Chapter 3 Introduction to Basic Electrical Circuit Materials 63
For example, a three-amp fuse is designed to burn
and open the circuit when the current exceeds three amps.
A load that draws three amps or greater will generate suf-
ficient heat in the fuse to melt the fuse link inside the
glass tube. The time required to melt the fuse link is
inversely proportional to the amount of overload. This
means that the higher the overload current, the faster the
melting action occurs. When a fuse melts, it must be
replaced.
A circuit breaker, sometimes called a reset, is
another device used to protect a circuit from overload and
short circuit conditions. See Figure 3-19. The main
advantage of a circuit breaker over the fuse link is that the
circuit breaker need not be replaced after tripping. It can
be reset by moving the handle to the off position and then
returning it to the on position. Some circuit breakers have
Ring terminal
Insulated ring terminal
Flange terminal
Inline splice
Crimping area
Termination block
Fork terminal
Stranded conductor
Wire
cutter
crimping
holes
Insulation
stripping
holes
Insulated
handles
Figure 3-16. Some wire connectors are made to be crimped on the end of stranded conductors. After the connector is
crimped on the wire, the wire can be easily secured under a termination block screw.
Wire nut
connector
Conductors are twisted
together and then
inserted inside the wire
nut solderless connector.
The wire nut is then
twisted onto the
conductors, finishing
the connection.
Two or more conductors are
inserted into the slot. The nut
is turned with a wrench and tightens
the conductors together.
Nut
Split-bolt connector
Figure 3-17. Two types of solderless connectors are the
wire nut connector and the split-bolt connector. The wire
nut is used extensively in residential and commercial
wiring. The split-bolt connector is used mainly on large
diameter conductors.
Figure 3-18. A typical fuse and the schematic symbol that
represents the fuse.