Fig. 57. AUTOMATIC ELECTRIC BELL.
Bell, Electric.
A bell rung by electricity. Generally it is worked by a current exciting
an electro-magnet, attracting or releasing an armature which is attached
to the vibrating or pivoted tongue of the bell. It may be worked by a
distant switch or press-button, q. v., ringing once for each movement of
the distant switch, etc., or it may be of the vibrating bell type as
shown in the cut. When the current is turned on in this case it attracts
the armature. As this moves towards the poles of the magnet it breaks
the circuit by drawing the contact spring, q. v., away from the contact
point, q. v. This opens the circuit, to whose continuity the contact of
these two parts is essential. The hammer, however, by its momentum
strikes the bell and at once springs back. This again makes the contact
and the hammer is reattracted. This action continues as long as the
circuit is closed at any distant point to which it may be carried. The
ordinary vibrating bell is a typical automatic circuit breaker, q. v.,
this type keeping up the ringing as long as the circuit is closed. Other
bells have no electric contact and simply ring once every time the
circuit is closed. Others worked by an alternating current ring once for
each change of direction of current.
80 STANDARD ELECTRICAL DICTIONARY.
Bell, Electro-mechanical.
A bell which has its striking train operated by a spring or descending
weight, and which train is thrown into action by the release of a detent
or equivalent action by the closing of an electric circuit. It rings for
any given time after being started.
Bell, Indicating.
A bell which by drop-shutter or other indicator connected in circuit
with it, indicates its number or other designation of its call.
Bell, Magneto.
An electric bell operated by the alternating current from a magneto
generator. It has a polarized armature and no circuit breaker. The
armature is attracted first in one direction and then in the other, as
the current alternates and reverses the polarity of the electro-magnet.
Bell, Relay.
A bell operated by a relay circuit.
Bias.
In polarized relay the adjustment of the tongue to lie normally against
one or the other contact. (See Relay, Polarized.)
81 STANDARD ELECTRICAL DICTIONARY.
Fig. 58. RESISTANCE COILS SHOWING BIFILAR WINDING.
Bifilar Winding.
The method followed in winding resistance coils to prevent them from
creating fields of force. The wire is doubled, and the doubled wire
starting with the bend or bight is wound into a coil. The current going
in opposite senses in the two lays of the winding produces no field of
force.
Binary Compound.
A chemical compound whose molecule contains only two elements, such as
water (H2 0), lead oxide (Pb 0), and many others.
Binding.
In a dynamo or motor armature the wire wound around the coils to secure
them in place and prevent their disturbance by centrifugal action.
Fig. 59. DOUBLE BINDING POST.
Fig. 60. BINDING POST, ENGLISH PATTERN.
FIG. 61. WOOD SCREW BINDING POST.
Binding Posts or Screws.
Arrangements for receiving the loose end of a wire of an electric
circuit, and securing such end by a screw. Several constructions are
used, as shown here. Sometimes the wire is passed through a hole, and a
screw tapped in at right angles to the hole is screwed down upon the
wire. Sometimes the wire is clamped between two shoulders, one on the
screw, the other on the post. The screw is often a flat-headed thumb
screw or has a milled edge. Sometimes the screw has a slot and is turned
by a screw-driver.
Several openings are often provided in the same post for different
wires.
Binnacle.
The case containing a mariner's compass on shipboard. It is enclosed
completely; it has a glass side or window through which the compass can
be seen, and is provided with one or two lamps arranged to light the
card, while showing as little light as possible outside.
82 STANDARD ELECTRICAL DICTIONARY.
Bioscopy, Electric.
The diagnosis of life and death by the action of the animal system when
subjected to an electric current or electrification.
Bismuth.
A metal, one of the elements, atomic weight, 210 ; equivalent, 70;
valency, 3; specific gravity, 9.9. It is a conductor of electricity.
Relative Resistance, compressed, (silver = 1) 87.23
Specific Resistance, 131.2 microhms
Resistance of a wire
(a) 1 foot long, weighing 1 grain, 18.44 ohms
(b) 1 foot long, 1/1000 inch thick, 789.3 "
(c) 1 meter long, weighing 1 gram, 12.88 "
(d) 1 meter long, 1 millimeter thick, 1.670 "
Resistance of a 1-inch cube 51.65 microhms
Electro chemical equivalent, .7350 (Hydrogen = .0105)
(See Thermo-electric Series.)
