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".
simple magnetic dipole moment with impossible field lines? clueless.
Hello,
I'm taking a first year university course in electromagnetism. At a certain point we came upon the torque on a current loop in a uniform magnetic field. There we introduced the magnetic dipole moment \overline{\mu} =...
I was reading some topics related to electrostatics where i came across ANGULAR SHM OF A DIPOLE. I could understand everything in SHM. but i can't relate it with electric field. I've some doubts based on the conventions used here... can any1 help me... and this is it... it's given that...
Homework Statement
There are three charges arranged on the z-axis. Charge +Q_2 at the origin, -Q_1 at (0,0,a)
and -Q_1 at (0,0,-a).
Using spherical polar coordinates (i.e the angle \vartheta is between r and the positive z-axis), find the potential at a point with a distance r from the...
Homework Statement
Hi there, I am kind of new to this site, so please bear with me. On the more advanced physics forum page, there was a question about dipole moments, and the way the help had been described was a bit over my head. I am posting this for clarification purposes because this is...
Homework Statement
E-field at (2[m], 30⁰, 90⁰) is E = 4aѳ [V/m]. Find the magnitude and direction of the dipole moment p.
Homework Equations
I know that I need I need to solve for the equation: p = Qd, where Q is the point charge at the given point and the distance between +Q and -Q, which...
As in Feynman's lecture on physics vol 2, he showed that the "true energy" of a magnetic dipole(current loop) in an external B field is m*B, not -m*B. Basically the argument is if you want to pull a current loop from infinity to the final position, you must do extra work to keep the current in...
Firstly, I apologise if this is in the wrong place as it's not a homework question as such, but it is part of coursework.
I am modelling the trapping and cooling of an atom with a laser, and have an equation for the dipole moment which I think may be off. I am getting strange results (slowing...
Homework Statement
A circular coil having 20 turns and a radius of R = 12.8 cm carries a current of 2.70 A. It is placed in a uniform magnetic field of 60.0 mT. The initial angle between the magnetic moment of the coil μ and the magnetic field B is 26.0o.
1)Calculate the magnetic dipole...
May anyone help me with these questions
1 why is a dipole neutral as it completely resembles a system of two charges
2 i know probably its very advanced, but can anyone give me out a scope on wave function and its relation to energy of an orbital
3 am not sure if this is the right forum...
This page contains one derivation for the potential energy:
http://www.shef.ac.uk/physics/teaching/phy205/lecture_4.htm"
Result: U=-pEcos\theta
where
E = magnetic field's magnitude
P = dipole moment = d*Q
d= distance between + and - charge
Q= charges' magnitude
\theta = angle between the...
Homework Statement
..Is it possible to find the Magnetic Dipole Moment of a point particle with spin quantum number 2 and mass equal to that of a proton.
I'm not sure how to start this question as there's nothing on it in the textbooks I have!
Thanks
Hello
The electric dipole potential is
V (\textbf{r}) = \frac{1}{4\pi\epsilon_o} \frac{\textbf{p}\bullet \hat{r} }{r^2}
I am trying to figure out the algebra in my book. How do you evaluate the scalar product of the dipole moment and the unit vector in the above equation?
I get qd...
Hey
have another problem with one of my exercises
Homework Statement
Make a crude estimate for the mean life of an electric dipole transition
in a atom E_\gamma = 10 eV
in a nucleus E_\gamma = 1 MeV
Homework Equations
W_{\alpha \beta} &=& \frac{4}{3} \frac{e^2}{\hbar^4 c^3}...
Homework Statement
The electric dipole moment of a CuSO4 molecule is 3.2 * 10^-32 (i.e. 10 raised to the power of -32)C-m. Find the separation between the copper and sulphate ions.
Homework Equations
Electric deipole moment = 2aq where 2a=separation between the two charges q and -q...
Homework Statement
The problem is: Show that the components of \vec{E} due to a dipole are given at distant points, by Ex=\frac{1}{4\pi\epsilon{o}} \frac{3pxz}{(x^2+z^2)^{5/2}} and Ez=\frac{1}{4\pi\epsilon{o}} \frac{p(2z^2-x^2)}{(x^2+z^2)^(\frac{5}{2})}}...
Homework Statement
The problem is: Show that the components of \vec{E} due to a dipole are given at distant points, by Ex=\frac{1}{4\pi\epsilon{o}} \frac{3pxz}{(x^2+z^2)^{5/2}} and Ez=\frac{1}{4\pi\epsilon{o}} \frac{p(2z^2-x^2)}{(x^2+z^2)^(\frac{5}{2})}}...
