A space in which a gas is rarefied is called a vacuum. And when the rarefaction is so great that a molecule of the remaining gas can fly from one wall of the vessel to the other without colliding with any other molecule along the way, they say there is a high vacuum in this vessel. Such a space with a rarefied gas is an interesting construction material for electricians.
When there are no electric charges in a high vacuum, it is a perfect insulator; the more electrically durable, the more perfect the vacuum. In a high vacuum, a gap between two metal electrodes of only 1 mm can withstand a voltage of over 100,000 volts.
Airless space is an ideal conductor for charged particles. Ions and electrons can fly enormous distances in a high vacuum without colliding with other particles and, therefore, without losing energy. This property of high vacuum is used in devices designed to accelerate charged particles to very high speeds. Such particles are used to bombard atomic nuclei to cause nuclear reactions. You can build a transformer with a secondary winding that has a very large number of turns. Moving along these turns, the electrons increase their energy. Eventually, it can become sufficient to attack the atomic nucleus. But this is not the most convenient way to attack.
You can place electrons or ions in a high vacuum and accelerate them there with electrical and magnetic forces until they gain speed many times greater than that which could be obtained on the highest-voltage transformer.
There is such a device - a betatron. This glass wheel has a vacuum inside, covering a steel core. A portion of electrons sent inside this wheel describes many hundreds of thousands of turns there, and with each revolution, electrical forces accelerate the electron bunch. And the electrons do not experience any resistance to movement. This device is a transformer without a secondary winding. But it acts like a transformer with hundreds of thousands of secondary turns. In a betatron, electrons can be accelerated as if they passed between electrodes with a voltage difference of tens of millions of volts. In this device, a high vacuum behaves like a material with zero resistance.
It has already been said that a vacuum can isolate electrodes with a very high voltage difference from each other. Electric motors and generators with vacuum insulation have been repeatedly proposed. Experimental models of such devices have even been built. In them, a vacuum is a material whose specific resistance equals infinity.
Transuranium elements following uranium, No. 93, 94, neptunium, and plutonium are unstable. This is nuclear "fuel". When split, they release energy. As construction materials, these elements are not yet used in pure form or compounds, and their use is not expected. Here, the term "linear" should not be understood in terms of extension. This electrical engineering, which obeys Ohm's law - the law of the straight line - can be both point and spatial.
In vacuum tubes, electrons go from a heated cathode to a positively charged anode. Depending on the design of the tube and its purpose, a wide variety of voltages - from fractions of a volt to hundreds of kilovolts - are applied to its electrodes, and a wide variety of currents - from microamperes to tens and hundreds of amperes - flow between them. It is customary to talk about the internal resistance of an electronic device. This resistance is the ratio of the applied volts to the received amperes. Sometimes, they take the ratio of the increment of the applied voltage to the increment of the received current. From units of ohms to many megohms - these can be the values of the internal resistance of various electronic devices. What an amazing material high vacuum is - its apparent resistivity can have any value from zero to infinity.
Vacuum has another interesting characteristic: resistance. When an electromagnetic wave propagates in a material,
the voltage in this wave to the current in it, or, what is the same, the ratio of the electric force in the wave to the magnetic force in it, is called wave resistance.
In high vacuum, this wave resistance is the same for electromagnetic waves of any length and current frequency and is equal to 376.6 Ohms. Only this resistance is completely different from the active resistance of all conductive materials. No power is lost on the wave resistance of the vacuum.
Wave resistance refers to the entire volume occupied by a plane wave. Suppose the voltage is specified in volts per 1 Ohm of wave space, and the current density per 1 cm2 must be determined. In that case, the wave resistance must be multiplied by 1/6 of the wavelength (approximately) and the volts divided by this product.
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