Velocity of Signaling.
The speed of transmission of electric signals is affected by the nature
of the line, as regards its static capacity, and by the delicacy of the
receiving instruments, which may need a more or less strong current to
be affected. Thus of an original current one per cent. may suffice to
operate a sensitive instrument. This might give almost the velocity of
light, while if the instrument would only respond to the full current
nearly two minutes (see Variable State) might be required for the
production of a signal.
Velocity Ratio.
A term applied to the ratios existing between the electrostatic and
electro-magnetic units. If we take as numerators the dimensions of the
different qualities in the electrostatic system, and their dimensions in
the electro-magnetic system as denominators, the fractions thus obtained
reduce to expressions containing only velocity or V in some form. Thus
if we divide the dimensions of the electrostatic quantity by the
dimensions of electro-magnetic quantity the quotient is simply V or
velocity. A like division for potential, electrostatic and
electro-magnetic gives (1/V), and so on.
The value of the velocity ratio is very nearly 3E10 (sometimes given as
2.98E10) centimeters per second. This is almost exactly that of light
(2.9992E10 centimeters per second.) This is one of the proofs of Clerk
Maxwell's magnetic theory of light. (See Maxwell's Theory of Light.)
[Transcriber's note: The SI metre was defined in 1983 such that the
speed of light in a vacuum is exactly 299,792,458 metres per second or
about 186,282.397 miles per second.]
Ventilation of Armature.
In a dynamo or motor ventilation of the armature is often provided for
by apertures through it in order to prevent heating. This heating is
caused by Foucault currents. By proper disposition of the interior of
the armature with properly disposed vanes and orifices an action like
that of a fan blower can be produced, which by creating a current of air
cools the machine very efficiently.
Verticity, Poles of.
Points upon the earth's surface where the horizontal component of
magnetic force disappears, leaving only the vertical component active.
The term is derived from the verticity of the dipping needle when over
either of them.