What is Magnetic moment: Definition and 181 Discussions

The magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field. Examples of objects that have magnetic moments include: loops of electric current (such as electromagnets), permanent magnets, elementary particles (such as electrons), various molecules, and many astronomical objects (such as many planets, some moons, stars, etc).
More precisely, the term magnetic moment normally refers to a system's magnetic dipole moment, the component of the magnetic moment that can be represented by an equivalent magnetic dipole: a magnetic north and south pole separated by a very small distance. The magnetic dipole component is sufficient for small enough magnets or for large enough distances. Higher-order terms (such as the magnetic quadrupole moment) may be needed in addition to the dipole moment for extended objects.
The magnetic dipole moment of an object is readily defined in terms of the torque that object experiences in a given magnetic field. The same applied magnetic field creates larger torques on objects with larger magnetic moments. The strength (and direction) of this torque depends not only on the magnitude of the magnetic moment but also on its orientation relative to the direction of the magnetic field. The magnetic moment may be considered, therefore, to be a vector. The direction of the magnetic moment points from the south to north pole of the magnet (inside the magnet).
The magnetic field of a magnetic dipole is proportional to its magnetic dipole moment. The dipole component of an object's magnetic field is symmetric about the direction of its magnetic dipole moment, and decreases as the inverse cube of the distance from the object.

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  1. A

    Calculating Electron Magnetic Moment: Spin & Orbital Contributions

    Say I know the total angular momentum of my electron as J. If I write the total magnetic moment as \mu = \gamma J then does \gamma = \gamma_{spin} + \gamma_{orbital} ?
  2. L

    How Accurate Can Magnetic Moments Be Measured with a Torsion Oscillometer?

    Homework Statement The oscillation period of a torsion oscillation magnetometer of T=3s can be measured with an accuracy of 1µs. Let the moment of inertia of the sample and holder have a value of J=10-6kgm2. Evaluate the accuracy with which a small magnetic moment can be determined...
  3. R

    Magnetic Moment, Electron Spin, Energy

    Homework Statement The PE of a magnetic moment in an external magnetic field is given by U = -u dot B. Calculate the difference in energy between the two possible orientations of an electron in a magnetic field B = .6k T Homework Equations The Attempt at a Solution I realize...
  4. J

    Detect variantion of magnetic moment

    hi all, I have to determine if a magnometer is able to detect variation of a magnetic moment. I am given the following observations: n = 2.7* 1021 (number of particles) mu = 2*10-20Am2 detection limit = 10-19 than I am given the variance of the magnetic moment as \sigma^2(m) =...
  5. K

    Is There a More Accurate Equation for the Magnetic Moment of a Solenoid?

    Does anyone have an equation that describes the magnetic moment of a solenoid that does not actually use number of turns as an input? I'm trying to validate a solenoid I have made with something like 11000 turns, but I'm not sure how accurate my number of turns in, so I need a second input...
  6. W

    Magnetic moment of an orbitting charge

    Homework Statement "A particle of charge q is rotating in a circular orbit of radius r[/i with angular velocity [i]w. Determine the magnetic moment associated with the motion of the charge. Homework Equations Q=IT? \vec{\mu}=I\vec{A} The Attempt at a Solution I know how to do it...
  7. M

    Spin, charge, and magnetic moment

    I've read that the properties considered intrinsic to a particle are its mass, spin, and charge. However, unless I am mistaken, both spin and charge can be determined from a particle's magnetic moment. Why are spin and charge considered to be intrinsic instead of magnetic moment then? Sorry...
  8. K

    Measuring Magnetic Moment of a Torque Rod

    Hello everyone, I am working on producing a torque rod (basically a solenoid) for use in a spacecraft that I am working on here at University of Colorado, Boulder. My requirement for this torque rod is to produce at least 7.7Am^2 of magnetic torque. Currently, I have made a torque rod...
  9. S

    Exploring the Magnetic Moment of Point Charges

    why we take electrons as point particles? just because of its magnetic moment? maybe there is something wrong with the idea of the magnetic moment of a point charge. i appreciate if you help.
  10. Y

    Magnetic Moment: What Does It Mean Physically?

    Hi, In one part in my book they define the magnetic moment of a closed loop of current. They define it as \overline{\mu} = I\overline{A} with I the current in the loop and \overline{A} a vector of magnitude the area of the circuit and perpendicular to the current. First I thaught it...
  11. D

    Question - electron mass & magnetic moment

    Can an electron's mass and its magnetic moment be measured in the same experiment?
  12. D

    Understanding Proton Magnetic Moment: Resistance to Change & Acceleration

    This is a question about proton magnetic moment. Does magnetic moment mean moment of inertia, as in resistance to change? Also it seems like this must be measured on an accelerated proton. Is that so, and if so, how is the proton accelerated? Is it a bare proton, or part of a larger system? (I...
  13. D

    Why are there two different values for the electron magnetic moment?

