What is Magnetics: Definition and 56 Discussions

Magnetism is a class of physical attributes that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. Magnetism is one aspect of the combined phenomenon of electromagnetism. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Demagnetizing a magnet is also possible. Only a few substances are ferromagnetic; the most common ones are iron, cobalt and nickel and their alloys. The rare-earth metals neodymium and samarium are less common examples. The prefix ferro- refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4.
All substances exhibit some type of magnetism. Magnetic materials are classified according to their bulk susceptibility. Ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, but there are actually several types of magnetism. Paramagnetic substances, such as aluminum and oxygen, are weakly attracted to an applied magnetic field; diamagnetic substances, such as copper and carbon, are weakly repelled; while antiferromagnetic materials, such as chromium and spin glasses, have a more complex relationship with a magnetic field. The force of a magnet on paramagnetic, diamagnetic, and antiferromagnetic materials is usually too weak to be felt and can be detected only by laboratory instruments, so in everyday life, these substances are often described as non-magnetic.
The magnetic state (or magnetic phase) of a material depends on temperature, pressure, and the applied magnetic field. A material may exhibit more than one form of magnetism as these variables change.
The strength of a magnetic field almost always decreases with distance, though the exact mathematical relationship between strength and distance varies. Different configurations of magnetic moments and electric currents can result in complicated magnetic fields.
Only magnetic dipoles have been observed, although some theories predict the existence of magnetic monopoles.

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  1. abrek

    B Possible movement of this magnet?

    If we take a surface with a strong negatively charged field and place a magnet in it in a specified position so that it does not change its angle, will the magnet be repelled and move to the side?
  2. C

    Magnetic Force in Parallel Magnet Setup: Exploring the Strength of Attraction

    Imagine two parallel lines of five magnets each, spaced a few millimeters apart. In the first line, all magnets have their north poles facing one direction. In the second line, each magnet's south pole faces the corresponding north pole of the first line, but the magnets are offset by one along...
  3. K

    Magnetics Question; is the Answer Really as Obious as it Might Seem?

    We have an ideal electrical transformer, 1:1 turns ratio. We can ignore winding resistance, core losses, hysteresis, core saturation, etc. Call the primary P and the secondary S. The secondary is connected to a programmable voltage generator and to a resistance R in a simple series circuit...
  4. hiddenname

    I Electricity & Planetary Magnetic Field Reversal: Implications & Studies

    What is/are the potential or theoretical effect on electricity due to reversal of planetary magnetic field? Would circuitry continue to function or would knowledge and understanding need re-evaluating as a result of a reversal of our magnetic field on planet Earth? Note: this is not a homework...
  5. N

    Lenz's Law for a rotating PM motor rotor spinning in a thin CU tube

    The motor is required to operate at its resonance frequency and I am looking to add a thin-walled (0.010") copper tube inside the stator bore to add some damping. The current motor air-gap is 0.015". If I install a copper tube in the stator bore bonded to the stator and leave a 0.005" air-gap...
  6. TheBigDig

    Force on a magnet in a magnetic field

    So I'm kinda stumped. I'm assuming that since ##\vec{m}||\vec{B}##, the x and y components of both are zero. But I'm unsure how to take this further.
  7. C

    Imperial-Metric Unit conversion for Magnetic Field Gradiometer?

    Hi all, I have a question which I think should be a simple solve for most people but I cannot seem to get my head around it. It is a common case in geophysical surveying that a magnetic field vertical gradiometer might be used. This instrument uses two magnetometers separated by a known...
  8. MReX19985

    Is it possible to create weightless rotors using magnetic fields?

    Hello I had an idea a while ago If we have an electric motor with 8 poles where all poles are the same (north or south) 360 degree And rotor is iron core which can have eddy current What came in my mind is the rotor will be wightless but don't know what will happen Perfect use of this idea is...
  9. kyphysics

    What's w/ the news of Earth's magnetics poles about to flip?

