Fill in the gaps in the descriptions of the figures using the words from the table above where possible and the following verbs: break, free, move, come, occur.

• Figure 1 shows a part of a silicon crystal in which the breaking of covalent bonds is taking place.

• Was this caused by heating?

• Yes, by heating. In Figure 1 it is shown that one covalent bond … and an electron … itself. A hole … at point A.

Fig. 1. A hole has appeared at point A

• Will you be able to explain what is taking place in the next figure (Fig. 2)?

• Yes, of course. A hole … at point B and now two electrons can move through the crystal.

Fig. 2. A hole has appeared at point B

• Look at Fig. 3. The second electron … close enough to the first hole and is attracted by its electric field. Recombination … . Now there is no able already at point A. But still there is a hole at point B. The hole seems to … from position A to position B.

• Looking at this figure, it becomes clear that one more hole … at point C.

Fig. 3. Hole A has disappeared and hole C has

appeared

• As shown in Fig.4 the third free electron … through the crystal lattice. Again recombination … and a hole … . The effect is as though a hole … from point A to point C.

Fig. 4. Hole B has disappeared

1.How have you decreased the capacitance of your system?

I have just connected equal capacitors in series.

(I/just/connect/equal/capacitors/in series)

2. Can we observe any changes in the movement of electrons and holes?

Of course, we can, but …

(only/when/process/of recombination/already/occur)

3. Could you stop the movement of holes quite fast?

No, …

(I/just/heat/peace of silicon)

4. Have you already changed a random character of movement of holes in a piece of germanium?

Unfortunately …

(I/not/apply/any/voltage/yet)

5. Do you think me an expert in a problem of the movement of holes?

No, …

(We/already/consider/a lot of/important/things/but not all)

6. Could you increase the amplification factor of our circuit?

Yes, …

(I/already/replace/triode/to tetrode)