1. S

    Find the speed of a copper loop falling in a magnetic field

    Hi all, so I had this problem and on the exam and I got a solution but I had an mass-term in there which wasn't given. I used Farraday's Law of Induction to get the Voltage induced. Then I used ##rho* \frac{A}{4a} ## for the resistance and divided the Voltage by that to get the current. I then...
  2. D

    50Hz 3 Phase Circuit - Twisting to reduce EMI?

    I have done the maths to work out the Induced Voltage on a communication cable, from a bunch of 3 phase circuits in a panel - with the minimum distance between them I calculated it to be about 1.5nV; but for a larger system where there could be larger loads on the cables I was thinking about...
  3. S

    Force on a copper loop entering into a magnetic Field B with speed v

    Hi, second problem in one evening, I'm sorry! But i'm also not quite sure if I did this one right. I had thought I need lenz's law but there is no current before entering the field so I just use the induced Voltage? My approach: ## V = \frac {B*A}{t} ## ## IR = \frac {B*A}{t} ## and ## A = v*t...
  4. P

    How to calculate the voltage induced in a coil by an AC magnetic field?

    So, as it says in the title, I am trying to calculate overall voltage induced in a coreless coil in the cases of it being stationary and moving in an alternating magnetic field. To go more into detail, I would like to create a mathematical model of a coil in an alternating magnetic field that...
  5. S

    Prove the decomposition of a graph w/ even edges produce a 2-path set

    For my base case I just used a graph with three vertices and 2 edges. Decomposing this would just give us the same graph, which has a path length of 2. The inductive step is where I'm having some trouble: One idea I have is that we take a graph G then inductively remove an edge to create two...
  6. S

    Proof by Induction: Arithmetic Sum

    Hi, I am self studying induction and came across the following problem. I am stuck on how to proceed (I need to use induction, I know there is a direct proof). My proof attempt is as follows: Let ## P (m) ## be the proposition that: $$ \sum_{i = m + 1}^{n} i = \frac{(n - m)(n + m + 1)}{2} $$...
  7. Klaus von Faust

    Interesting Magnetic Field Induction Problem

    1. Homework Statement Suppose we have an isolated, long, narrow straight wire with low electrical resistivity. A constant current ##I## is sent through this wire. We know that if an electron is sent on a path which is perpendicular to the wire, towards it, with an initial speed ##v_0##, and the...
  8. atommo

    B Stupid question relating to electric induction

    Hi, I've been interested in the science behind electrons/magnetism for quite a while. I've been learning quite a bit from various sources online. However there is one thing that's really nagging me. Magnetic fields result from moving electrons. That indicates that a permanent magnet has...
  9. I

    I Maxwell's Law of Induction - How Does it Work?

    So, I was studying Maxwell's equations and I don't really understand the last one - Ampere's Law (with Maxwell's extra term added in). The bit I'm not able to understand is the term Maxwell added. How exactly does a changing electric field through a closed loop induce a magnetic field along that...
  10. Celso

    Induced EMF — generator coil area calculation

    1. Homework Statement What is the necessary area for a generator that produces an emf of ##\mathcal{E} = 150V## when it spins at a ratio of 60 revolutions per second, in a magnetic field of ##B = 0.5 T##? 2. Homework Equations ##\oint_{c} E \cdot dl = \mathcal{E} = -\frac{d}{dt}\iint_{s} B...
  11. U

    Proof via mathematical induction

    1. Homework Statement Use mathematical induction to prove that (8n − 7n − 1) is divisible by 49 for any n ∈ N. Correction by mentor for better readability: ##49\,|\,(8^n-7n-1)## 3. The Attempt at a Solution We can see that the base case is satisfied here: n = 1, 8^1-7*1-1 = 0 and 49 | 0 is...
  12. mheruian

    Winding Direction Consideration (Proper Winding)

    Hello, I'm boy who suddenly been strucked by curiosity on how hand crank generator works and i watch and read some of how to create one, specially this one on youtube: and i want to create one but i don't have a 3D printer, but i saw some alternative but as i do/design my own coil based on...
  13. U

    Calculation of Change in Magnetic Flux Linkage Across a Wire

    1. Homework Statement A straight wire of length 0.20m moves at a steady speed of 3.0m/s at right angles to a magnetic filed of flux density 0.10T. Use Faraday's law to determine the e.m.f. induced across the ends of a wire. 2. Homework Equations E= Nd Φ/dt but N=1 so E= dΦ/dt 3. The Attempt...
  14. R

    Solar PV:What happens to the lost energy?inductive recovery?