    So far I have found two completely different values of the electron magnetic moment and i need help to know in which cases these are applicable: They both refer (i think) to values of the particle as such, without orbital contribution. Just the spin contribution to the magnetic moment 1st...
  14. A

    Magnetic Moment of a spinning shell

    The problem reads: Find the magnetic moment of a spinning shell of charge Q, radius R, and angular velocity \vec{\omega}. My solution: I split the sphere into infinitely small loops of current (from top to bottom) and add them up. I set my origin on the center of the sphere and...
  15. C

    Magnetic moment is an intrinsic property of elementary particles?

    My question is stated in the title. I wonder is it that scientists are not able to explain the origin of magnetic moment of elementary particles and say that it's an intrinsic property just like mass.
  16. P

    What Determines the Torque and Magnetic Moment in Magnetic Systems?

    when we write \vec \tau=[\vec \mu, \vec B] what is the point or the line about which we are calcuating the torque Also what is the magnetic moment's expression for a surface current and volume current distribution?
  17. P

    What Is the Effective Magnetic Moment in Quantum Mechanics?

    [b]1.I am confused about the topic effective magnetic moment.The equation is U={L(L+1)+4S(S+1)}^(0.5) Where u is effective magnetic moment,. Please clear the various terms and units involved in this. I will be greatly thankful if you could support...
  18. P

    Equation for magnetic moment, E-field and B-field

    Hi! When a charge/current moves in a closed loop, a magnetic moment is generated. Is there any formula for connecting the magnetic moment to E-field and B-field? Patrick
  19. M

    Calculating Field Gradient for Magnetic Beam Deflection

    I feel really stupid that I can't solve this problem, but here goes... The force on a magnetic moment \mu_z in a nonuniform magenetic field B_z is given by F_z=\mu_z \frac{dB_z}{dz} If a beam of silver atoms travels a horizontal distance of 1 m through such a field and each atom has a speed of...
  20. T

    Generalization of the magnetic moment

    I have searched various websites... but all they have about magnetic moments is: \vec\mu=I\vec{A} and \vec\tau=\vec\mu\times\vec{B} but all the the sources only showed that the equation is true for rectangular loop of current. but I need a more satisfactory answer. So I try to prove this in a...
  21. E

    What Evidence Supports the Existence of an Intrinsic Magnetic Moment?

    Hello Everybody, Glad to be back again after a year. My main motivation to be back, is precisely the following observation about the existence of an intrinsic magnetic moment at large scale too. Observations Supporting the Existence of an Intrinsic Magnetic Moment Inside the Central...
  22. I

    How Do You Calculate the Magnetic Moment of a Current Loop?

    I cannot figure out how to solve this problem: The calculation of the magnetic moment of a current loop leads to the line integral (around a closed loop) INT r x dr a) Integrate around the perimeter of a current loop (in the xy plane) and show that the scalar magnitude of this line...
  23. R

    Calculating Induced Magnetic Moment of Steel | Step-by-Step Guide

    Excuse me, can anyone teach me how to calculate the induced magnetic moment of steel, given the applied magnetic field?
  24. fargoth

    Measuring the x magnetic moment

    if L_z|Y_l^m>=m|Y_l^m> whats my possible values for L_x(A|Y_0^0>+B|Y_1^0>+C|Y_2^0>)? i thought id use L_x=\frac{L_++L_-}{2}, create a matrix that would be block diagonal (a block for every l) and then i should find the eigenvalues for every block and say these are the values id get from...
  25. D

    How is sigma subscript (y) related to spin and magnetic moment?

    I don't understand this problem, please help me a) Show that sigma_subscript (y) is Hermitian
  26. J

    Magnetic Moment of 4-Sided Loop?

    Let's say we have a 4-sided loop. Is the magnetic moment different for each side?
  27. E

    Torque, Force, magnetic moment ()

    I'm not sure I know how to start this problem. "A rectangular coil has 16 turns and sides of length a=20 cm and c=50 cm. The coil is pivoted around the y-axis and its plane is at 30 degrees to a magnetic field B=50 k T. The current is 10 A a)Find the force on each side b)what is the...
  28. V

    QED could precisely predict the magnetic moment of electron

    I have a little question about QED.. How come QED could precisely predict the magnetic moment of electron and muon, but can't predict the lifetime of neutron with the same accuracy?
  29. arivero

    Status of neutron magnetic moment?

    I believe to remember some recent comments about the measurement of neutron magnetic moment or some other quantity of this particle, which was not very well in agreement with standard model calculations. I can not remember which measurement it was, or when. Can anyone help my poor neurons?
  30. J

    Magnetic Moment of the Tau Lepton

    Has the value of the Magnetic Momentic of the Tauon been determined experimentally in Units of Joules/Tesla? I have seen these values for the Electron and Muon. Thanks.
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