What is Electric dipole: Definition and 166 Discussions
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".
Electric Dipole and Electric Potential.. and binomial approximation!
Homework Statement
An electric dipole at the origin consists of two charges +q and -q spaced distance s apart along the y-axis.
a.)Find an expression for the potential V(x,y) at an arbitrary point in the xy-plane...
I am participating in a reading course on nonlinear optics, which is a little difficult since I haven't had any formal education in quantum mechanics other than the standard introductory solving of Schroedinger's eqn. in 1D. Happily this course takes the semiclassical approach, in which the...
Homework Statement
find components of the electric field of a pure electric dipole (r>>a)Homework Equations
potential = \varphi(r)=2aqP1(cos\Theta)/4\pi\epsilonor2The Attempt at a Solution
do i just have to find the negative gradient of the potential here? i think that's the right thing to do...
Homework Statement
Find the frequency of oscillation of an electric dipole, of dipole moment p and rotational inertia I, for small amplitudes of oscillation about its equilibrium position in a uniform electric field of magnitude E.
Answer: [(pE/I)^0.5]/(2*pi)
Homework Equations
I...
Homework Statement
An electric dipole in a uniform horizontal electric field is displaced slightly from its equilibrium position, where theta is small. The separation of the charges is 2a, and each of the two particles has mass m. Assuming the dipole is released from this position, show that...
I understand that potential energy of an electric dipole is U(θ)=-pEcosθ where p is the dipole moment, E is the electric field and θ is the angle between vector p vector E.
However i have some doubts about its derivation.
in my readings, the work done is derived as such:
dw=t*d(theta) =...
Homework Statement
Using the general expression for the electric field of a dipole, estabilish a simplified expression for the electric field at a point along the x-axis produced by a dipole (p1) at the origin in the z direction.
Use this to find the energy of a second dipole p2 placed at a...
Hi,can anyone tell me how to calculute magnitude and direction of the electric dipole moment of a system? If the system is a bit complicated? What kind of formula I suppose to use? \vec{p}=q\vec{d}?
Homework Statement
Three metal balls with unequal radii R1 < R2 < R3 are placed at the vertices of an equilateral triangle, whose sides have length a. The balls are connected by thin metal wires. A positively charged rod is brought into contact with one of the balls and transfers an amount of...
Suppose there is an electic dipole that starts to oscillate with frequency ω at t=0, then how long does it take the electric dipole to emit a photon?
We know that the radiant power of such electric dipole calculated from quantum physics is P\left( \omega \right) = \frac{{{\omega ^4}}}{{3\pi...
Electric Dipole Electric Field.. URGENT
Homework Statement
For the electric dipole shown in the figure, express the magnitude of the resulting electric field as a function of the perpendicular distance x from the center of the dipole axis in terms of the electric dipole moment, p.
Homework...
Homework Statement
Show that
E = \frac {q}{4\pi\varepsilon(z-\frac{1}{2}d)^2} - \frac{q}{4\pi\varepsilon(z+\frac{1}{2}d)^2}
is
E = \frac {q}{4\pi\varepsilon z^2} [(1-\frac{d}{2z})^{-2} - (1+\frac{d}{2z})^{-2}]
Homework Equations
The Attempt at a Solution
After...
I have an electrodynamics question stemming from a recent episode of the game show "1 vs 100" in which I disagreed with the show's answer.
The question is: "You touch your grandma's elbow and feel a spark. What do you have an excess build-up of, besides shame?"
Answer choices were...
When using k.p theory to calculate the magnitude of the electric dipole moment in semiconductors for band-to-band transitions, the value of the dipole moment is basically fitted to the effective mass of the electron in the conduction band. However, the values turn out to be larger than the...
Homework Statement
An electric dipole (something that has charge +q on one end and charge -q on the other end separated by a distance 2a) is in a uniform horizontal electric field of magnitude E. Initially the electric dipole is aligned horizontally until it is displaced slightly by an angle...
One excersise of my current homework for experimental physics (Ba, 4th term) is giving me troubles, because I have no idea where to start.
Excersise:
Stark effect: Calculate the electric dipole moment for the interference of 2s and 2p (m=0) states (hydrogen).
