#Lights out device before electricity series

The live or hot wire (hereafter referred to as вЂњlive/hotвЂќ) supplies voltage and current to operate the appliance. The third earth/ground is to the case of the appliance, through the green earth/ground wire, forcing the case, too, to be at zero volts. The earth/ground connection closest to the power source could be at the generating plant, while the other is at the userвЂ™s location. Furthermore, the two earth/ground connections supply an alternative path through the earth, a good conductor, to complete the circuit. The neutral wire is the return path for the current to follow to complete the circuit. This wire is therefore safe to touch even if its insulation, usually white, is missing. The two earth/ground connections on the neutral wire force it to be at zero volts relative to the earth, giving the wire its name. Recall that an earth/ground connection is a low-resistance path directly to the earth. There are three connections to earth or ground (hereafter referred to as вЂњearth/groundвЂќ) shown in Figure 2.

Note that wire insulation colors vary with region and it is essential to check locally to determine which color codes are in use (and even if they were followed in the particular installation).

#Lights out device before electricity series

A circuit breaker or fuse protects against thermal overload and is in series on the active (live/hot) wire. Also grounded to zero volts is the case of the appliance. The three-wire system connects the neutral wire to the earth at the voltage source and user location, forcing it to be at zero volts and supplying an alternative return path for the current through the earth. The caseвЂ™s safety feature is that it prevents a person from touching exposed wires and coming into electrical contact with the circuit, helping prevent shocks.ДЇigure 2. Second, there is a protective case around the appliance, such as a toaster or refrigerator. First is the familiar circuit breaker (or fuse) to prevent thermal overload. Modern household and industrial wiring requires the three-wire system, shown schematically in Figure 2, which has several safety features. This is not how power is distributed in practice. Figure 1В shows the schematic for a simple AC circuit with no safety features. Here we will concentrate on systems and devices that prevent electrical hazards. Both hazards have already been discussed. A shock hazard occurs when electric current passes through a person. A thermal hazard occurs when there is electrical overheating.

Explain how various modern safety features in electric circuits work, with an emphasis on how induction is employed.Д®lectricity has two hazards.

By the end of this section, you will be able to: