Magnetism Definition and 974 Threads

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. L

    Magnetism, electrical and thermal conductivity of metals

    1. I would like to test myself on how well I know my information about certain metals, some of them get me a bit puzzled. How would you rate the electrical conductivity of cast iron? Poor, good, excellent or best? Also the thermal conductivity of 304 stainless steel? Poor, good, excellent or...
  2. L

    Magnetism, electrical and thermal conductivity of metals

    I would like to test myself on how well I know my information about certain metals, some of them get me a bit puzzled. How would you rate the electrical conductivity of cast iron? Poor, good, excellent or best? Also the thermal conductivity of 304 stainless steel? Poor, good, excellent...
  3. bcrowell

    Free edition of Purcell, Electricity and Magnetism

    Thirty years after learning E&M from the wonderful book by Purcell, I noticed that the copyright page of my dog-eared copy of the 1965 edition includes a notice stating that it is available for use by authors and publishers on a royalty-free basis after 1970. The book has gone through two more...
  4. K

    How Is Electricity and Magnetism Used In Computer Science?

    I am a computer science major and we are required to take two semesters of physics. First semester is based on mechanics and the second semester is focused on electricity and magnetism. I was wondering how these topics are used in computer science and in what specific area? I have tried looking...
  5. S

    Magnetic Dipole Moment: Solving Homework Questions

    Homework Statement in the topic related to magnetic dipole moment. The result is derived that m/l = q/2M m= Magnetic Dipole moment of the substance[of mass M whose angular momenta=L] with a charge q Homework Equations Now my question to you is whether this "result"...
  6. D

    Does Work Done by a Spherical Force Field Depend on Path?

    Homework Statement A force eld E has the spherical components Er = (2Dcosθ)/r3 Eθ = (Dsinθ)/r3 E\phi = 0: (a) Evaluate by line integration the work it does in taking a point (parti- cle) from point A in the diagram to point B via the quarter circle r = a; 0 <...
  7. A

    Power & Magnetism: Calculating Resistance & Loss

    If we have a solenoid and a magnetic passes through it , it will produce a dc voltage in the wire . If we want to calculate the power , we find out the current using ohms law then we use P=VI . I know there is power loss due to the resistance ( joule effect) . But what about the opposing...
  8. K

    Exploring the Current Frontiers of Electricity & Magnetism

    So I'm a physics major in my second semester of undergrad physics and have been completely blown away by electricity and magnetism. The stuff just amazes me. So I was wondering what the current hot topics of E&M are. What are the unanswered questions? What kind of things would I be...
  9. U

    Magnetism as a Relativistic Phenomenon

    Consider a wire with charges moving with speed 'v'and '-v' in frame F (with charge q at distance s away moving at speed u). In frame F', the charge q is stationary, and so the speeds of the charges in the wire are v+ and v-, where v- > v+ Hi guys, I have trouble following through the proof in...
  10. T

    Relationship electricity and magnetism

    Hello, I have started reading a beginners book (from the "stop faking it" series) on electricity and magnetism. Its supplied with funny little experiments to help me understand the topic. But I have trouble understanding the intimate relationship between electricity and magnetism. I believe I...
  11. P

    Analogy for magnetism in the nuclear strong force?

    Whenever people begin to explain the nuclear strong force, they relate it to electricity. I was wondering if color charges, besides also interacting with one another in a way that's analogous to electricity, can also interact in a way that's analogous to magnetism. I have asked some professors...
  12. R

    Calculating Magnetic Field in a Circular Circuit with Varying Resistivity

    Homework Statement In the ATTACHMENT is the given circuit. Which contains two resistance R1 and R2 in form of circle of radius r = 1 m with a battery having e.m.f. V = 10∏ volt. Upper resistance is having resistivity = 4Ω-m & lower resistance having resistivity = 2Ω-m. Angle between two...
  13. Q

    Electron configuration, magnetism, and unpaired electrons

    My answer key claims it's answer E. I don't think it's right; I think it's cobalt with three unpaired electrons. Not four. A 3d7 configuration, through the Aufbau principle, would fill two of the five d electron pairs completely and leave three half filled. This works mean it's also para...
  14. Newtons Apple

    Exploring the Significance of Coils in Electricity and Magnetism

    hey everyone, I have a questions, that is very general, and perhaps, silly... but why are coils so significant in terms of electricity and magnetic fields? why is it when you push a magnet through a coil, you get a charge, but not when you touch it to a straight copper pipe? Or when you see...
  15. Y

    Simple Conceptual True/False Questions About Magnetism

    Homework Statement 1). Magnetic Field lines begin and end at magnetic charges. (True or False) 2). Magnetic field lines are "lines of force" for charged particles. (For example, a charge will follow the magnetic field lines.) Homework Equations The Attempt at a Solution I...
  16. C

    Induction, magnetism (flux), and current

    Hi, inductance is the property of a conductor by which a change in current in the conductor "induces" (creates) a voltage (electromotive force) in both the conductor itself (self-inductance). --wikipedia From what I understand, the inducing happens due to the resulting change in magnetic field...
  17. T

    Why is the attractive force if magnetism not accelerative?

