In electromagnetism, there are two kinds of dipoles:
An electric dipole deals with the separation of the positive and negative charges found in any electromagnetic system. A simple example of this system is a pair of electric charges of equal magnitude but opposite sign separated by some typically small distance. (A permanent electric dipole is called an electret.)
A magnetic dipole is the closed circulation of an electric current system. A simple example is a single loop of wire with constant current through it. A bar magnet is an example of a magnet with a permanent magnetic dipole moment.Dipoles, whether electric or magnetic, can be characterized by their dipole moment, a vector quantity. For the simple electric dipole, the electric dipole moment points from the negative charge towards the positive charge, and has a magnitude equal to the strength of each charge times the separation between the charges. (To be precise: for the definition of the dipole moment, one should always consider the "dipole limit", where, for example, the distance of the generating charges should converge to 0 while simultaneously, the charge strength should diverge to infinity in such a way that the product remains a positive constant.)
For the magnetic (dipole) current loop, the magnetic dipole moment points through the loop (according to the right hand grip rule), with a magnitude equal to the current in the loop times the area of the loop.
Similar to magnetic current loops, the electron particle and some other fundamental particles have magnetic dipole moments, as an electron generates a magnetic field identical to that generated by a very small current loop. However, an electron's magnetic dipole moment is not due to a current loop, but to an intrinsic property of the electron. The electron may also have an electric dipole moment though such has yet to be observed (see electron electric dipole moment).
A permanent magnet, such as a bar magnet, owes its magnetism to the intrinsic magnetic dipole moment of the electron. The two ends of a bar magnet are referred to as poles—not to be confused with monopoles, see Classification below)—and may be labeled "north" and "south". In terms of the Earth's magnetic field, they are respectively "north-seeking" and "south-seeking" poles: if the magnet were freely suspended in the Earth's magnetic field, the north-seeking pole would point towards the north and the south-seeking pole would point towards the south. The dipole moment of the bar magnet points from its magnetic south to its magnetic north pole. In a magnetic compass, the north pole of a bar magnet points north. However, that means that Earth's geomagnetic north pole is the south pole (south-seeking pole) of its dipole moment and vice versa.
The only known mechanisms for the creation of magnetic dipoles are by current loops or quantum-mechanical spin since the existence of magnetic monopoles has never been experimentally demonstrated.
The term comes from the Greek δίς (dis), "twice" and πόλος (polos), "axis".
Homework Statement
An electric dipole moment, vector P, is initially pointing in the directio of a uniform electric field, vector E (say, in the positive x direction). How much external work is needed to turn the dipole by 90 degrees?
Homework Equations
vector P is directly...
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)??
I am wondering if there is a source of the magniude of the Dipole moments of all the planets and the sun, m.
m(earth) is 8*10^22 A*m^2.
The Magnetic Field and the Electric Field such that:
Br = Mu0/4/pi*2*m*cos(Theta)/r^3
Btheta = Mu0/4/pi*m*sin(Theta)/r^3
Mphi = 0
Er =...
I have a very basic beginners question in physics and was wondering where to post it.
The post is going to be:
TITLE
What is the difference between an electric dipole and a capacitor ?
I am a trying to understand the difference between an electric dipole and a capacitor. The wikipedia...
Homework Statement
what is the potential 18 cm from a dipole moment 2.6nCm at
a) 42 deg to axis
b) on the perpendicular bisector
note: dipole separation << 18cm
Homework Equations
electric dipole moment, p = qd where q is charge, d is distance
electric potential for point...
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}...
Let's say that the oscillation of a dipole polarization is given by: x(t)=u\cos\omega t - \nu\cos\omega . The driving field is given by E(t) = E\cos\omega t. (u and nu are the in-phase and out-of-phase components, respectively)
So, the time average power is P_{avg} = \frac{1}{2}eE\omega\nu
and...
Hi,
Is dipole operator symmetric or antisimmetric? Or, in other words, do the transition dipole moments from state 1 to the state 2, and from the state 2 to the state 1 have different sign? I.e.
mu_12 = - mu_21.
As far as I understand, the diagonal elements for the dipole operator...
there is a +q and -q on the x-axis. the +q is L/2 in the negative direction and the -q is L/2 in the positive directions. the distance between the two charges is L. there is a test charge P on the y-axis a distance r from both charges.
we had to find the electric energy stored in the dipole...
Homework Statement
A needle suspended from a string hangs horizontally. The electrical field at the needle's location is horizontal with magnitude 3.7 x 10^3 N/C
and it's at an angle of 30 degrees with the needle. There is no net electrical force acting on the needle, but the string exerts...
