# Read about magnet | 93 Discussions | Page 2

1. ### I Solutions of wave equation but not Maxwell equations

Maxwell equation in absence of charges and currents are $$\nabla \cdot \bf{E} = 0 \\ \nabla\cdot B=0 \\ \nabla \times E=-\frac{\partial B}{\partial t} \\\nabla \times B=\mu \epsilon \frac{\partial E}{\partial t}$$ Wave equation is \nabla ^2 \bf{E}=\mu \epsilon \frac{\partial^2...
2. ### B Can a magnet have more push force than it weighs?

Simple question. Can a magnet have more push force than the magnet itself weighs. Example: A magnet weighing 2kg having a push force equal to 3kg.
3. ### I How do you calculate the force between two magnetic dipoles?

I've seen a couple of equations on Wikipedia and other sites and all of them are different. I need an equation as I want to specifically calculate the force between a magnet and a steel ball. The equations I've seen is this one here...
4. ### B Magnetism - stability of a ring with a sphere inside it?

Hey, is it possible to have a cylindrical ring (made of permanent magnet) and a magnetic sphere sitting inside it and staying in one place without touching the inner sides of the ring and not falling through? The object doesn't necessarily have to be a sphere. If it would work with any other...
5. ### B Interaction between a neutral atom and an external magnetic field

Lets suppose that I have a magnetic dipole moment at (0,0,0) pointing to the Z axis, and in the position (X,Y,Z) in the space, I have a Hydrogen atom, I would like to know the exact interaction between the magnetic field created by the magnetic dipole moment in (0,0,0) and the magnetic fields of...
6. ### I Forces applied to a leaning levitating bicycle

Hi! So I'm building an electromagnetic bicycle where the frame is levitating over the wheels, thus reducing the rolling friction to almost zero by removing the bearings. Magnets have also been placed alongside the wheels to provide side to side stability. Black is the frame, red are the magnets...
7. ### Pipe or coil in generators

Hi, I understand you can induce an electrical current by passing a magnet through a copper pipe. If so, why do generators (and motors for that matter) use coils in stead? Do coils allow a stronger current or greater efficiency? Where can I go to find out the most energy-efficient design for a...
8. ### Solenoid force calculation

Hello everyone, So for a personal project I want to calculate the force necessary for a solenoid (electromagnetic coil) to keep a permanent magnet triangle locked diagonally up and down at the same time so that it does not move in any direction. I need to know the values for coil thickness...
9. ### I Magnet clamp repelling in coil

I have a practical question. I want to make a rubber (silicone) hose/plug that is pinched closed by two magnets ( very strong magnets such as ones from a hard drive the Neodymium kind). I want to place then into a coil and when I want the liquid to flow, I want to turn on the coil and have the...
10. ### Metal: no attraction to magnet and block magnetic fields?

Hi, Can anyone help me in finding out a Diamagnetic or Paramagnetism or Ferromagnetism or any other metal which has following capabilities: 1- Should not be attractive towards magnet. 2- Should not allow magnetic fields to pass through inside. Thanks! THG
11. ### I Ballistic Lenz's Law

If a magnet was going fast enough as it approached/entered a copper tube, could the current induced in the tube via Lenz's Law be high enough to melt or even vaporize the tube?
12. ### B Does a moving bar magnet create charges?

So I understand that a charged particle moving relative to me has a magnetic field, and does not have one if its stationary relative to me... So is it true that a magnet moving relative to me has a charge? Say I took a bar magnet and threw it away from me way out in space, would it acquire a...
13. ### Magnet Fundamentals and Iron Powder

I am creating a product that incorporates magnetic sensing of magnetic nanoparticles. However due to their cost, I have decided to search for other avenues of testing. My question is about whether Iron Powder will retain a magnetic field once magnetized. I basically will place some iron powder...
14. ### I Inhibit repulsion between two like poles

Please excuse the lay terms that will follow. I have been doing some reading on "magnetic shielding" and have come across alloys such as MuMetal which have high permeability and so can block interaction between two magnets. My question; Is this inhibition of interaction between the two...
15. ### I Is there energy associated with flux pinning?

This is probably a very naive question, but I am trying to wrap my head around the concept of flux pinning (quantum locking). For all intents and purposes, it appears as if a superconductor suspended above a magnetic field is defying gravity. I understand that there is no work being done (as...
16. ### B Rigorous definition of magnetic poles?