    If i put something from space to Earth it accelerates at a rate of 9.8m/s2, why is it so? Does acceleration happens in attraction between two magnetic poles? If so what is its rate?
  18. B

    Understanding Magnets: How They Work and Their Importance in Flux Lines

    i am very confused by the idea of magnets how do magnets attract things ? and if they do attract things , then what is the importance of flux lines ? i mean , shouldn't magnets just align things to the flux lines in the direction of the north pole ? i want to know how magnets work in...
  19. adjacent

    Where Does Kinetic Energy for Magnetism Come From?

    If, -There is an iron rod.(It does not have magnetic potential energy at this time) -I made an electromagnet in a far away place. -When I bring the magnet closer to the iron rod,the iron rod suddenly gets kinetic energy.Why? As energy cannot be created,from where does the kinetic energy...
  20. M

    Which Physics Book on Electricity and Magnetism Explains Concepts in Vectors?

    Can someone recommend a physics book on electricity and magnetism? The book that I just finished reading for my class was https://www.amazon.com/dp/0971313458/?tag=pfamazon01-20 The book above hardley mentioned vectors and I am looking for a book that explains all the concepts in terms of...
  21. ryanuser

    What Drives the Existence of Magnetism?

    Hi, I am 15 and I got interested in this question. My question is not how magnetism exists, it is WHY magnetism exists? Thanks
  22. E

    Questions related to magnetism

    I'm studying magnetism from my textbook, and I have several doubts. 1. Magnetic flux in my textbook is defined as the number of magnetic field lines passing through a surface held perpendicular to the lines. However, the unit given is Weber- N.m/A How do 'no. of magnetic field lines' connect...
  23. S

    Mermin-Wagner theorem and 2D magnetism

    I am a little confused about the Mermin-Wagner theorem, and the assumptions it makes, and I would like to better understand the 'exceptions' to the rule that occur in practical (non-ideal) scenarios. As is my understanding, The Mermin-Wagner theorem states that there cannot be spontaneous...
  24. S

    What Are the Answers to These Magnetism Questions?

    Homework Statement Please see attachments. Homework Equations F=ILB The Attempt at a Solution F1 - F2 = FT = 5*10^-5 Second one no clue.
  25. M

    Magnetism and Electromagnetism

    In basic but precise terms, can someone please explain to me the fundamentals on how/why these things operate? I've been reading about how these things work but I really want a good understanding on why these works too. Thanks :)
  26. A

    Understanding magnetism and electromagnetism

    Natural Magnets: How do they work? I'd prefer a technical answer on a subatomic level. Electromagnets: Say you have a copper wire hooked up to a negative terminal and on the other end of the wire a positive terminal. Due to a potential difference, electrons flow from the negative to the...
  27. K

    Schools Why do the collegeboard offer Electricity and Magnetism?

    If a prerequisite for E&M is Multivariable calculus, why is it offered in high school (without that pre-req)? Is the High School E&M equivalent to physics 2 in college, and if that is so, Physics 2 is still offered before Multivariate calculus. Can someone clear this up for me. Am I getting two...
  28. T

    Calculate the net force on square loop (Magnetism)

    Homework Statement A square loop of wire of side length L lies in the xy-plane, with its center at the origin and its sides parallel to the x- and y- axes. It carries a current i, in a counterclockwise direction, as viewed looking down the z-axis from the positive direction. The loop is in...
  29. M

    A question about the fundamentality of magnetism

    I'm sorry if I may be asking an unanswerable question here, but I've looked all through the forums and the internet to find a satisfying answer to why moving electric charges create a magnetic field. I'm not trying to ask why electrical attraction/repulsion exists, as I take that as a...
  30. C

    How Do Electron Spins Influence Magnetism?

    1 - How does an electron's spin generate its own magnetic field? 2 - Why are only the orientations of electrons taken into account in statements such as "permanent magnets are created when the orientations of the spin of the electrons are orientated in the same direction" when protons also have...
  31. K

    Medical Do neurons communicate with magnetism ?

    Magnetic effects on the brain are well known, as are magnetic brain scans, but I'm having difficulty finding anything to say magnetism has a function within the brain. I can find electrical communication, but not magnetic. Am I missing something ? Folk, do say if so.
  32. B

    How Hard Is Physics II: Electricity, And Magnetism?

    So I am taking Physics II this fall semester. I am an engineering major, and I am currently split between mechanical, and civil. My questions is how hard will the class be for me? I have already done the three semesters of calculus including a vector calculus extension. I got an A in calc III...
  33. S

    Calculating Particle Mass Using Magnetic Force

    Hey yall: So I ran across this confusing question and was wondering if you guys could help me out. Consider the fact that you have a positive particle (which would be q=1.6E-19) that is traveling at 1.9E4 m/s perpendicular to a 1.0 x 10-3 T magnetic field. If the radius is .40m what is the...
  34. L

    Ligand field theory and f orbitals in magnetism

    I've been introduced to ligand-field theory lately and was then wondering what roles f orbitals play in the magnetic properties of elements and alloys. Apparently f orbitals behave oddly in that they hybridize in weird ways because they're so large and that the crystal field actually affects the...
  35. N

    How Does Electric Field Influence Ion's Cycloidal Motion in a Magnetic Field?