An electric dipole in the x-y plane consists of two opposite charges with magnitudes of 2uC placed 10cm apart. The dipole is placed in an electric field of 10 N/C along the x-axis with a direction of p +45 degrees from the x axis.
1)Determine the magnitude and direction of torque on the dipole...
Currently reading over some lecture notes on Hertzian dipoles and I want to confirm my understanding on why the E-field pattern is donut shaped.
1) The Herztzian (aka. 1/2 wave ) diploe has two terminals attached to a transmission line feeder. The feeder sends RF current into the terminals...
the conservation of energy formula for a dipole
\DeltaK=-\DeltaU
(1/2)Iw^2=-(-qEDcos(theta))
(1/2)Iw^2=qEDcos(theta)
E-field going parallel to the y-axis. if the positive end of the dipole was in the first quad with angle theta from the y-axis and the negative end of the dipole was in the third...
Homework Statement
A rod of length 2L lies on the x axis, centered at the origen, and carries a line charge
density given by t=T(x/L), where T is a constant. (a) Find an expression for the electric
field strength at points on the x axis, for x>L (b) Show that for x>>L, your result has...
Hi,
I am aware that the effects of a dielectric sphere in a uniform electric field have been done in many introductory electromagnetism books.
Is anyone ware of a similar problem where the uniform electric field is replaced by a dipole field?
Would solving such a problem for the resultant...
Homework Statement
Consider a dipole:
a=50 cm
q1 = +2q on x axis
q2 = -5q on x axis
Point on x-axis where E=0,
Homework Equations
+q1/4pi(eo)x^2 = -q2/4pi(eo)(a-x)^2,
The Attempt at a Solution
algebra =
x= 50/1+ (5/2)^1/2
x = 19.37 cm from +2q
this checks as the...
Hello
Im having 2 questions
I'm investigating NIR light propagation in tissue such as the skin and my question is:
In dipole aprox: Absorption, emission and normal Raman scattering is one-photon processes. But what is Rayleigh scattering?
When light hit a small molecule the dipole...
Why isn't our Local Group's dipole for Microwave Background Radiation pointed towards the center of mass for our Local Supercluster? Clusters are suppose to be just infalling towards gravitational well of it's supercluster. http://en.wikipedia.org/wiki/Cosmic_microwave_background"
See...
Homework Statement
Okay, I totally do not understand how to derive the electric field made by a dipole or a line or a ring or etc.
Homework Equations
When finding the electric field, when you make an estimate, saying that the test charge is very far away, it should be similar to kQ/r^2...
Homework Statement
(Griffith' electrodynamics, problem 3.22): a spherical shell (radius R) carries uniform charge sigma0 on the "northern" hemisphere, –sigma0 on the "southern" one. Find the potential inside and outside the sphere, calculating coefficients explicitly up to A6 and B6...
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...
Homework Statement
assume that two dipoles are placed back -t0 - back along axis as shown:
((-) a (+))(( +) a (-)) ------------------x axisr is oriented between ))(( but above, a distance...
Hello,
This question is more conceptional - I think I can do the algebra (mostly approximations) in this problem ok.
Homework Statement
I am wondering why it is for a radiation zone, that a linear electric quadrupole can be approximated as a dipole. I am wondering if this is...
Homework Statement
Consider two dipoles with moments u1 and u2 arranged as in the following diagram. Each dipole is depicted as two charges of equal magnitude separated by a distance d. The centre-to-centre separation of the two dipoles is the distance r. The line joining the two dipole...
In Hehl's paper "general relativity with spin and torsion:Foundations and prospects",there is a sentence ," in the macrophysical limit, mass (or energy-momentum) adds up because of its monopole character, where as spin , being of dipole character, usually averages out." anybody who know the...
Hi all, I'm kind of confused right now about some concepts.
- Dipoles are essentially point charges of the same magnitude but different signs that are a certain distance away from each other, right?
-In my textbook, they were calculating a charged particle that is on the dipole axis...
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.
1. Problem
Evaluate
\int_{-\infty}^{\infty} \int_{-\infty}^{\infty} \int_{-\infty}^{\infty} z^{2} e^{-A \sqrt{x^{2}+y^{2}+z^{2}}} dxdydz
2. Useful Formulae
none
3. Attempt at Solution
Well, this is part of a much larger problem. I am trying to compute the dipole moment matrix elements...
[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...
[SOLVED] Griffiths dipole moment
Homework Statement
On page 244 of Griffiths E and M book, Griffiths defines the magnetic dipole moment as
\vec{m} = I \int d\vec{a} . Then in problem 5.58, he asks us to calculate the dipole moment of a uniformly charged spinning solid sphere. How is that...
