Нужно указать время данных глаголов. 1. But may also be ions when the conduction takes place in gaseous or liquid conductors, in which the ions are mobile. (be/takes) 2. A metal is made up of tiny crystals which are visible under a microscope. (is made/are visible) 3. An atom is a complex particle in which tiny electrons move around nucleus. (move) 4. Some of the electrons move freely between the atoms. (move) 5. There must be some driving force to cause the electrons to move through the metal conductor. (must be/to move) 6. This driving force tending to produce the motion of electrons through a circuit is called an electromotive force. (to produce) 7. When an electromotive force is applied to the ends of a wire the free electrons move in one direction. (is applied/move) 8. It is the movement of the free electrons in a conductor that induces an electric current. (the induces) 9. No one has ever seen analectic current. (seen) 10. We only know of the existence of a current by its effects. (know) 11. A current can heat a conductor, it can have a chemical action when passing through a solution, or it can produce a magnetic effect. (can heat/can have/can produce) 12. We can measure currents by observing their heating, their chemical, or their magnetic effects. (can measure/observing) 13. There are some kinds of current, namely. (are some)