thoughtful Ent_ What ampacity must all branch-circuit conductors used for wiring a ceiling outlet box be de-rated at? Select one: a.
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60°C. Branch-circuit conductors are typically rated at 60°C unless otherwise specified. Show more…
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Che wiring circuit for a typical room is shown schematically. (a) Of the six locations for a circuit breaker indicated by $A, B, C, D, E,$ and $F,$ which one would best protect the wiring against a short circuit in any one of the three appliances? Explain. (b) The potential difference between hot and neutral is $120 \mathrm{V}$. Suppose the heater draws $1500 \mathrm{W}$, the lamp draws $300 \mathrm{W}$, and the microwave draws 1200 W. The circuit breaker is rated at 20.0 A. Can all three devices be operated simultaneously without tripping the breaker? Explain.
The wiring circuit for a typical room is shown schematically. (a) Of the six locations for a circuit breaker indicated by $A, B, C, D, E,$ and $F,$ which one would best protect the household against a short circuit in any one of the three appliances? Explain. (b) The room circuit is supplied with $120 \mathrm{V}$. Suppose the heater draws $1500 \mathrm{W}$ the lamp draws $300 \mathrm{W},$ and the microwave draws $1200 \mathrm{W}$ The circuit breaker is rated at $20.0 \mathrm{A} .$ Can all three devices be operated simultaneously without tripping the breaker? Explain.
According to the U.S. National Electrical Code, copper wire used for interior wiring of houses, hotels, office buildings, and industrial plants is permitted to carry no more than a specified maximum amount of current. The table shows values of the maximum current $I_{\max }$ for several common sizes of wire with varnished cambric insulation. The "wire gauge" is a standard used to describe the diameter of wires. Note that the larger the diameter of the wire, the smaller the wire gauge. $$ \begin{array}{ccc} \text { Wire gauge } & \text { Diameter }(\mathrm{cm}) & I_{\max }(\mathrm{A}) \\ \hline 14 & 0.163 & 18 \\ 12 & 0.205 & 25 \\ 10 & 0.259 & 30 \\ 8 & 0.326 & 40 \\ 6 & 0.412 & 60 \\ 5 & 0.462 & 65 \\ 4 & 0.519 & 85 \end{array} $$ (a) What considerations determine the maximum current-carrying capacity of household wiring? (b) A total of $4200 \mathrm{~W}$ of power is to be supplied through the wires of a house to the household electrical appliances. If the potential difference across the group of appliances is $120 \mathrm{~V},$ determine the gauge of the thinnest permissible wire that can be used. (c) Suppose the wire used in this house is of the gauge found in part (b) and has total length $42.0 \mathrm{~m}$. At what rate is energy dissipated in the wires? (d) The house is built in a community where the consumer cost of electrical energy is $\$ 0.11$ per kilowatt-hour. If the house were built with wire of the next larger diameter than that found in part (b), what would be the savings in electricity costs in one year? Assume that the appliances are kept on for an average of 12 hours a day.
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