Variometer.
An apparatus used in determining the relative values of the horizontal
component of the earth's magnetic field in different places.
Varley's Condenser.
A static condenser whose conducting surfaces are platinum electrodes
immersed in dilute sulphuric acid. When the potential difference is
1/50th that of a Daniell's cell, two square inches of platinum have a
capacity equal to that of an air condenser whose plates have an area of
80,000,000 square inches, and separated 1/8th of an inch from each
other. As the E. M. F. increases the capacity also increases.
Varley's Resistances.
Variable resistances formed of discs of carbonized cloth, q. v., piled
up, and pressed together more or less firmly to vary the resistance as
desired.
Varnish.
A glossy transparent coating of the nature of paint, applied as a
protective, or ornamental coating to objects.
Varnish, Electric.
Alcoholic or etherial varnishes are the best for electrical apparatus.
They dry quickly and perfectly, and tend to form surfaces unfavorable to
the hygroscopic collection of water. Sealing wax dissolved in alcohol,
or shellac dissolved in the same solvent are used for electrical
apparatus, although the first is rather a lacquer than a varnish.
Etherial solution of gum-copal is used to agglomerate coils of wire. It
is well to bake varnished objects to harden the coating.
Varnish, Red.
A solution of sealing wax in 90 per cent. alcohol. It is best made thin
and applied in several coats, each coat being allowed to dry perfectly
before the next is applied. It is often seen on Leyden jars. It is a
protector from surface leakage.
Vat.
A vessel for chemical or other solutions. A depositing vat is one in
which a plating solution is worked, for the deposition of electroplate
upon articles immersed in the liquid, and electrolyzed by an electric
current.
Velocity.
The rate of motion of a body. It is usually expressed in distance
traversed per second of time. The absolute unit is one centimeter per
second or kine. The foot per second is very largely used also.
The dimensions of velocity are length (L) divided by time (T) or L/T.
Velocity, Angular.
Velocity in a circle defined by the unit angle, or the angle which
subtends a circular arc equal in length to itself. The radius of the
circle traversed by the moving body does not enter into this definition,
as the real velocity of the object is not stated. If its angular
velocity and the radius of the path it travels are given its actual
velocity can be deduced.