以it 做形式主语，而把真正的主语放到后面，这是
英语特有的一种句型，也是科技
英语中常见的一种句型。这种句型的译法既是千姿百态的同时又是有规律可循的。概括地说，有下列几种译法：
译成汉语不定人称句
In the United States the customary voltage for household use has become 110-120 V since it was discovered that higher voltages could cause fatal accidents.美国通常的家用电压是110-120伏，因为人们发现，更高的电压会造成致命的事故。
We have already observed that for a long time it was incorrectly believed that current flowed from positive to negative.我们已经观察到，人们过去长期错误地认为电流是由正极流向负极的。
译成无人称句
It is obvious that resistance is responsible for heating and lighting effects of many common household appliances.很明显，许多家庭常用电器设备的加热和照明作用都依靠电阻。
It may be safely said that many other materials besides amber could be charged by rubbing.可以有把握地说，除了琥珀意外，许多其他物质通过摩擦也能带电。
把that从句、动词不定式等译成真实主语
It is important to realize the two points about forging and pressing.弄清锻压的这两个要点是重要的。
It is quite remarkable that so much of this rapid development of electrical devices and the resulting industry took place during the nineteenth century, when the nature of electricity was not completely understood.电力装置以及由此而兴起的工业的这一迅速发展主要发生在19世纪，而当时人们对电的性质还不完全了解，这是十分值得注意的。
主表倒译
即将作真正主语的从句或动词不定式译成表语，原表语译成主语。
It is desirable to use large units for measurement of large quantities and small units for small quantities.最好是用大的单位来测量大的量值，用小的单位来测量小的量值。
It is a matter of common experience that it is much easier to roll bodies along than to slide them.通常的经验是物体想前滚动比向前滑动容易得多。
It is noteworthy that small as atoms are, they contain vast amounts of energy.值得注意的是原子随小，却具有很大的能量。
把形式主语it和它的谓语译成一个短语，把从句译成句子的主干
It goes without saying that these waves travel at the speed of light.显然，这些波是以光速传播的。
It follows that radar is an electronic system for locating aircraft or cloud patterns.由此可见，雷达是用来测定飞机位置或云型位置的电子系统。
