Multipole

In physics, a multipole is any spatial arrangement of ( electrical or other) discrete charges or, in the magnetic case, of dipoles . By multipole expansion , a potential field can be approximated by point charges .

Important special cases are:

• Monopoly (one charge)
• Dipole (two charges)
• Quadrupole (four charges).

In physics, one considers the spherical multipole expansion of fields according to spherical surface functions and the associated multipole moments more generally . Then = 0 corresponds to the monopole, = 1 to the dipole, = 2 to the quadrupole, = 3 to the octupole, etc. ${\displaystyle Y_{lm}}$ ${\displaystyle q_{lm}}$ ${\displaystyle l}$ ${\displaystyle l}$ ${\displaystyle l}$ ${\displaystyle l}$

In pneumatics , for example in valve terminals , the joint control of several valves is referred to as a multipole.