    Anyone else seen lots of recent news articles on this? Is it as scary as some portray?
  10. J

    Coupled inductor boost converter - Ripple current

    I am trying to calculate the ripple current in boost converter for ∆i1 and ∆i2 between time intervals between DT and T, and also dependent on the voltage level (Vin or Vin-Vout). To find a formula for ∆i1 and ∆i2, two formulas have to be derived for them. This is done from the equation: I...
  11. M

    Fun magnetics question with the Meissner Effect

    I was hoping I could get some help deriving a formula that shows how much current is needed to generate enough of a magnetic field to lift an X Newton mass L meters above a superconductor. ( Probably in centimeters but meters here for the sake of SI easiness ) I was helping one of my professors...
  12. person123

    Magnetic Gears For Power Transmission

    This thread is an attempt to better understand the pseudo direct drive, or PDD, gear. What I do know is it's made up of a set of magnets which can serve the function of a reducer- a basic diagram of it as well as a video can be seen below. In this mechanism, the inner rotor is the input while...
  13. F

    Load line analysis in femm4.2

    Dear Forumers, This question is about load-line analysis for loudspeaker driver magnetic circuits in FEMM 4.2 (Finite Element Method for Magnetics), I can't seem to get an answer from the mailing lists. I would like to get the permeance coefficient for random points inside the magnet. I have...
  14. Z

    Finding the magnetic field of a wave from the E field

    Homework Statement Many sources of electromagnetic waves (stars and light bulbs, for example) radiate in all directions. A simple example of the electric field for a monochromatic electromagnetic wave produced by a spherical source is $$E(r,\theta,\phi,t)=A\frac{\sin \theta}{r} \big(\cos...
  15. K

    What are the unanswered questions in materials science and high energy physics?

    Hi, I love learning, and from time to time I run into questions that google, local education institutes, and general information hunting at the library comes up fruitless. So to you physics forum I turn! About me - Father, husband, geek, techie, cancer survivor x2, retired soldier/IT...
  16. cnh1995

    DC Machine Magnetics: Torque, Back EMF & Flux Explained

    I have a question regarding this part from a book on electrical machinery (the author is highly reputed in India). While teaching the motor action at an elementary level, the torque developed in the motor is explained using the equation F=Bil. But this paragraph says that the torque developed is...
  17. Hanarchist

    Creating a Maglev Track using Electromagnets?

    Hi All, I was wondering how I would go about creating a circular maglev track using electromagnets? The idea is to have more control over it and to eventually write a piece of code that would allow changes in the strength of the magnetic field potentially? I was just wondering how it would work...
  18. V

    A Problem In Electromagnetic Phenomena

    Homework Statement [/B] In a thin rectangular metallic strip a constant current I flows along the positive x-direction, as shown in the figure. The length, width and thickness of the strip are l,w and d, respectively. A uniform magnetic field B is applied on the strip along the positive...
  19. N

    Will ferromagnetic dust retain magnetism in molten aluminum?

    Curie temperature for magnetite is 858 C, for iron 1043 C. Duralumin melting point is about 630 C. Does this mean that if I take a small silicone mold, place a magnet underneath it, add ferromagnetic powder to the mold and then pour molten aluminum in, I will get the aluminum detail with...
  20. T

    Particle Motion in Uniform Electric and Magnetic Fields

    Homework Statement A particle of charge q and mass m is projected on a rough horizontal plane (X-Y) from a point (a,0,0) with initial velocity v = V j . In space there exists uniform electric and magnetic field E k and -B k respectively. Acceleration due to gravity is g and friction coefficient...
  21. S

    Velocity of current-carrying cylinder

    Homework Statement A cylindrical rod of length w carries a current I as shown(perpendicular to B) and is bathed in a field B perpendicular to the plane in which is a " shaped rail. The rod rolls without slipping on the rails, its length perpendicular to the two parallel rails and equal to the...
  22. S

    Capacitor with magnetic dielectric

    Odd question, would anybody know what would happen if a parallel plate capacitor (good conductor) had a soft magnetic material (fairly poor conductor) as a dielectric? What would be the DC/AC electrical characteristics of this?
  23. icecubebeast

    Tips on how to properly study Physics (mechanics and magnetics)

    Hello, Next year I will be taking more than 6 ap classes and I was wondering how to manage my study time and how I study. I will be taking two exams on physics next year (AP Physics C: mechanics and electromagnetism) along with many others. The questions are: 1. How do you find time to study...
  24. J

    What is the best topology for adding surge protection to Ethernet PHY?

