句子成分的强调手段（2）
(2) 强调宾语（不多见） It is the north pole(北极) of a bar magnet(条形磁铁) which the lines of force(磁力线) leave(离开). It is the flow(流动) of electrons(电子), not the electrons themselves that we call an electric current(电流). It is the losses(损耗) caused(引起) by friction(摩擦) that we must try(力图) to overcome(克服) by various means(各种方法).
(3)强调状语 It is when lines of force(磁力线) are being cut(切割) by the wire(导线) that an emf(电动势) is induced(感应) in it. It is with the hope of giving the reader(读者) an insight into(了解) the principle(原理) by which electronic instruments(电子仪器) function(工作) that this book has been written. It is to observe(观察) the earth that satellites(卫星) carry(带) TV cameras(摄像机) far into space(太空).
It is appropriate(合适的) to ask(问) why it is that alpha particles(阿尔法粒子) are given off(发射) by heavy nuclei(重原子核). It is not clear(清楚的) yet(尚) under what conditions(条件) it is that this method(方法) may be used. It must have been much later(很久以后) that Man learned(学会) to cook food(烧煮食物) by heating(加热) it with boiling water(开水) or with steam(蒸汽). 注意：下面两句中的“when”和“where”均应该改成“that”。
It was just 50 years ago when Tom Watson, the founder(创始人) of IBM, proclaimed(声称) that the world couldn’t possibly(可能) need(需要) more than five computers. It was in that laboratory where they found a strange phenomenon(奇怪的现象).
(4) 强调介词宾语（不常见） However, it is just this distinction(特性) with which the second law(定律) of thermodynamics(热力学) is concerned (涉及). （本句也可写成：However, it is just this distinction which [或that] the second law of thermodynamics is concerned with.） It is the nurse(护士) with whom the patients(病人) spend(度过) most of the time in a ward room(病房). （本句也可写成：It is the nurse who [或：that] the patients spend most of the time in a ward room with.）