MAGNITUDE RATIO

The ratio of relative brightness of two celestial bodies differing in magnitude by 1.0. This ratio is 2.512, the 5th root of 100. A body of magnitude 1.0 is 2.512 times as bright as a body of magnitude 2.0, etc.

Related Terms

GEARBOX

A system of gears which alter the ratio between the revolution of the engine and the propeller shaft so the propeller operates in a relatively efficient speed range. By using a gearbox the engine and the propeller shaft will revolve at different speeds.

AMPLIFICATION

1. An increase in signal magnitude from one point to another, or the process causing this increase.
2. Of a transducer, the scalar ratio of the signal output to the signal input

DIRECTIVITY FACTOR

1. The ratio of radiated sound intensity at a remote point on the principal axis of a loudspeaker or other transducer, to the average intensity of the sound transmitted through a sphere passing through the remote point and concentric with the transducer; the frequency must be stated.
2. The ratio of the square of the voltage produced by sound waves arriving parallel to the principal axis of a microphone or other receiving transducer, to the mean square of the voltage that would be produced if sound waves having the same frequency and mean-square pressure were arriving simultaneously from all directions with random phase; the frequency must be stated.

FORM FACTOR

1. The ratio of the effective value of a periodic function, such as an alternating current, to its average absolute value.
2. A factor that takes the shape of a coil into account when computing its inductance. Also known as the shape factor.
3. The theoretical stress concentration factor for a given shape, for a perfectly elastic material.

POISSON RATIO

The ratio of the transverse contracting strain to the elongation strain when a rod is stretched by forces which are applied at its ends and which are parallel to the rod's axis.

PLATE MODULUS

The ratio of the stress component Txx in an isotropic, elastic body obeying a generalized Hooke's law to the corresponding strain component Sxx, when the strain components Syy and Szz are 0; the sum of the Poisson ratio and twice the rigidity modulus.

PLANT FACTOR

The ratio of the average power load of an electric power plant to its rated capacity. Also known as capacity factor.

PHOTOELECTRIC CONSTANT

The ratio of the frequency of radiation causing emission of photoelectrons to the voltage corresponding to the energy absorbed by a photoelectron; equal to Planck's constant divided by the electron charge.

PHASE MARGIN

The difference between 180 and the phase of the loop ratio of a stable system at the gain-crossover frequency.

PERFORMANCE INDEX

The ratio of standard hours to the hours of work actually used; a ratio exceeding 1.00 (or 100) indicates subsoil and rocks in which the contained water is permanently frozen.

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