Potential Definition and 1000 Threads

Homework Statement In the diagram, m1 has a mass of 47 kg and m2 has a mass of 35 kg. The coefficients of friction between m1 and the surface of the inclined plane are µs = 0.42 and µk = 0.19. (a) If the masses are held in place and then released, will they start to move? (b) If the answer...

Griffith says in problem 1.15 the potential energy has an imaginary part. my question is that any real case exists where the part of the potential energy is imaginary?

Can someone please show that calculation of gravitational potential energy at a point R+h from the centre of the Earth by choosing the centre of the Earth to be at zero potential. Here R is the radius of the Earth and h is not very small wrt to R

Can somebody give me some insights related to spin chemical potential ? I searched on google but didn't get satisfied. What it means when two spin groups of electrons (group A with spin up and group B with spin down)have different spin chemical potential?

Homework Statement The figure shows part of a complete circuit. The potential at point A is greater than that of B by 19 volts what is the potential difference in volts across the three microfarad capacitor? Homework Equations All relevant to electric circuits The Attempt at a Solution From...

We have set the Earths' Voltage at zero volts but is this 'earth voltage' applicable throughout the Universe. If not, is it relative in the same manner as spacetime and is it calculatable?

So we know that the E-field between two parallel plates is constant and that the potential difference between the plates is just the E-field times the distance between the plates. Let's say we're moving a positive charge from a negatively charged plate to a positively charge plate ( or near)...

I've now found a different way to look at potential energy and its location in the Newtonian approximation to relativistic gravity which may perhaps shed some light on how the corresponding terms work in GR. This is related to a previous thread of mine on "Pressure and Newtonian potential...

Homework Statement There is a uniform electric field=100 V/m inclined at 45 degrees with the x axis. My doubt boils to which is greater? V(0,0) or V(10√2,0) (since my answer has the wrong sign) Homework Equations All electrostatics formulas The Attempt at a Solution The work done to move a...

Homework Statement A solid non-conducting cube of side l and uniformly distributed charge q, has electric field E and potential V at one of its vertex, imagine this cube to be made of 8 smaller cubes of side l/2. if one such cube is removed, find the new field and potential at the point where...

EDIT: Problem is FIXED. Hello, I'm trying to understand Ewald Summation and finally found a great link (http://micro.stanford.edu/mediawiki/images/4/46/Ewald_notes.pdf) that I could follow in the five first pages. But then I'm blocked by a rather odd formulation p. 5, after eq. (25): "where...

1. Homework Statement Hello, I'm learning electricity and I'm having a few conceptual questions regarding the subject ( especially about neutral objects ) which I'm unsure of the answers and I'd be happy if someone could help me:1. Is the charge density of a neutral object ( doesn't matter if...

In classical physics electrostatic potential energy is: ##U=k_e\frac{q_1q_2}{r}## So amount of potential energy is not limited as ##r\rightarrow 0## But obviously potential energy (= binding energy) is limited by masses of charge carrying particles. Say when electron and positron annihilates...

Homework Statement I'm given that there is a positive charge of 1 nC at x=0.25 m and a negative charge of -1 nC at x=-0.25 m. I've calculated the potential created at different points along the x-axis by the positive charge and the negative charge using the formula, $$V=\frac{kq}{|r|},$$ where...

I am hoping to get a deeper understanding of the difference between two different gravitational potential energy equations, the first of which is given by U = mgh and the second given by U = (Gm1m2)/r I first assumed that in a system consisting of the Earth and, say, a tennis ball, these...

Hi I need help to understand how electric potential could be zero at the center of two equal but opposite charges. It seems, there is a no field free region anywhere inside the space between the charges. If I move a test charge from negative to positive charge or otherwise, there seems to be no...

In thermal physics entropy S is regarded as a system variable in 1st theorem of thermal dynamics, i.e. dE(S,V)=TdS-pdV=T(S,V)dS-p(S,V)dV Entropy is regarded also as thermal potential,i.e. dS(E,V)=\frac{1}{T(E,V)}dE + \frac{p(E,V)}{T(E,V)}dV S,V,p,T are usually regarded as variables. My...