    Hi, Guys I have a B78476A8135A003 Magnetic Module from EPCOS and I want to add a surge protector either on the TJ45 connector side or the Ethernet PHY side. I can't decide which way is more beneficial. Here is the topology: Ethernet PHY : B78476A8135A003 : Surge Protector (SLVU2.8-4) ...
  25. J

    Using SPICE with FEMM (Finite Element Method Magnetics)

    Hello All, Some of you may have heard of the freeware FEA program called FEMM written by David Meeker. It is used to simulate 2D electromagnetic geometries and also has an integrated LUA scripting host which allows script files to be written to automate the process. I'm currently using...
  26. E

    Frequency magnetics converting to tesla?

    Hello, For the last 2 months I've been trying to find a relation between a frequency magnetic field and the amount of tesla a coil has to induce. When I found this forum and I thought if somebody can help me it would be you guys. I'm a student at the TU in Delft the Netherlands and I'm...
  27. dexterdev

    Doubt regarding Transit time in electro magnetics

    Hello PF, I was watching a video from NPTEL (transmission lines), where the professor was explaining transit time. Ok now my doubt is that is the transit time delay in transmission lines due to distributed capacitors and inductors alone. Do resistors contribute to delay. For a...
  28. K

    What Are the Differences Between B, H, D, E in Physics and Types of Magnets?

    1-What's the difference in Magenetic between B,H or in electric between D,E? 2-what's permanent magnet and how it differ from electromagnetic pole?
  29. Y

    Understanding Bmax in Magnetics and the Role of Half-Cycles: A Question Analysis

    I don't understand what the book said. See attached page, 1) The Red underlined section. I don't understand why B will be at it's max negative value at the beginning of the cycle assume it is sine wave start at V=0 at t=0. 2) What is the "subsequent half-cycle? Why is it has to be divided...
  30. T

    Challenging Problem Equations of Motion for Spherical Magnetics Pendulum

    Homework Statement I struggle to write equations of motion for spherical magnetic pendulum. The forces acting on the pendulum are: gravity, tension in the rope, and 4 repelling forces Here is the picture for the problem: first attachment (I didn’t add forces to not mess it up) There are...
  31. Y

    Question on simple static magnetics

    Suppose a closed loop with constant current around the loop. The loop is in a uniform constant B field. The force is \vec F=I\left (\oint_c d\vec l\right ) \times \vec B. Being a closed loop \oint_c d\vec l=0. So there is no force acting on the loop. BUT at the same time, we know there...
  32. B

    Finding the Minimum Magnetic Field for Coil Tipping: A Scientific Analysis

    a problem in magnetics... i've been stuck here for long....please help ; a square coil of side A ,carrying a current I ,is placed on a table and a magnetic field B parallel to one of the edges is switched on. the mass of coil is M now the question says-"find min magnetic field for which the...
  33. A

    Contactless dynamo for my road bike - help with the magnetics please

    Hi all, Would appreciate some help with the magnetics in a contactless dynamo I'm trying to build for my road bike to power some LED lights. I've got 8 rare-earth magnets mounted on the bike wheel, near the hub. They're flat, round magnets, around 2cm dia., mounted all the way around the...
  34. M

    What is the Third Spin in Frustrated Magnetics Lattices?

    What is definition of frustrated magnetics lattices?
  35. Y

    Calculating the Mass of a Chlorine Anion Using Electric and Magnetic Fields?

    Homework Statement The mass of an atom can be determined by ionizing it and accelerating it through a known electric field followed by a known magnetic field. The ion’s circular path is then measured. Calculate the mass of a chlorine anion of charge 3.20 x 10^-19 C if it follows a circular...
  36. H

    Need A Finite Element Magnetics Code That Handles Dynamic Modeling

    To the EE Forum, I am a new guy on this Physics Forum and this is my first post. I have downloaded a free software code, Finite Element Method Magnetics (FEMM) solver (see http://www.femm.info/wiki/Download) but it doesn’t work because FEMM is limited to solving low frequency electromagnetic...
  37. A