Hi. Since there haven't been observed magnetic monopoles so far, what exactly do we mean when we talk about the north/south pole of a magnet? Is it something like "north is where the field lines exit a solid body" and "south is where they enter" or is there a more rigorous definition?
17. ### Writing: Input Wanted A Magic Compass & Real Magnetism

Hello! I'm looking for some help regarding magnetism and how it might work (or be fictionalized) in regards to a "magic" compass. I have two questions. Please excuse my complete scientific ignorance :) In my story, our young hero has a compass. The compass needle just spins in endless...
18. ### B Magnetic field strength over distance

I want to know how does distance affect the magnetic field of a permanent magnet. I have read about the inverse square law and how it could apply to magnetic fields over growing distances, but doing so, I read about monopoles, which is a new concept to me. So, for the time being, I would like a...
19. ### B Small powerful electro magnet

Hello, i need a small electro magnet with it's dimension not bigger than 8 millimetre (0,31 inch) in diameter with a length under 10 millimetre (0,39 inch). I want it to be as powerful as possible, where do i find such magnets? And how should i make my own? How powerful is it possible to make...
20. ### I How does a magnetizer/demagnetizer work?

Hi. These things can be used to magnetize/demagnetize tools, e.g. screwdrivers: How do they work? I'm particularly interested in the demagnetizer part. How do the field lines look like? And why is there this stair-like structure in the upper hole?
21. ### A Theoretical Magnetic Propulsion

I was curious to the effects of a strong electromagnetic field applied to an object at distance. The field must be able to quickly activate and deactivate in order to account for the distance traveled towards the object as to eliminate the force applied to the source of the field by the object...
22. ### I Distance and material affects on magnetic full strength

Hi Folks: This is my first post, I hope that I observing the proper etiquette. If I have a magnet with a known pull strength is there a way for me to determine the affect of 1/4 inch plywood on the magnets pull strength when the plywood is placed between the magnet and the surface metal? Thank...
23. ### How do you magnetize a circular magnet?

< Mentor Note -- thread moved from New Member Introduction Forum > Hello, this is actually my first post on Physics Forums (I just joined) The question above is the one that I thought that would grab the most attention. I actually have 3 questions concerning magnets... I require a special...
24. ### A Can a demagnetized neodymium magnet be restored?

Can a Neodymium magnet get back it's magnetic properties after being demangnetized? Say that there is a Neodymium magnet(Nd-Fe-B) that has been demagnetized(turned paramagnetic) at a temperature higher than its curie temperature. If I extract the demagnetized Neodymium(Nd) from the...
25. ### Distance variation dependency between coil and magnet

Hello! I'm wondering if there's a general dependency/connection/correlation/function for changes in distance between an electromagnet (coil with iron core) and a magnet (Samarium Cobalt). Here's a picture to explain what I mean: If I move the coil closer to the magnet (smaller x) the force...
26. ### Magnetic Induction

Homework Statement Homework Equations I am not really good at this topic, but I think you would need both the right hand rules (one that involves finding direction of current via magnetic field as well as the one for finding magnetic force) The Attempt at a Solution So I drew out magnetic...
27. ### B Estimating magnetic field based on pull force

I am trying estimate the approximate value in gauss of the magnetic field of a magnet I have based on its pull force, and I am wondering if anyone can comment on the validity of my method. I have tested the pull force of my magnet by weighing the heaviest object it can hold. I have also found...
28. ### B Gaussian gun: Where does the extra kinetic energy come from?

Probably a stupid question, but I do not get it... Here you can see an experiment demonstrating the Gaussian gun: Here I understand how momentum is conserved, i.e. the smaller mass of the ejected ball times its high speed is equal the bigger total mass of the recoiling masses times its...
29. ### How does a square shaped magnet act like a ring magnet?

Hi, I'm working with a magnetic levitron project and I've borrowed a professional levitron to see how it works. When I remove the back cap, unexpectedly I saw a square shaped magnet instead of ring magnet. But it acts like almost a ring magnet. I'll explain the difference with images below. At...
30. ### Does a photo-resistor create an AC current?

I'm a high school physics student. I want to do an experiment to see what happens when a high frequency alternating current goes through a magnet. To create the high frequency alternating current could a photo resistor do that for me? Does the photo-resistor create an alternating current with a...