Point Definition and 1000 Threads

The potential of a dipole distribution at a point ##P## is: ##\psi=-k \int_{V'} \dfrac{\vec{\nabla'}.\vec{M'}}{r}dV' +k \oint_{S'}\dfrac{\vec{M'}.\hat{n}}{r}dS'## If ##P\in V'##, the integrand is discontinuous (infinite) at the point ##r=0##. So we need to use improper integrals by removing...

First of all, Let me present some of the things I found from research. (considering convex lens) Interpretation 1 => Focal length is the distance from the center of the lens to the point where all rays converge. Interpretation2 => Focal length is the distance from the point of convergence to...

Homework Statement I'm a bit confused on when a force creates a moment about a point, and when it does not. In particular, in the attached diagram, would F be able to produce a moment about point A? I initially thought that wouldn't be possible as A lies on the same line as F, but since F does...

If we have a point charge of significant value, would osciloscope measure voltage if we just point the electrodes in two diffrent point in space?

<Moderator's note: Member has been informed to separate different question into different threads in the future.> 1. Homework Statement Please see picture attached... The diagram shows the curve with equation y = f (x) The coordinates of the minimum point of the curve are (–2, –1) (a) Write...

I have three points: A, B and C, which are all on the surface of the same sphere. I need to find the xyz coordinates of C. What I know: - the radius of the sphere - the origin of the sphere - the xyz coordinates of A and B - the arc distance from A to C and from B to C - the angle between AB and...

Assuming the point charge lies at the origin, what is the electric field at the origin? Zero or undefined?

Homework Statement A charge q1 is at rest at the origin, and a charge q2 moves with speed βc in the x-direction, along the line z = b. For what angle θ shown in the figure will the horizontal component of the force on q1 be maximum? What is θ in the β ≈ 1 and β ≈ 0 limits? (see image) Homework...

Conceptual question here. Not really positive if it should be asked here or in general physics... In U.S. grid power supply could the secondary winding in a step-down transformer providing split phase power be grounded at any point in the winding? Instead of calling the center tap neutral, if...

Hi, I need help with this problem: Homework Statement Condition: an object has to move from point A to point B in the least time possible. The distance between the points is L. The object can accelerate (decelerate) with a fixed acceleration ##a## or move with a constant speed. What maximum...

Homework Statement I've attached a picture of the circuit below for reference, but the question is asking what the potential is at point D.Homework Equations V = IR[/B]The Attempt at a Solution I was told that the answer was 9V, but I'm a little confused because I thought if I looked at the...

https://phys.org/news/2019-01-galaxies-physics-cosmic-expansion.html can dark energy vary over the history of the universe?

Homework Statement A point moves rectilinearly in one direction. The figure shows the distance s traveled by the point as a function of time. Using the graph, find: The average speed of the point during the movement time. Maximum speed The moment t0 in which the instantaneous speed is equal to...

Assumptions: 200+ years from now Asteroids have been moved to all Lagrange points, and at least 90, 180, and 270 degrees on Earth's' orbit for mining, and shielding humans and equipment Tech to acceleration/decelerate at 1 gravity without need to carry fuel. (My main fiction.) Direct line of...

Homework Statement A distribution of charge with spherical symmetry has volumetric density given by: $$ \rho(r) = \rho_0 e^{ \frac {-r} {a} }, \left( 0 \leq r < \infty \right); $$ where ##\rho_0## and ##a## is constant. a) Find the total charge b) Find ##\vec E## in an arbitrary point...

Homework Statement https://www.physicsforums.com/threads/find-the-electric-field-in-the-point-p-of-a-right-triangle.965285/#post-6125768 knowing that the three charges are equal and that the angles of the triangle are 90°, 45°, 45°. Homework Equations The Attempt at a Solution I tried...

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...

Take for example dimensional regularization. Is it correct to say that the main point of the dimensional regularization of divergent momentum integrals in QFT is to express the divergence of these integrals in such a way that they can be absorbed into the counterterms? Can someone tell me what...

