题目内容（请给出正确答案）

[主观题]

An independent voltage source is a , which maintains a specified voltage between its terminals.

A、one-terminal element

B、two-terminal element

C、three-terminal element

D、four-terminal element

提问人：网友wishishiren 发布时间：2022-01-07

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第6题

材料：

The field current supply in older machines comes from a lower voltage direct current generator or exciter on the same shaft as the alternator. Modern machines however are either statically excited or of the high-speed brush-less type. The exciter is required to operate to counter the effects of power factor for a given load. The power factor is a measure of the phase difference between voltage and current and is expressed as the cosine of the phase angle. With a purely resistance load the voltage and the current are in phase, giving a power factor of one. The power consumed is therefore the product of voltage and current. Inductive or capacitive loads, combined with resistance loads, produce lagging or leading power factors which have a value less than one.

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第7题

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