Homework Statement
The problem is: Show that the components of \vec{E} due to a dipole are given at distant points, by Ex=\frac{1}{4\pi\epsilon{o}} \frac{3pxz}{(x^2+z^2)^{5/2}} and Ez=\frac{1}{4\pi\epsilon{o}} \frac{p(2z^2-x^2)}{(x^2+z^2)^(5/2)}}...
In Jackson's E&M book, he talks about using the following charge and current densities to demonstrate causality in the coulomb gauge.
\rho (\vec{r},t)=\delta(x)\delta(y)\delta'(z)\delta(t)
\vec{J}(\vec{r},t})=\delta(x)\delta(y)\delta(z)\delta'(t)\hat{z}
since they represent a point dipole...
Homework Statement
Two dipoles are oriented as shown in the diagram below. Each dipole consists of two charges +q and -q, held apart by a rod of length s, and the center of each dipole is a distance d from location A. If q = 6 nC, s = 1 mm, and d = 6 cm, what is the electric field at location...
I am at a loss for how to start this problem.
t = r x F and F = q(E + v x B) i know but there is no external E or B field its just a dipole that moves with a speed v in the x direction the dipole is oriented with +q at (d,d,0) and -q @ (-d,-d,0)
how do i derive a torque?
I know the definition of the electric dipole moment is given by \mu = -e x, where e is the charge of electron and x is the displacement. I am thinking a mechanics counterpart of the dipole moment. We note that in mechanics, the moment is defined as the force cross the position vector. Consider...
Homework Statement
A certain electric dipole is placed in a uniform electric field E of magnitude 20 N/C. Figure 22-59 gives the potential energy U of the dipole versus the angle θ between E and the dipole moment P. What is the magnitude of P?
Homework Equations
U=p(dot)E
The...
Homework Statement
A dipole of moment 0.50 e · nm is placed in a uniform electric field with a magnitude of 8.0 104 N/C. What is the magnitude of the torque on the dipole for each of the following situations?
(a) the dipole is aligned with the electric field
0. N · m (this is correct)...
Homework Statement
Calculate the magnetic vector potential A at a point p located at a distance r from the axis of an oscillating dipole of length s.
It is assumed that r\gg s and that the current is the same throughout s.
Homework Equations
r=\sqrt{(x^2+(z-z')^2)}, where x,z is the...
Find the fi rst integrals of motion for a particle of mass m and charge q in a magnetic field given by the vector potential (scalar potential \Phi= 0)
(i) of a constant magnetic dipole m_{d}
A=\frac{\mu_{0}}{4 pi}\frac{m_{d} \times r}{r^{3}}
Hint: Cylindrical coordinates are useful...
Homework Statement
Given an electrical dipole of electrical dipole momentum \vec P = p\hat k, centered in 0\hat i + 0\hat j + 0\hat k, find the potential in all the space, where V(\infty ) = 0. If the dipole is now surrounded by a hollow spherical conductor (initially discharged), find the...
Is the field of an electric dipole conservative?
Initially I thought it would be, for no particular reason but that's just what my high school intuition thought. (haha I thought everything would be conservative apart from friction)
But I was reading up on some vector calculus and...
Hi All,
I'm currently wrestling with trying to understand the theory behind radiation from a dipole antenna. Little by little I'm putting the pieces together but I need verification regarding a conclusion that I have drawn although I have not read it.
An antenna has a near field and a far...
Dipole Moment!
Ok I'm very tired because I've spent the past 50 minutes trying to figure out a problem that should take only 5. Someone please just take 2 minutes of your time to save me 20 more minutes. THis is a simple problem yet I cannot do it on my own, without my textbook and with what...
Homework Statement
A point charge q is situated a large distance r from a neutral atom of polarizability \alpha. Find the force of attraction between them.
Homework Equations
\vec{E}_{mono}(r)=\frac{q}{4\pi\epsilon_0r^2}\hat{r}...
Hi,
1st year chem guy here...I'm missing this idea. Is it all based upon Electronegativity?
I can see why HBr or HCl and other 2 atom compounds would be polar. 2 atoms with different charges or even sizes creating an un-even pull.
I'm guessing H2O is polar as the 4 remaining electrons on...
Homework Statement
Show that the electric field of a "pure" dipole can be written in the coordinate-free form
E_{dip}(r)=\frac{1}{4\pi\epsilon_0}\frac{1}{r^3}[3(\vec p\cdot \hat r)\hat r-\vec p].
Homework Equations
Starting from
E_{dip}(r)=\frac{p}{4\pi\epsilon_0r^3}(2\cos \hat r+\sin\theta...
