# form factor

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## form factor

[′fȯrm ‚fak·tər]
(electricity)
The ratio of the effective value of a periodic function, such as an alternating current, to its average absolute value.
A factor that takes the shape of a coil into account when computing its inductance. Also known as shape factor.
(mechanics)
The theoretical stress concentration factor for a given shape, for a perfectly elastic material.
(physics)
A function which describes the internal structure of a particle, allowing calculations to be made even though the structure is unknown.
(quantum mechanics)
An expression used in studying the scattering of electrons or radiation from atoms, nuclei, or elementary particles, which gives the deviation from point particle scattering due to the distribution of charge and current in the target.

## Form Factor

a function that characterizes the distribution of the electric charge or magnetic moment within some microsystem, such as an atom or atomic nucleus, or within an elementary particle. The form factor of an atom is determined by the distribution of atomic electrons; the form factor of a nucleus is determined primarily by the distribution of nucleons (protons and neutrons) within the nucleus. In the latter case, virtual mesons also contribute to the form factor; they are the basis for the nucleon exchange that gives rise to nuclear forces. The existence of a form factor has also been established for strongly interacting elementary particles—hadrons, such as nucleons and pions. Experiments on the elastic scattering of high-energy electrons and muons by hadrons lead to the conclusion that the size of the region over which the electric charges and magnetic moments of the hadrons are distributed is of the order of 10–13 cm. These data directly attest to the complex structure of hadrons. At the same time, experiments indicate that the maximum range at which the charge of an electron or muon is appreciable does not exceed 10–15cm.

The form factor of hadrons that characterizes the dimensions of hadrons in processes involving the weak interaction is postulated by analogy with form factors characterizing the distribution of magnetic moment.

S. S. GERSHTEIN

## form factor

(hardware)
The type of packaging of a processor integrated circuit, e.g. PPGA, FC-PGA.

More generally, a term popular among marketroids in 1998, denoting the shape of something designed.

## form factor

The physical size of a device as measured by outside dimensions. With regard to a disk drive, the form factor is the diameter of the platters, such as 2.5", 3.5" and 5.25", not size in terms of storage capacity. See footprint.
References in periodicals archive ?
In choosing a physical form factor for their FC support, OEMs need first to categorize the types of customers they serve, and the types of servers they produce for those customers.
90 software modem into its Presario 1200T, 1400, 1600 and 1700 notebooks, utilizing the same industry-standard mini-PCI form factor.

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