|
| |
Back
Table 1-2.—Standard Solid Copper (American Wire Gauge) | Up
Neets Module 04-Introduction to Electrical Conductors, Wiring Techniques, and Schematic Reading | Next
Figure 1-6.—Stranded conductor |
1-9
Solution: Under the gauge number column, find size AWG 20. Now read across the columns until
you reach the "ohms per 1,000 feet for 25º C (77º F)" column. You will find that the wire
will offer 10.4 ohms of resistance to current flow. Since we are using 2,000 feet of wire,
multiply by 2.
10.4 ohms ´ 2 = 20.8 ohms
An American Standard Wire Gauge (figure 1-4) is used to measure wires ranging in size from
number 0 to number 36. To use this gauge, insert the wire to be measured into the smallest slot that will
just accommodate the bare wire. The gauge number on that slot indicates the wire size. The front part of
the slot has parallel sides, and this is where the wire measurement is taken. It should not be confused with
the larger semicircular opening at the rear of the slot. The rear opening simply permits the free movement
of the wire all the way through the slot.
Figure 1-4.—Wire gauge.
Q9.
Using table 1-2, determine the resistance of 1,500 feet of AWG 20 wire at 25º
C.
Q10.
When using an American Standard Wire Gauge to determine the size of a wire, where should
you place the wire in the gauge to get the correct measurement?
STRANDED WIRES AND CABLES
A wire is a single slender rod or filament of drawn metal. This definition restricts the term to what
would ordinarily be understood as "solid wire." The word "slender" is used because the length of a wire is
usually large when compared to its diameter. If a wire is covered with insulation, it is an insulated wire.
Although the term "wire" properly refers to the metal, it also includes the insulation.
A conductor is a wire suitable for carrying an electric current.
A stranded conductor is a conductor composed of a group of wires or of any combination of groups
of wires. The wires in a stranded conductor are usually twisted together and not insulated from each other.
A cable is either a stranded conductor (single-conductor cable) or a combination of conductors
insulated from one another (multiple-conductor cable). The term "cable" is a general one and usually
applies only to the larger sizes of conductors. A small cable is more often called a stranded wire or cord
(such as that used for an iron or a lamp cord). Cables may be bare or insulated. Insulated cables may be
sheathed (covered) with lead, or protective armor. Figure 1-5 shows different types of wire and cable used
in the Navy.
|