Homework Statement
Assume that an electron of mass m and charge magnitude e moves in a circular orbit of radius r about a nucleus. A uniform magnetic field B is then established perpendicular to the plane of the orbit. Assuming also that the radius of the orbit does not change and that the...
Homework Statement
We know the magnitude of the electric field at a location on the x-axis and at a location on the y axis, if we are far from the dipole.
(a) Find \DeltaV= V_p - V_a along a line perpendicular to the axis of a dipole. Do it two ways: from superposition of V due to the two...
I just have a quick question about finding the average force of a dipole.
I am given the expression (after I derived it anyway):
\textbf{F} = -3 \left( \frac{e-1}{e+2} \right) \frac{R^{3}}{d^{7}} \left[4( p \bullet \hat d)^{2} \hat d + p^{2} \hat d - (p \bullet \hat d) \hat d \right]...
Hi
I want to calculate the electric dipole moment of point charges along the z-axis with distances a and with the charge distribution
\varrho (\vec{x}) = q \delta (\vec{x}) - 2q \delta (\vec{x} - \vec{a}) + q \delta (\vec{x} - 2 \vec{a})
and of course \vec{a} = a \vec{e}_{z}
I...
Homework Statement
Can anyone explain why the direction of the dipole moment of an electric dipole is always taken as "from -q to +q" but not "from +q to -q"? In fact when we draw the electric lines of force we are only drawing in such a way that they start from +q and terminate at -q.Then...
Homework Statement
Consider the charge configuration described where two equal but opposite charges of magnitude Q. What is the magnitude of the electric field and the electric potential from the dipole as a function of the distance x from the center of the dipole perpendicular to the dipole...
Homework Statement
I'm trying to find the dipole moment of
The surface charge distribution is:
\sigma = \sigma_{0} sin 2 \theta
Homework Equations
The Attempt at a Solution
p_z=\int_{0}^{\pi}{\sigma* z* dA } = \int_{0}^{\pi}{(\sigma_0 \sin{2...
Homework Statement
Two electrical dipoles with dipole moments \vec{p}_0=p_0\hat{y} and \vec{p}_1=p_1\hat{y} are located in the xy-plane. \vec{p}_0 i located at the origin and \vec{p}_1 is initially in (x,y)=(a,0). What work is required to move \vec{p}_1 (with unhanged directon) to the point...
Calculate the dipole moment of a spherical shell of radius 'a' whose surface charge density is σ=σ0(1+cos(θ)). The origin is at the center of the sphere.
What I know:
1) p=∫r'*ρ*dV'
I'm having trouble understanding how to transform this equation so that I can calculate the dipole moment...
I understand a little about dipole moment. Its like a compass which aligns itself when an external field is applied.
But a little fuzzy when it comes to dipole moment of water. why is it 105 degrees. How does this come into play when they are impinged with microwaves or time varying E field.
Homework Statement
This is a mastering physics question but it does not count for my assessment mark, i am using an alternative approach to the one given in the hints. And off course i got the question wrong but i don't understand why..
"[URL...
Homework Statement
Consider the electric dipole shown in Figure P23.22. Show that the electric field at a distant point on the +x axis is Ex ≈ 4ke qa/x3.
I tried to get a picture but that didn't work out but it basically shows a positive and a negative charge on the x-axis with a distance...
I was hoping people might be able to provide some insight into the following fairly basic scenario (not homework/school related). Imagine a positive point charge on the x-axis. Also on the x-axis, to the right, is an electric dipole, with finite spacing, pointed along the x axis, with the...
hi I am student of graduate and want to clear the picture of MAGNETIC MOMENT of electron in my mind.can someone tell me that if an electron is moving in its orbit constituting its intrinsic spin(1/2) ho can it forms dipole moment(to poles) when place in magnetic field?and what is the difference...
Homework Statement
The graph shows the potential energy of an electric dipole which is in a constant electric field; only the electric force is acting on the dipole. Consider a dipole that oscillates between plus and minus 65 degrees.
a) What is the dipole's mechanical energy?
b) What...
Homework Statement
The figure shows an electric dipole. What is the magnitude of the dipole's electric field at point P, located at distance r >> d?
Homework Equations
The Attempt at a Solution
I suppose I could define the angle with which I could write Ey = Esin\theta, but...
Hy, i am back with my annoying questions about this and that. Could everyone tell me why the frigging dipole have an electric field that drops with 1/r^3? i mean, if i am far away , i should feel no electric field, you know, q2 = -q1 , so they cancel, but i feel (q1 q2 k)/r^3.What the HECK?