G azərbaycan respublikasi təHSİl naziRLİYİ azərbaycan texniKİ universiteti M. M. QƏNDİLova e. Q. İsmayilova

Triode Constant
The families of triode characteristics, whish show the characteristic performances of each type of tube are not a result of accident. Rather they represent the outcome of purposeful design to make each tube behave in a curtain manner. The design factors of the tube are summarized by a series of numbers, called the tube constants. The three most important constants are the amplification factor, the ac plate resistance and the transconductance.

The amplification factor of triode is a measure of the relative effectiveness of the control grid in overcoming the electrostatic field produces by the plate. To determine the amplification factor it is necessary to change the plate voltage by a certain amount, record the change in plate current and then change the grid voltage by an amount just sufficient to restore the previous plate-current value. By comparing the plate-voltage change to the grid voltage change for the same change in plate current we can determine their relative effectiveness, which is the amplification factor.

The plate resistance describes the internal resistance of the tube for the flow of alternating plate current, when varying voltage is applied to the electrodes. The ac plate resistance is defined as the radio of a small change in plate voltage to he change in plate current produced thereby, when the grid voltage is kept at a constant value.

A third constant used in describing the properties of electron tubes is the control grid-to-plate transconductance designated by the symbol S. Transconductance is the most important of the tube constants, since it reveals the effectiveness of the control grid in securing changes in the plate current.

Crystals
Speaking about crystals one often imagines something beautiful, perfect and rare. In reality all solid bodies around us are crystals. The exceptions are plants, animals, water and the atmosphere.

Crystals offer a simple way for transforming one kind of energy into anther. It is possible to illuminate a crystal with red light and make it emit green rays. In fact, in modern technology all the instruments that can emit energy are built around crystals.

We know how to grow very thin crystals, which have a diameter of a few microns. Now it is necessary to grow artificially not only the crystals that do not exist in nature, but those that exist but are not enough.

Rock crystals, for instance is grown at factories.

Ruby crystals, too, have numerous applications. Artificial rubies and sapphires go into all watches and other instruments. Having received a few dozens of crystals from nature, technology is now producing something like a thousand different varieties. The future of crystals and their application in industry is full of great promise.

Of special interest is research into the strength of crystals. All metals and alloys constitute a collection of variously placed tiny crystals. The more perfect the crystals, the higher the strength of the metal. This means that by special methods it is possible to obtain crystals of required strength.

Already, now we know how to grow very thin crystals, which have a diameter of a few microns only and possess extraordinary high tensile strength.

Ruby crystals, too, have numerous applications. Artificial rubies and sapphires go into most watches and other instruments.