True Contact Force.
A species of electro-motive force whose existence is supposed to be
proved by the Peltier effect. The lowering in temperature of a contact
of dissimilar metals is attributed to a force that helps the current on
its way if in the direction of thermo-current proper to the junction and
opposing it if in the reverse. The true contact force is taken to
explain this phenomenon; thermo-electric force cannot, as there is no
heat or cold applied to the junction.
Trumpet, Electric.
An apparatus consisting of a vibrating tongue, kept in motion by
electricity as in the buzzer, q. v., placed in the small end of a
trumpet-shaped tube.
Trunking Switchboard.
A telephone switchboard arranged in sections, which sections are
connected by trunk lines, through which trunk lines the desired
connections
are made.
Trunk Lines.
In telephone distribution systems, the lines connecting different
stations, or different sections of a switch-board and used by anyone
requiring such connections; one trunk line answers for a number of
subscribers.
Tube, Electric.
A tube of glass around which is pasted a series of tinfoil circles,
diamonds, or little squares, or other form of interrupted conductor. The
pieces generally are placed in the line of a spiral. When a static
discharge of electricity takes place along the conductor a row of bright
sparks is produced at the breaks in the conductor. These by reflection
are multiplied apparently, and a beautiful effect of intersecting or
crossing spirals of sparks is presented.
The experiment is in line with the luminous pane and lightning jar, and
is used merely as a demonstration, or lecture experiment.
Synonym--Luminous Tube.
Tubular Braid.
A braid woven of tissue or worsted, and tubular or hollow. Its object is
to provide a covering which can be drawn over joints in covered wires.
In making the joint the ends of the wires are necessarily bared, and a
short piece of tubular braid is used for covering them. It is drawn by
hand over the joint.
Turns.
An expression applied to the convolutions of wire in a solenoid,
electro-magnet, or other apparatus or construction of that kind. A turn
indicates a complete encircling of the core or axis of the object. Thus
a wire wound five times around a bar gives five turns.
While this is its primary meaning the term if compounded may refer to
virtual turns. Thus an ampere-turn means one ampere passing through one
turn. But ten ampere-turns may mean ten amperes passing through ten
turns, five amperes passing through two turns, and so on. This use is
analogous to a dimension of length in a compound word, as foot-pound.
[Transcriber's note: "But ten ampere-turns may mean ten amperes passing
through ONE turn or one ampere through ten turns, and so on."]
There may be a number of kinds of turns qualified by descriptive
adjectives, as series-turns, the turns of wire in a series circuit of a
compound dynamo. In the same way there are shunt-turns. If series
ampere-turns or shunt ampere-turns are meant the word ampere should be
included.