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Molecular dipole moment definition12/27/2023 ![]() A theoretical magnetic point dipole has a magnetic field of exactly the same form as the electric field of an electric point dipole. The field of a point dipole has a particularly simple form, and the order-1 term in the multipole expansion is precisely the point dipole field.Īlthough there are no known magnetic monopoles in nature, there are magnetic dipoles in the form of the quantum-mechanical spin associated with particles such as electrons (although the accurate description of such effects falls outside of classical electromagnetism). A point (electric) dipole is the limit obtained by letting the separation tend to 0 while keeping the dipole moment fixed. Its field at large distances (i.e., distances large in comparison to the separation of the poles) depends almost entirely on the dipole moment as defined above. 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.įield lines of a point dipole of any type, electric, magnetic, acoustic, etc.Ī physical dipole consists of two equal and opposite point charges: in the literal sense, two poles. However, that means that Earth's geomagnetic north pole is the south pole (south-seeking pole) of its dipole moment and vice versa. In a magnetic compass, the north pole of a bar magnet points north. The dipole moment of the bar magnet points from its magnetic south to its magnetic north pole. 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 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". Strong colors indicate highest and lowest potential (where the opposing charges of the dipole are located).Ī permanent magnet, such as a bar magnet, owes its magnetism to the intrinsic magnetic dipole moment of the electron. ![]() The electron may also have an electric dipole moment though such has yet to be observed (see electron electric dipole moment).Ĭontour plot of the electrostatic potential of a horizontally oriented electrical dipole of infinitesimal size. However, an electron's magnetic dipole moment is not due to a current loop, but to an intrinsic property of the electron. 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. (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.)įor 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. 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. ĭipoles, whether electric or magnetic, can be characterized by their dipole moment, a vector quantity. A bar magnet is an example of a magnet with a permanent magnetic dipole moment. A simple example is a single loop of wire with constant current through it. A magnetic dipole is the closed circulation of an electric current system.(A permanent electric dipole is called an electret.) A simple example of this system is a pair of charges of equal magnitude but opposite sign separated by some typically small distance. ![]() ![]() An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system.In physics, a dipole (from Greek δίς (dis) 'twice', and πόλος (polos) 'axis' ) is an electromagnetic phenomenon which occurs in two ways: By comparison, Earth has a south magnetic pole near its north geographic pole and a north magnetic pole near its south pole. The magnetic field of a sphere with a north magnetic pole at the top and a south magnetic pole at the bottom. ![]()
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