The electric field of an infinite conductor of net charge Q along the x-y plane is easily found using Gauss's Law: $$ \vec E(x, y) = \frac {\lambda} {2\pi \epsilon}\frac {[(x-x_c)\hat x + (y-y_c)\hat y]} {[(x - x_c)^2 + (y - y_c)^2]^3}, $$ where ##x_c## and ##y_c## mark the location of the...

Homework Statement From Griffiths Third Edition: "Introduction to Electrodynamics" p.p. 81 ex. 2.6 "Find the potential inside and outside a spherical shell of radius R, which carries a uniform surface charge. Set the reference point at infinity. Homework Equations V(r) = -∫E⋅dl The...

Can anyone know please know how can i impose the electrode surface potential to vary lineary and periodically with time as: E(t)= phimin+v*t for 0<=t<t0 phimax-v*(t-t0) for t0<=t<2*t0 with t0=(phimax-phimin)/v v=scan rate in V/s

Disclaimer: I am not a physicist, just trying to learn some parts of it in my free time. And I do not mean to propose any kind of "new-theory" with my question. I always thought that Maxwell equations in their differential form for B and E may be reformulated/updated to include a magnetic...

What I know gravitational time dilation (based on GRT) is dependent on gravity potential and not on gravitational acceleration. That would mean, that for example in center of Earth is the gravitational acceleration zero, but the gravitational potential is bigger than on the surface of Earth...

In Griffith's electrodynamics chapter 2 example 7 he calculates potential due to a spherical shell outside it. Here E is radially outward while dr is radially inward as we are going towards the sphere hence E.dr should be negative but it is taken positive?

Do electromagnetic waves have potential and kinetic energy like springs, strings, etc. If so how are they calculated, inter-related? What is the total energy? Are the energies fluctuating over time? I am a physics hobbyist so generally the first answers should come with the least mathematics...

Homework Statement A copper wire and an iron wire of equal length l and diameter d are joined, and a potential difference V is applied between the ends of the composite wire. Calculate the potential difference (in volts) across the iron wire. Assume that l = 2.00 m., d = 0.30 mm., and V = 156...

Homework Statement Two charges, A (-3 C) and B (+4 C), are placed 2.40 m apart. Point X is 30 cm from A, and Point Y is 30 cm from B. What is the electrical potential difference going from X to Y? Homework Equations W = △Vq The Attempt at a Solution Teacher gave answer as 6.9 x 10^4 V I am...

I have a question with regard to split single phase (in United States) electricity. I understand that there are 2 hot legs each 180 degrees out of phase at +120v and -120v (240v between hot legs) going from transformer to breaker box and a center tapped neutral Earth bonded wire at 0v with...

Homework Statement part d) from the following question please Homework EquationsThe Attempt at a Solution [/B] sol attached So I see that the idea is that it is a maximum so to set ##\dot{r}=0## and then the maximum value is dependent on some values of J and K, to get the equation. But...

Homework Statement I would like to ask about parts c) and d) , the graph sketching bits. 2. Homework Equations ##V(r) = ( \frac{J^2}{r^2}+\epsilon)(r-\frac{1}{r}) ## where the value of ## \epsilon ## is set according to whether time-like or null etc. The Attempt at a Solution Q1)for...

Let's suppose I have a potential well: $$ V(x)= \begin{cases} \infty,\quad x<0\\ -V_0,\quad 0<x<R\\ \frac{\hbar^2g^2}{2mx^2},\quad x\geq R \end{cases} $$ If ##E=\frac{\hbar^2k^2}{2m}## and ##g>>1##, how can I calculate how much time a particle of mass ##m## and energy ##E## will stay inside...

Let's suppose I have a finite potential well: $$ V(x)= \begin{cases} \infty,\quad x<0\\ 0,\quad 0<x<a\\ V_o,\quad x>a. \end{cases} $$ I solved the time-independent Schrodinger equation for each region and after applying the continuity conditions of ##\Psi## and its derivative I ended up with...

Hello, I'm struggling to understand how the electric potential difference is measure especially when a distance is not given. For instance in Serway, on the explanation of the Van de Graaff Generator the authora write, "Van de Graaff generators can produce potential differences as large as 20...

Homework Statement Light with a wavelength of 630nm is directed at a metallic surface that has a work function of 1.5 eV. Find:a) The maximum kinetic energy of the emitted electrons. b) The cutoff potential required to stop the photoelectrons. Homework Equations Ek = hc / λ - W Ek = eVo...