    Homework Statement The figure shows the path of a positive ion moving in the xy plane. There is a uniform magnetic field of 6000 gauss in the z direction. Each period of the ion's cycloidal motion is completed in 1 microsecond. What is the magnitude and the direction of the electric field that...
  36. C

    Physics Magnetism: Ring Behavior When Switch is Closed

    Homework Statement http://upload.lsforum.net/users/public/c7843Untitleda235.jpg when the switch is closed what happen to the golden ring when the switch is closed? explain the switch remains closed. what happen to the ring if the slide contact of the rheostat i) is kept at A ii) moves from A...
  37. G

    Magnetism of a bar magnet - maximum rate of change?

    Magnetism of a bar magnet -- maximum rate of change? If a bar magnet is placed along the x-axis with (0,0) at its center, along which axis does the magnetic field fall off faster and why?
  38. S

    Calculating Magnetic Forces on Moving Charges in a Magnetic Field

    Homework Statement 1. Determine the magnetic force acting on an proton (m = 1.67 x 10-27 kg) moving at 2.9 x 106 m/s in a magnetic field of 6.8 T. The proton is moving south. The magnetic field points straight down. 2. A 6.0 m long wire with 7.0A of current flowing through it experiences a...
  39. S

    Magnetism; the path of electrons

    The path of electrons emerging grom an accelerator must be bent by 90° by a 'bending magnet' so as not to strike a barrier in their path a distance d from their exit hole in the accelerator. Show that the field B in de bending magnet, which we assume is uniform and can extend over an area d*d...
  40. F

    Faraday's law and gauss's law for magnetism apparent contradiction

    I was reading here https://www.physicsforums.com/library.php?do=view_item&itemid=294 gauss law's for magnetism says ∮B⋅dA = 0 but then faraday's law has d/dt ∮B⋅dA in it. Well if its 0 then d/dt of 0 is 0.
  41. T

    Magnetic Deflection of an Electron on Earth's Equator at 1000m Altitude

    Homework Statement Question: An electron is located on the Earth's magnetic equator at an altitude of 1000m. In which diretion will it be deflected when it is projeted upward? Homework Equations Not sure The Attempt at a Solution I'm trying to study for an electromagnetism exam trying...
  42. A

    Understanding Static Magnetism: How Does it Work?

    Maybe a stupid question, but I'm trying to get my brain around the concept of magnetism, specifically for static magnets, not electromagnets. I understand that the magnetic field is a result of all the moments in the atoms being aligned. The spin of the electrons around the atoms is the current...
  43. D

    Electricity & magnetism, circuit with capacitors

    https://www.dropbox.com/s/gvml20bk7435zoa/a.gif I need to calculate the equivalent capacitance of this circuit, but I cannot tell which of the capacitors are in series or in parallel. Can someone explain to me how can we figure this out?
  44. A

    Magnetism and Magnetic Fields- Determining mass of ion

    Homework Statement An ion of mass m and charge q is accelerated from rest through a voltage of ΔV. It then enters a magnetic field. Determine the mass of the ion in terms of the measurable quantities: q, ΔV, (B^→) , and x. Homework Equations The Attempt at a Solution m =...
  45. C

    Conceptual questions about magnetism

    Do any celestial bodies not have magnetic fields? Why? I'm having a difficult time finding good resources for dynamo theory a question about that... So first what I know: 1 - The Sun has a nonmetal hydrogen/helium plasma interior which is generating a magnetic field 2 - the Earth has a...
  46. C

    How is the Earth's magnetic field generated and maintained?

    Do any celestial bodies not have magnetic fields? Why? I'm having a difficult time finding good resources for dynamo theory a question about that... So first what I know: 1 - The Sun has a nonmetal hydrogen/helium plasma interior which is generating a magnetic field 2 - the Earth has a...
  47. A

    Gravity & Magnetism: How Mass Interacts with Space-Time?

    This may seem really elementary or just based on total misconception but can you not explain any pulling force at distances in terms of relative space and time coordinates instead? Gravity before Einstein: property intrinsic to mass; masses pull each other. ...after Einstein: property...
  48. WannabeNewton

    Simple question on Gravito - Magnetism inside Shell

    Hello there! I have a question regarding the behavior of test particles inside a slowly rotating thin spherical shell of matter under the influence of the gravito - magnetic "lorentz force" (this is all in the weak field slow motion approximation). I want to see just how analogous I can claim...
  49. H

    Gravity & Magnetism: Does it Affect Electrical Charges & Coils?

    My physics sucks but does gravity affect electical charges inside devices... Does it affect magnetism in coils... I thought it has an affect on anything regardless of how small it is.. right?
  50. T

    Looking for more information on magnetism.

    Hello all. I was wondering if anyone know of a website where I can learn more about magnetism? Nothing in particular, I just wanted to know as much as I can on the topic. I have a huge interest in this topic and hate spending so much time looking online only to find bits and pieces. Please...
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