Put the verb in brackets into the correct form, Present Continuous or Present Simple

1. This scientist (to be) never satisfied. He always (to complain).

2. In a vacuum-tube triode there (to be) three electrodes: a cathode, a plate and a grid.

3. When heated the cathode (to emit) electrons.

4. I see in Fig.1 that the electrons (to flow) from the cathode to the plate.

5. The grid (to control) the flow of electrons when the device is switched on.

6. The closer the grid (to be) to the cathode, the more influence it has on the electron flow.

7. Look! The plate current (to decrease).

8. We are decreasing the negative voltage on the grid to 8 volts, and the current gradually (to increase).

9. Due to this property of a triode, it (can) be usedfor amplification.

10. Usually he (to work) as a software maker, but he (to read) lectures now.

11. The number of electrons (to increase) very rapidly in this device.

12. It (to get) late. Let’s finish the experiment.

13. The grid (to be) placed between the cathode and the plate.

14. A: You (to work) hard today. B: Yes, I have a lot to do.

15. Even if a small negative voltage is applied to the grid, this (to result) in a large plate current.