Rheomotor.
A source of current; a current generator; a producer of potential
difference. (Obsolete.)
Rheophore.
The portion of an active circuit capable of deflecting a magnetic
needle. This properly includes all of the metallic conductor of a
circuit. (Obsolete.)
Rheoscope.
A galvanoscope; an instrument for qualitatively detecting potential
difference, fall or rise. (See Galvanoscope.)
Rheostat.
An adjustable resistance; an apparatus for changing the resistance
without opening the circuit. Its action may depend on the introduction
of variable lengths of mercury column, of some other liquid, or of wire
into a circuit. (See Rheostat, Wheatstone's.)
Rheostat Arm.
The third arm of known resistance in a Wheatstone bridge. (See
Proportionate Arms.)
Rheostatic Machine.
An apparatus for increasing potential difference. It consists of a
number of static condensers. They are charged in multiple arc or in
parallel, and are discharged in series. Secondary batteries may be used
for the charging; thus a static effect is produced from a galvanic
battery.
Rheostat, Wheatstone's.
This apparatus consists of two cylinders, one, A, made of brass, the
other, B, of wood, with a spiral groove. At its end is a copper ring a.
A fine brass wire has one end attached to this ring. Its other end is
fastened at e, and it is wound as shown; n and o are binding screws
connected, one with the cylinder-ring a, the other with the brass
cylinder, A. The current entering at o, traverses the wire on B, as
there the windings are insulated by the grooves, thence it passes to m
and by A, whose metal short circuits all the wire on it, to the
binding-post n. The handle, d, is turned one way or the other to
regulate the length of the wire through which the current must pass. On
each cylinder there is a square head, one of which is shown at c, so
that the handle can be shifted from one to the other as required; to A
if the wire is to be wound on that cylinder, to B if the reverse is
desired.
Fig. 297. WHEATSTONE'S RHEOSTAT.