Homework Statement
An electric dipole is located at a certain distance from a grounded plane. What force does the dipole exert on the plane?
(The answer is to be expressed as an equation. No data were given, only the above text)
Homework Equations
I am not sure about this, but the course is...
Homework Statement
A detector hjaving a radius 10 cm is placed 1 m away from an electric dipole. What fraction of total solid angle does the detector cover and what fraction of total dipole power does it detect (assuming 100% detection efficiency)
2. The attempt at a solution
I drew the...
[SOLVED] Pure/Physical Dipole?
Hi,
In the Griffith's book page 154 is two pictures showing pure and physical dipoles. It also writes about these in previous pages but i do not get the point! i mean what is the big deal in the difference between them? Why should Griffith's pay this much...
[SOLVED] Griffiths torque on a dipole
Homework Statement
This question refers to Griffiths E and M book.
In the sentence after equation 4.5, Griffiths says the following:
"For a perfect dipole of infinitesimal length, Eq 4.4 gives the torque about the center of the dipole..."
What is...
1. 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
2. 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?
3...
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...
[SOLVED] Electric Dipole
Homework Statement
I have an carbon atom polarized so it is essentially a physical dipole. I know the spacing between the "two charges" and I know what the charges are. I need to determine the potential difference across the polarized atom.
Homework Equations...
Homework Statement
Homework Equations
The Attempt at a Solution
I am not sure what to do with the -4q.(did something with this)
I was thinking of ignoring it, and treating it like if it is really far away, however since it is only twice the distance from the origin as the two +q charges, i...
Homework Statement
An electric dipole, consisting of charges of magnitude 2.60 nC separated by 7.20 µm, is in an electric field of strength 1400 N/C.
(a) What is the magnitude of the electric dipole moment?
(b) What is the difference in potential energy corresponding to dipole...
I am having some trouble starting this one.
http://img301.imageshack.us/img301/8080/79432817ke4.jpg
Im not sure if I am supposed to replace the psi(v) with some ground state harmonic oscialltor function or not. If so, do I then just take the integrals and then divide 1 to 2 by 0 to 1 to...
Hello people:
Have you ever simulated a dipole antenna in MATLAB, for example, using PDETOOL?
I am trying to achieve this, but I reach to non-accurate solutions when I set non-canonical phantoms in the environment of the dipole, comparing the results with comercial softwares.
This is...
Homework Statement
A dipole sits a distance d above a point charge q which is located at the origin of our coordinate system. In (a) it is aligned in the z direction and in (b) in the y direction. Calculate the energy, force, and torque of the dipole in the field of the charge.
(see...
Homework Statement
In a xy-plane, we have a +q charge in A(0,h) and a -q charge in B(0,-h).
Let's take a field line passing through A, that has horizontal slope in A. Find the point C(m,0) where this field line intersects the X axis.
Homework Equations
I think Gauss' law \epsilon_0...
!dipole!
Okay. So I am trying to do this kind of the old fashioned way. I broke the E's down into x and y component and am adding them together component-wise.
I have found that the x components cancel out. Now I am trying to widdle down the form I have for the y components. As of...
[SOLVED] Electric Field due to a Dipole
Homework Statement
The figure shows two charged particles on an x axis: -q=-3.20(10^{-19})C and q=q=3.20(10^{-19})C. They are both a horizontal distance of 3 m from the y axis. What are the magnitude and direction of the net electric field produced at...
A needle suspended from a string hangs horizontally. The electric field at the needle’s location is horizontal with a magnitude 3.7*103 N/C and is at an angle of 30° with the needle. There is no net electrical force acting on the needle, but the string exerts a torque of 3.7*10-3 to hold the...
Homework Statement
OK I really would appreciate some help on this - just a point in the right direction would be great:
The potential due to the electron in a hydrogen atom at distance r from the nucleus is
V = kq[(exp(-2r/a) - 1)/r + (exp(-2r/a)/a]
Where k=1/(4pie0) where e0 is the...
There is a dipole moment that is symmetric along a y-axis and is along an x-axis. A charge -q is placed a distance a along the -x direction and a charge +q is placed a distance a along the +x direction, making the distance between the 2 charges 2a. I'm supposed to show that the electric field...
An electric dipole p is suspended as a torsion pendulum, which is allowed to pivot
about the nz-axis only. The dipole has moment of inertia I and the torsion spring
has Hooke constant K. In the absence of an electric Field the torsion pendulum's
equilibrium orientation theta-not is equal to...