I 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...