Technician A says a fuse will automatically reset after the cause of the overload is repaired. Technician B says when an overload occurs, the protection device creates an open. Who is correct?

Only Technician B.

Explanation:

Every electric circuit in a wiring system must be protected against overloads. An overload occurs when equipment is subjected to current above its rated capacity, that is, when the amount of current flowing through the circuit exceeds the rating of the protective devices, and this can cause damages.

For example, if a circuit is rated for 20 amps maximum, then a fuse or circuit breaker of that rating will be in that circuit. Then if the current exceeds 20 amps, the circuit breaker will create an opening, cutting off any more current flow.

the earth’s crust is broken into separate pieces called tectonic plates (fig. 7.14). recall that the crust is the solid, rocky, outer shell of the planet. it is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. both types of crust rest atop solid, upper mantle material. the upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

each tectonic plate is free-floating and can move independently. earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. the term fault is used to describe the boundary between tectonic plates. most of the earthquakes and volcanoes around the pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. other observable results of short-term plate movement include the gradual widening of the great rift lakes in eastern africa and the rising of the himalayan mountain range. the motion of plates can be described in four general patterns:

collision: when two continental plates are shoved together

subduction: when one plate plunges beneath another (fig. 7.15)

spreading: when two plates are pushed apart (fig. 7.15)

transform faulting: when two plates slide past each other (fig. 7.15)