    Solve Magnetics Project: Calculate Charge of Magnets & Electric Field Strength

    Please be in metric if helping. So Looking on wiki I have found some formula's but not sure on there application of process to be used with the information I have gathered.Homework Statement I have a project in where I need to be able to calculate hopefully the charge of a magnet and its A/m...
  38. V

    Exploring the Electromagnetic Properties of Rodin Coils

    I've been wondering for a while, a Rodin coil's magnetic field generation is the center as a strong open air magnetic field is it unique or is it easily duplicated with different wire configurations that might have this property in a stronger manner more easily. I have tried to find other...
  39. Z

    How Does Angular Velocity Affect Tension in Rotating Charged Rings?

    Homework Statement A charge Q is uniformly distributed on the ring which is free to rotate about a light horizontal rod. The rod is suspended by light inextensible strings and a magnetic field B is applied as shown in the figure. The initial tensions in the strings are To. If the breaking...
  40. A

    Mass of an Atom and magnetics problem

    Homework Statement The mass of an atom can be determined by ionizing it and accelerating it through a known electric field followed by a known magnetic field. The ion’s circular path is then measured. Calculate the mass of a chlorine anion of charge 3.20 x 10-19 C if it follows a circular...
  41. S

    What is Lenz's Law and how does it relate to magnetics?

    Homework Statement http://dl.getdropbox.com/u/119186/Picture%20lenz.png Homework Equations Don't need any! The Attempt at a Solution I know that the first one is A. Loop 1 induces a magnetic field into the Loop2, then using right hand rule you get that it has to be clockwise...
  42. B

    Pumping electrons without magnetics?

    Is it possible to push electrons down a wire if a wheel applying pressure to the wire were rolled down it? Another way to cause the pressure would be to apply a heat source down the wire.
  43. Q

    Magnetics: Exploring the Basics and Beyond

    Hello, I've come to terms that I am fascinated with magnets and how they work. I thought I would come here to ask some questions before I go out start a search on my own. What I know: A magnet is a medal:), It does not attract objects that are not medal. The Earth's core is basically a giant...
  44. B

    Why does the magnetic flux in a CT core decrease with connected load?

    Hi Guys, :smile: I am grappling with a peculier (but somewhat common) problem with Current Transformer (CT) magnetic circuit. I will be very grateful if someone could help me out with my problem. 1)In an ideal Voltage Transformer (VT), the magnetic flux developed in the core remains...
  45. K

    Help clarifying an answer for magnetics question.

    Homework Statement http://www.aijaa.com/img/b/00334/3685081.jpg Homework Equations B= \frac{ \mu _0}{2 \pi r}I The Attempt at a Solution I got it wrong the two first times (I got \frac{ \mu _0I}{2 \pi a}(1- \frac{a}{b})), then the assistant teacher showed how it was done, but wasn't able...
  46. S

    Magnetics of transformers and induction in metals

    If you have the primary and secondary coils of a transformer next to each other, then current will induce a voltage in the secondary coil, creating current flow. This question applies to motors as well. If I place a sheet of steel between the two coils, will I still induce a voltage? For...
  47. C

    Shielding magnetics to prevent interaction

    Could anybody tell me, if there is anything that can distract magnetic field, but not in the way diamagnetics do. I.E. when I put two magnets on table N|S S|N they will start repulsing themselves, and i want to know, what can i put between them, to avoid reaction of repulsing, so there will be...
  48. L

    Understanding Magnetic Attraction: Non-Magnetic Metal and Poles Explained

    How does a non-magnetic piece of metal have an attraction to only one of the poles when you put it near a magnet (it tries to flip to the opposite side)?
  49. T

    Calculating the Radius of a Charged Ion's Path in a Magnetic Field

    Here is the problem: A singly charged positive ion has a mass of 2.50 X 10 ^-26 kg. After being accelerated through a potential difference of 250 V, the ion enters a magnetic field of 0.500 T, in a direction perpendicular to the field. Calculate the radius of the path of the ion in the field...
  50. Amith2006

    Electromagnetics: Electric Field from Conductor?

    Sir, When a current is passed through a conductor, a magnetic field is produced around it. Due to the flowing charges, is an electric field also produced around the conductor?