問題詳情

四、長篇閱讀(第 41−50 題)說明：下列二篇文章共有 10 個問題，閱讀後請依文意與題意選出最恰當的選項，並將代號標示在答案卡上。The electricity generated by a power plant and delivered to your home by your local utility iscalled alternating current (AC) because it flows alternatively, first in one direction then in the opposite,completing 60 cycles every second. Batteries produce DC or direct current. From the power plant,current travels over high-voltage transmission lines to substations, where transformers reduce thevoltage for distribution to local lines. Neighborhood transformers lower voltage to 120 and 240 voltsfor home delivery.Most homes built after World War II have three-wire electrical service, in which a neutral wireand two 120-volt hot wires provide 100 to 200 or more amps at both 120 and 240 volts. Older homesmay still have two-wire service, in which one neutral and one hot wire deliver 30 to 60 amps at 120volts only.Electrical service may be routed to a home through overhead wires running from the nearestutility pole to the service entrance head located high on one side of the house. Here the utility’s wiresare spliced to the service entrance wires, which are usually encased in metal or plastic tubing, calledconduit, or combined in a service entrance cable. From the service head, the wires pass through a meter,which records your electricity use, and into the main service panel, where current is split and distributedthrough branch circuits throughout the house. Alternatively, electric service may be routedunderground to a home.
41.aWhat is the use of a “transformer” mentioned in this passage?
(A) To record the electricity use
(B) To change electricity from AC to DC
(C) To lower voltage for local distribution
(D) To do power transfusion

參考答案

答案：C
難度：非常困難0
統計：A(2),B(2),C(0),D(0),E(0)

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