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问题 单项选择题

电力系统谐波产生的根本原因是（）

A.由于电力系统中某些设备和负荷的非线性特性，即所加的电压与产生的电流不成线性（正比）关系而造成的波形畸变

B.电网中的操作引起过电压

C.电网中的故障产生的电压和电流的非线性

D.雷击过电压

答案

参考答案：A

问答题

Part 1


·A TV station is planning to develop a new program of talk show, hence some guests are needed. Guests for the talk show program should be:
☆ Good at using verbal and non-verbal devices, communicative.
☆ They also should have experience with certain significance in some way to themselves.
☆ You are asked to draw a copy to get guests.
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单项选择题

已知某地每小时最大降雨量为H=145mm/h，落水管径D=10cm，则每个落水管允许集水面积为( )。

A．30.2m2

B．620.6m2

C．62.06m2

D．302.07m2
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