题干

居民楼的楼道里,夜间楼道灯一直亮着会造成浪费.科研人员用“光敏”材料制成“光控开关”,它能在天黑时自动闭合,天亮时自动断开;利用“声敏”材料制成“声控开关”.它能在有人走动发出声音时闭合,无人走动时自动断开.请将如图的“光控开关”、“声控开关”、灯泡用笔画线代替导线正确连入电路,设计出只有在夜间且有声音时灯才亮的楼道灯自动控制电路,同时安装一个不受开关控制的三孔插座.

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答案(点此获取答案解析)

解:

由题意知,只有当“光控开关”、“声控开关”都闭合了灯才能亮,故这两个开关与灯串联,且火线要先过开关,再接入灯泡顶部的金属点,零线接入螺旋套;

三孔插座与灯泡并联,其接法为:左零右火上接地,如图所示:

同类题4

任务型阅读

The Farmers' Fresh Market

    This morning,I went to the Farmers Market in Burlington ,Vermont. I didn't know what the Farmers Market is or how to get there.____

    First ,I had to decide how to go there,and I chose both to walk and to take a bus. When I went,I would walk and when I came back,I would take a bus.____

Walking to the market in this city,I was surprised because every house was beautiful,and they were all arranged in good order. In Korea's cities,most houses are not like that,and many apartments are like boxes which often screen off beautiful views like hills and mountains. Also,every road is not straight and narrow.____

    ____It was a very small market,but a very interesting one. I don't know why farmers go there to sell vegetables or why people go there to buy them because there are many more products in large supermarkets.____

    Also ,all the things sold there were very novel. In addition to fresh food,there was homemade food and many other things such as woolen blankets,quilts ,and wooden products.

    I wanted to buy some of them,but I didn't need them,so I just looked at them. It was a very exciting experience.

A. I visited a flower stand at the market.

B. Anyway,I was able to find the Farmers' Market.

C. So, to me, this American town was very impressive.

D. I decided to go early because the market is held in the morning.

E. I knew that it would take a long time to walk,but I wanted to see an American town.

F. I was attracted by the comfortable houses where they lived and the cars that they drove.

G. I think the reason is that the ones sold in the Farmers' Market are fresher and cheaper.