The wave functions are given...
Dear all
I have done some studies trying to understand the relation between the QCD theta angle and neutron electric dipole moment.
General, the QCD vacuum produces the term
L_{\theta} = \theta g_s^2\: G_a^{\mu\nu} \, G^a_{\mu\nu}
this I can derive! I have studied Srednicki ch 93, Ramond...
potential due to electric dipole is
V = p.r / 4(pi)(epsilon)r3
show the tangential component of the electrical field is
= psin(theta) / 4(pi)(epsilon)r3what I've tried:
i assumed there are 2 charges separated by distance r
potential difference U = qV = -qE.r
so can i say...
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...
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...
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
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 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
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
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
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...
microwave can be used to engineering potentials for alkali atoms
i find that in the literature, people only take the magnetic dipole transition into account
why the electric dipole transition is neglected?
is it forbidden?
Homework Statement
Two point charges likes those in the figure below are called an electric dipole. Show that the electric field at a distant point along the x-axis is given by E_{x}=\frac{4k_{e}qa}{x^3}
Figure: http://img300.imageshack.us/my.php?image=58ag9.png
Homework Equations...
As per my understanding, the position of most stable equilibrium of a dipole placed in a uniform electric field is when it is aligned with the field, i.e. when E and p (dipole moment) are in the same direction. Also the position of most unstable equilibrium is at the position where the dipole...
Help me to sort out this problem:: Prove that, "integration over[J(r)dr]=del(p)/del(t)" ... where p is the electric dipole moment ... please as soon as possible, reply me ...
Homework Statement
Hey everyone, I need to derive what the E and B fields look like for the electric dipole in the near field region close to the source i.e. lambda>>r.
Homework Equations
The Attempt at a Solution
I managed to derive it for the situation far from the source but...
Homework Statement
The eletric dipole of the atom D = qR is a vector op, ie transforms according to j = 1 rep of SU(2). Use wigner eckart theorem show
<1, 0, 0|D|1, 0, 0> = 0
(<n',l',m'|D|n, l, m> = 0
Homework Equations...
1. In an electric dipole moment, assume that both charges are positive and find the electric field "E" at point "P", assuming X>>d, where "d" is the distance between the two charges and "X" is the distance of point "P" from the center of the dipole.
I have thought a lot about it but I am very...
Homework Statement
I got this problem from my physics textbook, and I'm not sure how to solve it.
A point charge R is distance p from the center of a diple consisting of charges + and - q separated by distance s.
The charge R is located in the plane that bisects the dipole.
What is...
An electric dipole consists of a pair of point charges each of magnitude 4nC separated by a distance of 6cm. What is the electric field strength at the point midway between the charges?
Not sure what equations to use?
Any ideas?
Homework Statement
A dipole, consisting of a charge -q at position vector r and a charge +q at position vector r+s, is sitting in an external electric field E(ext).
(a) Write down the total force on the dipole F(dipole) due to the external field
(b) Show that when s is small...
Homework Statement
Show that a line of charge density \lambda exerts an attractive force on an electric dipole with magnitude F = \frac{2\lambda p}{4\pi\epsilon_{0}r^{2}}. Assume that r is much larger than the charge separation in the dipole.
Homework Equations
I need to show that the...
Homework Statement
I we know the eigenstates of the system be |\psi_1\rangle and |\psi_2\rangle. Current state of the system is
|\Psi\rangle = c_1 |\psi_1\rangle + c_2 |\psi_2\rangle
Try to find the expectation value of electric dipole moment \mu (assume it is real) and write it in...
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...
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...
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...
[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
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...
Homework Statement
An electric dipole of moment p is placed at a distance r from a point charge +q. The angle between p and r is phi. Show that the energy of interaction between the dipole and the charge is -pqcos(phi)/4\pi\epsilon0r^2
Derive equations for
a)a radial force on the dipole
b)a...
Homework Statement
For \Deltal = 0 the transition rate can be obtained by evaluating the electric dipole matrix elements
given by
\vec{I} = \int \Psi^{*}_{1,0,0} (e \vec{r}) \Psi_{2,0,0} d\tau
Homework Equations
The Attempt at a Solution
I've got the two wave functions...