Questions 23-25 Flashcards
- Explain the purpose of a switch.
A switch is an electrical device used to stop, start, or redirect the flow of current in an electrical circuit.
- Define color coding as it relates to switch terminal screws.
The common screw terminal is typically black or darker than the other screws. The terminal is typically bronze or silver. Green always indicates a ground terminal screw.
- Explain the purpose of a UL label.
A UL label is a stamped or printed icon that indicates a device or material has been approved for consumer use by Underwriters Laboratories Inc. Underwriters Laboratories UL was created by the national Board of Firte Underwriters to test electrical materials and devices.
- Why are conductor symbols on switches important?
A conductor symbol is an electrical symbol that represents copper and aluminum respectively. Certain electrical devices are made to work with copper only and some devices with aluminum or copper.
- Identify the typical maximum current and voltage ratings of switches for residential use.
The maximum current rating of a switch for residential use is 15A or 20A. The maximum voltage rating is typically 120V.
- Define T rating.
Switches used to control loads with a tungsten filament (such as standard incandescent lamps) must be marked with a T. A T rating is special switch information that indicates a switch is capable of handling the severe overloading created by a tungsten load as the switch is closed. Tungsten has a very low resistance when cold and increases in resistance as heated.
- Define strip gauge.
Strip gauges are found on the rear portion of a back-wired switch. A strip gauge is a short groove that indicates the amount of insulation that must be removed from a wire so the wire can be properly inserted into a switch. When a wire has not had enough insulation removed, a proper connection is not made. When too much insulation is removed, bare wire is left exposed allowing a short to possibly occur.
- What types of switches are commonly used in residences?
Common switches used in residences s are single-pole, three-way, four-way, and double-pole switches.
- What is signified in “Three-way” in the term three-way switch?
Three-way switches are used in pairs to control a light or load from two locations. The term “three-way” is the given name to the switch and in no way describes the operation of the switch. The terminals of a three-way switch are identified as common, traveler A, and traveler B.
- How is a four-way switch used?
A four-way switch is used in combination with two three-way switches to allow control of a load from three locations. One or more four-way switches are used with two three-way switches to provide control of a load from three or more locations.
- Describe the design of a double-pole switch.
Double-pole switches are designed to connect or disconnect (open or close) at the same time. Double-pole switches are common for 230V circuits where both conductors are hot conductors. Double-pole switches open or close the dual path to the 230 V load, turning the load ON or OFF. Double-pole switches look similar to four-way switches, however double-pole switches are distinctly marked with an ON and OFF position.
- Define receptacle.
Receptacles are often called convenience outlets. A receptacle is a contact device installed for the connection of plugs and flexible cords to supply current to portable electrical equipment.
- How are the shape and position of the connection slots used to indicate the type of receptacle that can be plugged into a receptacle?
A 125 V receptacle has connection slots that are vertical and typically different lengths. A 250 V receptacle has connection slots that are horizontal and the same size.
- What is a polarized receptacle?
A 125 V receptacle with different size connection slots is a polarized receptacle. A polarized receptacle is a receptacle in which the size of the connection slots determines the plug connection. The short connection slot is the hot connection and the long connection slot is the common (neutral) connection.
- What is determined by the ratings on a receptacle?
Ratings determine the number of contacts and the configuration in which the slots are positioned in the receptacle.
- Explain how to wire a standard 120 V duplex receptacle.
When wiring a 120 V duplex receptacle, the black or red (hot) wire is connected to the brass-colored screw, the white wire is connected to the steel colored common screw, and the green or bare wire is connected to the green screw.
- How is a split-wired receptacle different from a standard receptacle?
A split-wired receptacle is a standard receptacle that has had the tab between the two brass-colored (hot) terminal screws removed. The tab between the two steel-colored (neutral) terminals has not been removed. Split wire receptacles are used to provide a standard and switched circuit or two separate circuits at the same duplex outlet.
- What is the purpose of an isolated-ground receptacle?
An isolated ground receptacle is a special receptacle that minimizes electrical noise by providing a separate grounding path for each connected device. A separate ground conductor is run with the circuit conductors in an isolated grounding system.
- How are isolated ground receptacles identified?
Isolated ground receptacles are identified by an orange color.
- What is a ground fault circuit interrupter (GFCI)?
A ground fault circuit interrupter (GFCI) is a fast-acting receptacle that detects low levels of leakage current to ground and opens the circuit in response to the leakage (ground fault).
- Name some of the elements that may be included in a trade-specific language.
This language may include symbols, drawings, diagrams, schematics, words, phrases, and abbreviations.
- List the components of an electrical print.
Electrical prints include pictorial drawings, electrical layouts, schematic diagrams, and line diagrams.
- List the basic parts of any industrial or residential electrical circuit.
The five parts include a component (load) that converts electrical energy into some other usable form of energy such as light, heat, or motion; a source of electricity; conductors to connect the individual devices and components; a method of controlling the flow of electricity (switch); and protection devices (fuses or circuit breakers) to ensure that the circuit operates safely within electrical limits.
- What can be done to manually controlled circuit to make it automatic?
Any manually controlled circuit can be converted to automatic operation. A great example is the use of a photo cell controller controlling lights. Photocell controllers automatically detect the absence of light and respond by sending commands to loads (lights). A photo cell controller responds to the absence of light by turning lights inside or outside a dwelling on.
- Why are electrical plans necessary?
Electrical plans are important, not only do they determine the number of openings in walls and ceilings. They estimate the amount of wire and conduit that is required for the job. Necessary for supplier for material, permits, owner so he can see what he is getting. For supplier so he can see what he is buying.
- How does a component plan differ from a wiring plan?
A wiring plan is a drawing that indicates the placement of all electrical devices and components and the wiring required to connect all the equipment into circuits. A component plan I a group of schedules that state the required locations for receptacles, lights, and switches according to the NEC and local codes.
