Magnetic Dipole - Dipolar Fields From Finite Sources

Dipolar Fields From Finite Sources

See also: Near and far field

The magnetic scalar potential ψ produced by a finite source, but external to it, can be represented by a multipole expansion. Each term in the expansion is associated with a characteristic moment and a potential having a characteristic rate of decrease with distance r from the source. Monopole moments have a 1/r rate of decrease, dipole moments have a 1/r2 rate, quadrupole moments have a 1/r3 rate, and so on. The higher the order, the faster the potential drops off. Since the lowest-order term observed in magnetic sources is the dipolar term, it dominates at large distances. Therefore, at large distances any magnetic source looks like a dipole with the same magnetic moment.

Read more about this topic:  Magnetic Dipole

Famous quotes containing the words fields, finite and/or sources:

    “The sun was like a great visiting presence that stimulated and took its due from all animal energy. When it flung wide its cloak and stepped down over the edge of the fields at evening, it left behind it a spent and exhausted world.”
    —Willa Cather (1873–1947)

    “Put shortly, these are the two views, then. One, that man is intrinsically good, spoilt by circumstance; and the other that he is intrinsically limited, but disciplined by order and tradition to something fairly decent. To the one party man’s nature is like a well, to the other like a bucket. The view which regards him like a well, a reservoir full of possibilities, I call the romantic; the one which regards him as a very finite and fixed creature, I call the classical.”
    —Thomas Ernest Hulme (1883–1917)

    “Even healthy families need outside sources of moral guidance to keep those tensions from imploding—and this means, among other things, a public philosophy of gender equality and concern for child welfare. When instead the larger culture aggrandizes wife beaters, degrades women or nods approvingly at child slappers, the family gets a little more dangerous for everyone, and so, inevitably, does the larger world.”
    —Barbara Ehrenreich (20th century)