STRB软启动器从受令开始到电机停转约需要() A.20s B.30s C.40s

题型:单项选择题

问题:

STRB软启动器从受令开始到电机停转约需要()

A.20s

B.30s

C.40s

D.50s

考点:维修电工考试维修电工(高级)维修电工(高级)题库
题型:单项选择题

判断下列句子是否符合短文内容。符合的写T,不符合的写F.(T=True,F=False)

Beijing is the capital of China and can be easily reached by train, plane or bus. There are two main train stations in Beijing. One is in the center and can be reached by subway; the other is in the southwest of Beijing and can easily be reached by bus.

The city itself has good transportation. The total length of the subway in the city is about 200 km. It’s convenient. Passengers can buy tickets from vending machines at entrances to the subway.

The roads in the city are excellent . The traffic runs quite well except during rush hours(高峰期) in the morning and evening when people drive to and from work .

Some buses in Beijing have a box near the driver . You can put money into the box when you get on the bus . Payment on these buses is usually one Yuan no matter (无论)how far you go . Other buses have a conductor. His or her job is to collect money from passengers . On these buses , the price is usually based on(依据) how far you travel .

小题1:. You can’t get to Beijing by ship .

小题2:. There’re two main subway stations in Beijing .

小题3:. Passengers can buy tickets at entrances to the subway.

小题4:. There’re no conductors on all the buses .

小题5:. No matter how far you go , you only need to pay one Yuan

题型:单项选择题

在如图甲所示储能电站中,蓄水池A中的水通过管道B推动水轮机带动发电机发电。用电低峰时潜水泵把水从D池抽到A池。图乙是储能发电控制原理图,水流接口与图甲中的管道B的最低点接通。白天光控开关闭合,当水的压强大于ρh2g时弹簧推动开关K使1和2两点接通,在电磁继电器作用下触点3与5接通,电动水闸M打开,水流通过管道B推动发电机工作,夜晚光控开关断开或白天水压不足以推动开关K时,电动水闸M关闭,发电机停止工作。

(1)发电机发电过程中的能量转化是_______________。

(2)请完成乙图的电路连接。

(3)若圆柱形储水池A的半径为R,如图甲所示,0点为整池水的重心,A池的顶部距最低点B的距离为H,OB两点距离为h1,池底与B点的距离为h2,若发电机的效率为80%,A池装满一池水时,该发电设备一次能发多少电能?若一次发电时间为t,则发电机的发电功率为多少?(忽略水管直径和发电机的大小,要求写出推导过程,不要求代入具体数据计算)。

题型:单项选择题

Yuan Long-ping has devoted all his life to the agricultural research, and finally his efforts ________him great achievement and world fame.

A.earned

B.offered

C.presented

D.directed

题型:单项选择题

1895年美国300家大型垄断公司组成“全国制造商协会”。协会设有各种常务委员会研究对内对外政策,并由顾问委员会同政府联系,这表明 [ ]

A.美国国家垄断资本主义产生   

B.国家加强对经济的干预   

C.垄断资本家干涉国家的政治经济生活   

D.美国民主政治不断完善

题型:单项选择题

原发性疱疹性口炎常见于()

A.老年人

B.中年人

C.青年人

D.妇女

E.婴幼儿

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