Homework Statement In the figure above, charge A is -5.00 nC, charge B is 10.0 nC, and charge C is 5.00 nC. If x = 2.10 cm and y = 4.20 cm, what is the electric field at the dot? Homework Equations E = kq/r^2 The Attempt at a Solution r = distance from A to point = sqrt(x^2+y^2) Ea = kq/r^2...

Homework Statement Find the electric field of a point outside sphere without using Gauss's law. (Do not evaluate the integral) Homework Equations Coulomb's Law Spherical Co-ordinate System The Attempt at a Solution I have attached my attempt as a picture but now I am stuck, I don't know how I...

A charge Q is placed at the centre of the square of side 2.90 cm, at the corners of which four identical charges q = 6.5 C are placed. Find the value of the charge Q so that the whole system is in equilibrium. Can someone help me figure out where I have went wrong, I began by finding the force...

We were informally introduced Taylor series in my physics class as a method to give an equation of the electric field at a point far away from a dipole (both dipole and point are aligned on an axis). Basically for the electric field: $$\vec E_{axis}=\frac q {4πε_o}[\frac {1} {(x-\frac s 2)^2}-...

Homework Statement You make repeated measurements of the electric field ##\vec E## due to a distant charge, and you find it is constant in magnitude and direction. At time ##t=0## your partner moves the charge. The electric field doesn't change for a while, but at time ##t=24## ns you observe a...

Homework Statement When a point charge is positioned at the origin = 0 in an isotropic material, a separation of charge occurs around it, the Coulomb field of the point charge is screened, and the electrostatic potential takes the form \phi(r) = \frac{A}{r} \exp\left( -\frac{r}{\lambda}...

I have to test a Current transformer. I read knee point is a point at which 10% increase in voltage leads to 50% increase in current. As there are different classes of current transformer (cores), how it is decided what/how much will be the knee point voltage of that core.

I'm confused (what else is new) about L2. While watching a video from PBS Digital Spacetime about the latest data drop from Gaia Space Telescope, Matt O'Dowd showed a CGI animation of the telescope leaving Earth then circling/orbiting L2 perpendicular to the Earth/sun plane. I thought that the...

Hey Guys, I posed this on Math Stackexchange but no one is offering a good answering. I though you guys might be able to help :) https://math.stackexchange.com/questions/3049661/single-point-continuity-spivak-ch-6-q5

So I was having a discussion with one of my teachers and they mentioned along the way in my PhD, I would learn how to formulate and/or understand where a question is coming from, be able to solve it and know exactly when I arrive at a satisfactory conclusion. This would be quite a handy skill...

Homework Statement A wire carrying a current I in the positive x direction is located along the x axis. The wire is of finite length and is located between x = -L and x = L. Find the magnetic field at a field point located a distance a away from the wire. Homework Equations Biot-Savart law...

Homework Statement I set the derivative to 0. i get 1 real root a max point and 2 imaginary. How can i find that local min? what techniques are available?

Homework Statement Find the shortest distance from P(-4,2,6) to the plane 2x-3y+z-8=0. Homework Equations ##|proj_\vec n \vec PQ|=|(\frac {\vec PQ \cdot \vec n} {\vec n \cdot \vec n})| |\vec n|## The Attempt at a Solution I kind of had to guess some steps because it was done differently in...

Homework Statement Suppose a line is given, say (x-3)=(y-2)=z in Cartesian form and we are supposed to find a point on it which is at a distance say, 6 units from a given arbitrary point (1,2,3). 2. Relevant tedious methods 1) write line in vector form then equate modulus of vector between...

I am reading Loring W.Tu's book: "An Introduction to Manifolds" (Second Edition) ... I need help in order to fully understand Theorem 2.2 and the remarks after the theorem ...Theorem 2.2 and the remarks after the theorem read as follows: My questions on the above text from Tu are as follows...

