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对地电压指带电体与零电位大地之间的电位差。下图为TT系统(即配电变压器低压中性点(N点)直接接地,用电设备(M)的外壳也直接接地的系统)示意图。已知低压中性点接地电阻RN=1Ω、设备外壳接地电阻RM=3Ω、配电线路相电压U=220V。当用电设备发生金属性漏电(即接触电阻接近于零)时,该设备外壳对地电压为( )V。
A.
55
B.
120
C.
165
D.
185
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【简答题】Chinese writer Mo Yan has won the 2012 Nobel Prize in Literature, announced the Swedish Academy in Stockholm on Thursday.The win makes Mo Yan the first Chinese citizen to win the Nobel in its history....
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【简答题】点在直线上,点的正投影一定在该直线的正投影上,点、直线在平面上,点和直线的正投影一定在该平面的正投影上,这种性质称为正投影的 () A.同素性 B .从属性 C .定比性 D .平行性
【单选题】Over the past fifteen years, the largely urbanized Northeastern United States has shown more and more the influence of the Southwestern portion of the country. Once, very few people in New York City c...
A.
The lifestyle. of people in the Northeast has been enriched by the influence of the Southwestern states.
B.
Most residents of the Southwestern states regularly eat at Tex-Mex restaurants.
C.
Over the last fifteen years, residents of the Southwestern United States have increasingly adopted lifestyles similar to those of the Northeast.
D.
Tex-Mex dishes are an element of the regional cuisine of the Southwestern states.
E.
People in the Northeastern United States eat out more frequently than they did fifteen years ago.
【单选题】According to Study 1 and Study 2, the crater floor of the volcano Pele has reflectances most similar towhich of the following S allotropes?
A.
White S
B.
Orange S
C.
Red S
D.
Brown S
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【判断题】直线倾斜于某投影面,则直线在该投影面上的正投影积聚为一点,平面倾斜于投影面,则平面在该投影面上的正投影积聚为一直线。
A.
正确
B.
错误
【单选题】直线在某投影面上的投影为一点,平面图形在某投影面上的投影为直线段,这体现了投影的()。
A.
积聚性
B.
定比性
C.
平行性
D.
不可逆性
【简答题】Chinese writer Mo Yan has won the 2012 Nobel Prize in Literature, announced the Swedish Academy in Stockholm on Thursday. The win makes Mo Yan the first Chinese citizen to win the Nobel in its 111-yea...
【简答题】Chinese writer Mo Yan has won the 2012 Nobel Prize in Literature, announced the Swedish Academy in Stockholm on Thursday.The win makes Mo Yan the first Chinese citizen to win the Nobel in its 111-year...
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