Harper's Electricity Book for BoysAdams, Joseph H. (Joseph Henry)
Science
Harper's Electricity Book for Boys
Adams, Joseph H. (Joseph Henry)
Electricity -- Juvenile literature
It is essential in electrical work to have joints, splices, unions, and
contacts made perfectly tight, so that the current will flow through
them uninterruptedly. A poor contact or weak joint may throw a whole
system out of order. For this reason all joints should be soldered
wherever practicable. In line work, however, this is impossible, except
where trolley-wires are joined, and these are brazed in the open air by
an apparatus especially designed for the purpose. In telegraph and
telephone lines perfect contact is absolutely necessary, and where
attachments are made to insulators the main-line should never be turned
around the insulator. The wire is brought up against the insulator, and
with a [U] wire the main-line is tightly bound to it, as shown at Fig.
11. If it is necessary to bind the main-line more securely to the
insulator, one or two turns may be taken around the insulator with the
[U] or anchoring wire; then with a pair of plyers a tight wrap is made.
When joining two ends of wire together, never make loops as shown in
Fig. 12 A. This construction gives poor contact, for the wire loops
will wear and finally break apart. Moreover, the rust that forms between
the loops will often cause an open circuit and one difficult to locate.
Care must be taken to make all splices secure and with perfect contact
of wires, and the only manner in which this can be done is to pass the
ends of wires together for three or four inches, as shown in Fig. 12 B.
[Illustration: FIG. 9]
[Illustration: FIG. 10]
[Illustration: FIG. 11]
[Illustration: FIG. 12]
[Illustration: FIG. 13]
Grasp one wire with a pair of plyers, and with the fingers start the
coil or twist, then with another pair of plyers finish the wrapping
evenly and snugly. Treat the other end in a similar manner, and as a
result you will have the splice pictured in Fig. 12 B, the many wraps
insuring perfect contact. This same method is to be employed for inside
wires, and after the wrap is made heat the joint and touch it with
soldering solution. The solder will run in between the coils and
permanently unite the joint. The bare wires should then be covered with
adhesive tape.
Avoid sharp turns and angles in lines, and where it is not possible to
arrange them otherwise it would be well to put in a curved loop, as
shown at Fig. 13. A represents a pole, B B the line, and C the
quarter-circular loop let in to avoid the sharp turn about the
insulator. The current will pass around the angle as well as through the
loop, but a galvanometer test would show that the greater current passed
through the loop and avoided the sharp turn.
“Grounds”
[Illustration: FIG. 14]
[Illustration: FIG. 15]
[Illustration: FIG. 16]
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