题目内容
若电刷放置在几何中性线上，以下关于他励直流发电机和并励直流发电机的外特性的描述正确的是（）。A、B、C、D、
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并励直流发电机的自励条件是：发电机的磁路中应有，且其方向应和励磁磁动势（选填：相同；相反），另外励磁回路的总电阻必须（选填：大于；等于；小于）临界电阻。
直流电机电磁转矩公式中的电枢电流Ia等于导体电流乘以并联支路对数。（）
直流电机电枢绕组有两种基本型式：绕组和绕组。
Directions: In this section, there is a passage with ten blanks. You are required to select one word for each blank from a list of choices given in a word bank following the passage. Read the passage through carefully before making your choices. Each choice in the bank is identified by a letter. Please mark the corresponding letter for each item on Answer Sheet 2 with a single line through the centre. You may not use any of the words in the bank more than once.Questions 1 to 10 are based on the following passage.Just because they can’t sing opera or ride a bicycle doesn’t mean that animals don’t have culture. There’s no better example of this than killer whales. As one of the most__1__predators（食肉动物），killer whales may not fit the__2__of a cultured creature. However, these beasts of the sea do display a vast range of highly__3__behaviors that appear to be driving their genetic development.The word “culture” comes from the Latin “colere,” which__4__means “to cultivate.” In other words, it refers to anything that is__5__or learnt, rather than instinctive or natural. Among human populations, culture not only affects the way we live, but also writes itself into our genes, affecting who we are. For instance, having spent many generations hunting the fat marine mammals of the Arctic, the Eskimos of Greenland have developed certain genetic __6__ that help them digest and utilize this fat-rich diet, thereby allowing them to __7__ in their cold climate.Like humans, killer whales have colonized a range of different __8__ across the globe, occupying every ocean basin on the planet, with an empire that __9__ from pole to pole. As such, different populations of killer whales have had to learn different hunting techniques in order to gain the upper hand over their local prey（猎物）. This, in turn, has a major effect on their diet, leading scientists to __10__ that the abilitytolearn population-specific hunting methods could be driving the animals’ genetic development.A)acquiredB) adaptationsC) brutalD) deliberatelyE) expressedF) extendsG) habitatsH) humbleI) imageJ) litereallyK) refinedL) revolvesM) speculateN) structureO) thrive
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