Magnetic dipole Definition and 125 Threads

A magnetic dipole is the limit of either a closed loop of electric current or a pair of poles as the size of the source is reduced to zero while keeping the magnetic moment constant. It is a magnetic analogue of the electric dipole, but the analogy is not perfect. In particular, a true magnetic monopole, the magnetic analogue of an electric charge, has never been observed in nature. However, magnetic monopole quasiparticles have been observed as emergent properties of certain condensed matter systems. Moreover, one form of magnetic dipole moment is associated with a fundamental quantum property—the spin of elementary particles.
The magnetic field around any magnetic source looks increasingly like the field of a magnetic dipole as the distance from the source increases.

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  1. G

    Question about the magnetic dipole moment of the electron

    Let's say that an electron is moving with constant velocity through a magnetic field. If the magnitude of the field is the same everywhere in space and if it is perpendicular to the velocity of the particle everywhere, the electron will follow a circular path. We all know that. What I need to...
  2. Q

    Does a Rotating Bar Magnet Emit Magnetic Dipole Radiation?

    What is the nature of magnetic dipole radiation? Does a rotating bar magnet give rise to electromagnetic radiation(magnetic dipole radiation to be more specific)??
  3. M

    Magnetic Field of Magnetic Dipole Moment

    I'm seeking some clarification on a topic found in Jackson 'Classical Electrodynamics' Chapter 5. This deals with the magnetic field of a localised current distribution, where the magnetic vector potential is given by \vec{A}(\vec{x}) = \frac{\mu_0}{4\pi}...
  4. R

    Exploring Oxygen's Magnetic Dipole & Radiation Absorption

    How can the magnetic dipole of a molecule (Oxygen for example) affect radiation absorption?
  5. R

    Magnetic dipole in an external magnetic field

    I've run across a diagram that really is driving me crazy. The torque on a mag. dipole should be simply be τ = m X B, where B is the external field as usual. In the image I've attached, there is a large external field, not shown, in the direction of Z which is holding the dipole in the +Z...
  6. S

    Magnetic Dipole Moment - Vector Orientation

    Guys, I don't quite understand the concept of magnetic dipole moment as a vector. Suppose we have a magnet (like a rod) in 3 dimensional space. North pole at (0, 0, 0) and South pole at (0, 1, 0). How would the magnetic dipole vector \vec{m} be oriented? Thanks.
  7. E

    Calculating Magnetic Dipole Moment of a Sphere

    [SOLVED] Griffiths 5.58 Homework Statement A uniformly charged solid sphere of radius R carries a total charge Q, and is set spinning with angular velocity \omega. What is the magnetic dipole moment of the sphere.Homework Equations The Attempt at a Solution The magnetic dipole moment of a...
  8. M

    Magnetic Dipole Moment and Angular momentum

    Homework Statement Show that the magnetic dipole moment M of an electron orbiting a proton nucleus of a hydrogen atom is related to the orbital angular momentum M=(e/2m)L Homework Equations M=NIA, Torque =MB, F=qvB=v^2/r, L=Iw=mrv=rp (where p=mv) N=1 in this case I assume? The...
  9. D

    Force Magnetic Dipole: Electric Current vs Magnetic Pole Model

    There has been some dispute in the past about the validity of the electric current model of a magnetic dipole producing a force \nabla (\vec{m}\cdot\vec{B}) versus the magnetic pole model producing (\vec{m}\cdot \nabla)\vec{B} (see e.g. Boyer `87). I think for elementary particles this dispute...
  10. S

    What is the magnetic dipole moment of the sphere?

    Homework Statement A uniformly charged solid sphere of radius R carries a total charge Q, and is set spinning with angular velocity \omega about the z axis. (a) What is the magnetic dipole moment of the sphere? Homework Equations \vec{m} = I \int d\vec{a} The Attempt at a...
  11. S

    Magnetic dipole in a loop of wire

    This isn't a homework problem, I'm just doing this as practice. Homework Statement A magnetic dipole is oriented in a loop of wire of N turns and radius a so that the dipole vector is parallel to the normal of the loop. The loop is connected to a galvanometer, and the active resistance of...
  12. K

    How can magnetic dipole derivations be solved without using the force equation?

    this is not homework help.I want to know. Hello,can anyone suggest why for a dipole m placed in a magnetic field B F=grad(m.B) and N=mxB?
  13. Amith2006

    Direction of field inside and outside a magnetic dipole

    Homework Statement 1) In the case of a bar magnet, outside it, the magnetic lines of forces start from North Pole and end on South Pole. But inside it, the lines of force start from south and end on North Pole. According to definition of direction of lines of force, it is the direction in...
  14. S

    What is the Magnetic Dipole Moment of a Spinning Spherical Shell?