Hello everyone. I am triyng to calculate the route which takes less time to go from point A to point B in the presence of a constant flow (I. E. a simple version of Zermelo's navigation problem) using the GAMS software. However, if I put both points on a straight line and make the constant flow...

1. The problem statement Two charges of 3μC and -2μC are placed 2cm apart. At what point along their connecting line is electric potential zero? Homework Equations Electric potential superposition Φ=Φ1-Φ2 since q2 is negative Φ=kq/r^2 The Attempt at a Solution Let’s say the charges are on the...

Hello! Dear Forum Members, I'm searching 4 point probe head on internet but i could'nt find it. Could you help me find it?

Homework Statement Find the magnetic field at point P. (P is at the centre of two infinitely long wires, carrying current in opposite direction. Homework EquationsThe Attempt at a Solution My guess is that since the current direction is opposite and distance between the point and the wires is...

Homework Statement Please look at the attached screenshot. This problem is really confusing for me and I can't seem to make much sense out of it. Homework Equations Ei = Ef The Attempt at a Solution As you can see, I did get (a). (The other checkmarks, I guessed — there were only two...

Sometimes there are functions that are initially defined for only integer values of the argument, but can be extended to functions of real variable by some obvious way. An example of this is the factorial ##n!## which is extended to a gamma function by a convenient integral definition. So, if I...

I had heard an opinion from my high school teacher, but I can't understand?? "An experimental record of a French scientist. He heats the diamond and sublimates it. After cooling, it turns back to solid barbecue carbon. In this case, although there is a physical transition, the substance seems...

So I have been wondering: The potential for a point charge at the origin, is described as: (Using the reference point at infinity): V=1/(4πε) * q/r My question is, what happens to this Potential the closer we are to the point charge, and so the closer we would get, the Potential seems to go...

a student earned grades of A, C, A, A, and B. Those courses had these corresponding numbers. of credit hours:1,6,3,1,3. The grading system assigns quality points to letter grades as follows: A=4, B=3, C=2, D=1, and F=0. Compute the grade point average (GPA) and round the result to two decimal places

Hi guys, I posted about a closely related subject earlier, but with more and more research, all I have found regarding fusion energy is pure pessimism, and that it will always be a theoretical hope that just won’t happen. For example, the Bulletin of Atomic Scientists basically says that...

Homework Statement In the figure attached, what is the torque about the pendulum's suspension point produced by the weight of the bob, given that the mass is 40 cm to the right of the suspension point, measured horizontally, and m=0.50kg? Homework Equations tau = rFsin (theta) or tau = lF...

Hi All I am trying to understand a stress / strain curve for a ductile material. But I am struggling with understanding the difference between the Elastic Limit and the Yield Point. I define these terms as:- Elastic Limit - Is the point on the stress/strain curve where the material will...

Hi, I'm stuck on a homework problem in my Calculus III class. I solved 3a really easily, but 3b is giving me a lot of trouble. I know that to find the tangent line, I first have to find the slope, which is represented by the vector: <3cos^2(t)(-sin(t)), 3sin^2(t)(cos(t))>. I know the formula...

I have come across a questions which reads "Why does even photon travel?". After reading special and general theory of relativity, this one bugs me all over. For a particle moving closer to speed of light, clock slows down and the space around it contracts. I see a photon travel and I see things...

My problem reads as follows: Point p=(3,3√3) is rotated counterclockwise about the origin by 75 degrees. What are the coordinates after this rotation? I have no idea how to rotate a point, let alone by 75 degrees.

I've been thinking about this problem and would like some clarification regarding the value of the divergence at a theoretical point charge. My logic so far: Because the integral over all space(in spherical coordinates) around the point charge is finite(4pi), then the divergence at r=0 must be...

In @A. Neumaier 's excellent Physics FAQ, he notes under "Are electrons pointlike/structureless?" that "Physical, measurable particles are not points but have extension. By definition, an electron without extension would be described exactly by the 1-particle Dirac equation, which has a...