    Hi there, I am new in here, thanks for any reply. I took same title of a previous closed 3D by pranj5. As understood main part of the energy absorbed by PV panels goes in reflection and heat. The heat origins mainly in electrons that are excited but not enough to jump or they jump but they...
  15. J

    I Faraday's Unipolar Induction Equation

    Hello all, I have a question regarding Maxwell's Equations and Faraday's unipolar induction equation. If we study the case of a cylindrical magnet with a radius of r which is rotating about its axis with angular velocity w. The electrons within the magnet collide with the moving atoms, causing...
  16. Yousuf Ejazi

    Calculate the induced EMF for angle α

    I have a question in my book and it’s confusing me a bit. I tried to search online for similar solved problems but couldn’t succeed. So here it goes: Calculate the induced EMF in a conductor loop when the angle between \vec{A} ~ and~ \vec{B} ~is~ changed ~from ~{0 °}~ to ~{α °} in 1...
  17. N

    Induction: Electromagnet and Aluminium Ring

    I need some help with this task, I am stuck. 1. Homework Statement An aluminium ring is placed on top of an elctromagnet. a. The electro magnet is connected to AC. What will happen with the aluminium ring? Motivate your answer. b. What will happen with the ring if the electromagnet is...
  18. G

    Sign of the Faraday-Lenz equation

    1. Homework Statement Hello, good afternoon, I have a question that's coming up when I'm doing electromagnetic induction exercises. In some exercises they ask me to determine the electromotive force (iee), and when they do the exercise resolution they do it with absolute value. In other...
  19. nomadreid

    I Hilbert's omega rule, induction, omega-consistency

    As I understand Hilbert's omega rule for a first-order proposition P over the natural numbers, P(0) &P(1) &P(2) &..... ⇒ ∀n∈ℕ P(n) :star: which seems to be the same as ω-consistency. Is there a difference? Further, the axiom schema of induction has each axiom for a proposition P over the...
  20. Shadow89

    Optimal values for power in an induction heater?

    I really want to build a simple but powerful induction heater for hobby blacksmithing. Metal shaping and the design of the cooling system within the coils are not a problem. I need help understanding the electronics Obviously I must first use a transformer as a safety against "backlash" to the...
  21. ?

    EM fields of two opposite moving point charges

    I wrote and solved this problem but am having serious doubts about the answer I obtained. 1. Homework Statement Two point charges \pm q move along the z-axis with velocity \pm v. If they are at the origin when t=0, what is the electric field magnitude a distance r from the z-axis? 2. Homework...
  22. K

    B Why the voltage on the primary coil changes in an induction stoveplate?

    Translated from Norwegian high-school physics book: I wonder how and why does the voltage change on the primary coil when the cookware is removed or boiled over?
  23. Cardinalmont

    I Short Circuiting the Secondary of a Transformer/Self Impedence

    Thank you for reading my post. I was watching the video this video on transformers and saw an amazing demo: From 4:00-5:20 the guy does an experiment where he has a simple transformer circuit set up: On the primary side of the transformer he has an AC power supply, and a lightbulb. On the...
  24. T

    Mechanics II: Feynman Paradox

    I am currently going through a friend's Mechanics II notes and homework before I take the course at a different university next semester. I have a few problems that I am having trouble understanding and am posting here for help. 1. Homework Statement 1. A solenoid is on, Flux is Φ. 2. The...
  25. FlimFlam

    I Grass under powerlines

    So I was messing with the induction from power lines and fluorescent bulbs, and I noticed all the plants under the power lines were dead but plants around it were fine. Do EMF's have something to do with this?
  26. D

    I Induction axiom

    So , what I was wondering about was a slight difference in notation, for which I am not certain if correct (mine, in particular.). The induction axiom says: If M is a subset of ℕ, and if holds that: a)1∈M b)(∨n∈ℕ)(n∈M→s(n)∈M) then M=ℕ. Now my question is: why do we write (∨n∈ℕ)(n∈M→s(n)∈M)...
  27. VSayantan

    Speed of a Magnet Falling through a Conducting Wire

    1. Homework Statement A small but very powerful bar magnet falls from rest under gravity through the center of a horizontal ring of conducting wire, as shown in the figure below (on the left). The speed-versus-time graph, in arbitrary units, of the magnet will correspond most closely to which...
  28. F

    B What's the relationship between drop height and induced emf?

    In my experiment, I intended to find out how the change in the bar magnet drop height from solenoid affected the emf induced in the solenoid, however, I am unable to come up with an equation that shows a relationship between the two variables. I have thought of Biot-Savart law, but I do not...
  29. R

    Adding a 2nd Secondary coil & effects

    Hi, We have an induction heater, like a stove top one, not industrial. I want to understand what happens when an additional load is added that it isn't intended to receive. A plate goes on the induction warmer, it gets heated up, then removed and another plate takes it place. What happens if the...
  30. K

    Inducing electricity w/ moving piece of metal, static magnet

    Hi! I'm curious to know, whether it is possible to produce electricity by moving a piece of metal over a magnet (i.e a immobile magnet and a moving piece of metal close to the magnet), and how this would be done in practice.