    Homework Statement Find the magnetic dipole moment of a spherical shell of radiu R carrying a uniform surface charge sigma, set spinning at angular velocity omega. Homework Equations \vec{m} = \frac{1}{2} \int_{S} \vec{r'} \times \vec{K} (\vec{r'}) da' The Attempt at a Solution So...
  15. S

    What is the magnetic dipole moment of a rotating charged record?

    Homework Statement A phonograph record of radius R carrying a unifrom surface charge sigma is rotating at a cosntant angular velocity omega. Find its magnetic dipole momentHomework Equations m = int I \bullet da The Attempt at a Solution Need to find the current first well the sruface charge...
  16. E

    Question: A magnetic dipole m(t) is oscillating

    Hi; Can somebody solve this question below? (i found some answers but I'm not sure of them) TY for your interesting..
  17. siddharth

    Magnetic Dipole Moment of a Surface Current Loop

    For a current loop, the magnetic dipole moment is defined as i \int d\vec{a} Now, if I'm given a surface current 'K', how can I find the magnetic dipole moment? For example, if a disc of surface charge [itex] \sigma [/tex] is rotating with angular velocity [itex] \omega [/tex], what is it's...
  18. A

    Question about a magnetic dipole in an inhomogeneous magnetic field.Please help

    Take the example of a magnetic dipole in a magnetic field. The dipole will experience a torque that will tend to align its magnetic moment with the field lines of the magnet. So why on Earth is there no mention made of this torque in any of the countless descriptions of the Stern Gerlach...
  19. F

    Four potential of magnetic dipole at rest

    I have some trouble with this electromagnetism problem: I need to transform the four-potential of a magnetic dipole at rest, in order to obtain it's value in a reference frame (I understand it's the Lab frame) where we see the dipole moving at v. I know what the magnetic vector potential is...
  20. T

    Magnetic dipole moment homework

    Hello, i have absolutely no clue on how to start this one: a sphere of radius R has a uniform volume charge density \rho. Determine the magnetic dipole moment of the sphere when it rotates as a rigid body with angular velocity \omega about an axis through its center. thanks for the help...
  21. H_man

    Magnetic Dipole Moment does not include the permeability of free space?

    Magnetic Dipole Moment does not include the permeability of free space? Hi, The formula for a magnetic field in a current loop involves the permeability of free space. But the formula for the magnetic dipole moment which seems to represent the flux through a current loop does not...
  22. T

    Deriving the energy of a magnetic dipole in a magnetic field

    For an undergraduate electrodynamics homework problem we were asked to derive the following: (griffiths 6.21) show that the energy of a magnetic dipole in a magnetic field B is given by - U = -m.B where B is the magnetic field and m is the dipole moment. I went about this...
  23. N

    Derivation for Magnetic Dipole of Current Loop

    Hi All, Please show me the derivation of the vector potentiol A for the magnetic dipole. from equation 8.21 to 8.21a This page is taken from Sadikus book. ** i tried all day and couldn't manage to obtain it. i need the derivation step by step ** thanks newbie...
  24. D

    Calculating Energy to Rotate Magnetic Dipole in Solenoid

    i received this problem from my lecturer A solenoid is wound with 2200 turns per meter, and carries a current 2.5A. Take the axis of the solenoid to the solenoid to be parallel to the z-axis. A magnetic dipole moment given (m)=(20A.m^2)i+ (30A.m^2)k is located inside the solenoid. i)how...
  25. S

    Understanding Magnetic Dipole Fields in a Linear Magnetic Sphere

    I need to find the field of a magnetic dipole embedded in the center of a linear magnetic sphere of radius R. My idea was that the field would be identical to that of a superposition of a dipole in a linear magnetic material throughout space and a surface current on the sphere equal to the...
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