I am aware that the negative derivative of potential energy is equal to force. Why is the max force found when the negative derivative of potential energy is equal to zero?

I read somewhere PE=KE, how? It mean we can get transfer 100% PE to KE and KE to Joule Please anyone can explain? If I throw mass of 1000kg from 50 meters height can I get energy equal to Pe=mgh = 1000*9.81*50=490500 Joule? It mean 490500Kn = 490500watt= 490.50Kw. Is it possible to to get this...

Bee Hossenfelder's blog has a discussion: http://backreaction.blogspot.com/ Preprint: https://arxiv.org/abs/1805.12028 New evidence in the search for the 'sterile' neutrino. Can someone comment on this please. @mfb

How can I calculate the loss of potential energy when forces are applied but no motion in the system occurs? Here's an example: Let's say I build a battery operated car that is set to drive forward, but I put it right in front of a wall. It attempts to drive forward, but instead it just pushes...

Homework Statement Let a charge oscillate on a straight line between -a to +a with a frequency ω and according to the law: κ (x.t) = κ° sin(πx/a) e^(-iωt) I have to find the following: 1. Vector potential in the dipole approximation 2. Integral of the intensity of radiation Homework...

Homework Statement A plane z=0 is charged with density, changing periodically according to the law: σ = σ° sin(αx) sin (βy) where, σ°, α and β are constants. We have to find the potential of this system of charges. Homework EquationsThe Attempt at a Solution [/B] I...

Homework Statement A solid insulating sphere of radius a = 3.6 cm is fixed at the origin of a co-ordinate system as shown. The sphere is uniformly charged with a charge density ρ = -215 μC/m3. Concentric with the sphere is an uncharged spherical conducting shell of inner radius b = 11 cm, and...

Homework Statement Assume a conducting sphere has a radius of 3400km with an electric field of 100 V/m at it's surface. a) Calculate total charge of sphere. b)Calculate potential at the surface using infinity at reference point c) Calculate capacitance of the sphere using the result of a or b...

Homework Statement The Attempt at a Solution [/B] Hi All, I'm having trouble answering part (f) of the above question. I have managed parts (d) and (e) fine but am not sure how to proceed with part (f). I am pretty sure that the amplitude of the reflected wave in region 1 will be zero...

Hello, I have a question on electric potential, potential energy and work. ##\Delta V = \frac{\Delta U}{q_o}## ##W = q_o\Delta V## ##W = -\Delta U## Example: A point A that is closer to the source charge than point B, then the electric potential difference is negative (##\Delta V = V_B -...

Homework Statement Homework Equations What makes the shape circular/ parabolic? what determines the direction? The Attempt at a Solution Because the furthermost plate is positive, the proton would be repelled towards the screen, so i or iii. How do I know the shape?

Homework Statement Sorry, the post isn't about a single homework problem but rather something that I keep getting confused on. It's about calculating the electric potential of a spherical shell of uniform charge in two different ways. Homework Equations ##\Delta V=\int_a^b -\vec E\cdot d\vec...

Homework Statement Q1: There are two concentric spherical shells with radii ##R_1## and ##R_2## and charges ##q_1## and ##q_2## uniformly distributed across their surfaces. What is the electric potential at the center of the shells? Q2: There is an infinitely long hollow cylinder of linear...

Homework Statement Homework EquationsThe Attempt at a Solution When we will move the contact X towards P, the potential difference should be maximum across the potential divider. I work out A as my answer but I think it is wrong.

Homework Statement Project Thor is a proposed (and terrifying) weapon system where a cylindrical tungsten rod (19600 kg m3 ) about the size of a telephone pole (6.10 m long and 0.300 m in diameter) is dropped from Earth orbit. Imagine you dropped one of these from an orbit 10,000 km above the...

I have 3 questions. After thinking about it I feel these questions may indicate that I have some misunderstanding in basic knowledge or some missed parts. 1. Why is the (time independent) wavefunction an exponential decay inside the potential barrier? I know the mathematical derivation, but I am...

There seem to be two ways of defning what a vacuum is in QFT: 1. It is state $|0\rangle$ such that $$a_k|0\rangle = 0$$ for all anihilation operators $$a_k$$, with creation operators $$a_k^{\dagger}$$. Thus, it is defined in Fock space. 2. It is state $$|0\rangle$$ such that derivative...