Temperature units converter, calculator

The basic unit of temperature measurement is the degree of the International Temperature Scale, which is nearly equivalent to the degree Celsius. This unit represents 1/100 of the temperature interval between 0 °C and 100 °C, corresponding to the melting point of ice and the boiling point of water at a pressure of 760 mm Hg.

 

Absolute temperature is estimated from absolute zero, which is -273.16 °C, and is expressed in degrees Kelvin (K). The degree Kelvin is equal in magnitude to the degree Celsius. Therefore, absolute temperature can also be expressed in degrees of the Celsius scale as follows:

 

T, °K = t, °C + 273.16

 

In the SI system, the degree Kelvin is established as the temperature measurement unit. It is permissible to use degrees Celsius along with degrees Kelvin to express practical results of temperature measurements, depending on the starting point (zero position) on the scale.

 

Example: 250±5 °C = 523.16±5 °K.

 

Molten steel glows with a blinding white heat. It is heated to 1,500° C. The temperature on the surface of the Sun is about 6,000° C. All substances at this temperature are in a gaseous state. Is it possible to create a temperature on Earth that is tens of times higher than the visible temperature of the Sun's surface?

 

Yes, it is possible. And with very simple means. In many electrical devices, the structural materials in operation have a temperature of tens of thousands of degrees. They withstand this temperature not for short moments but for a long time: hours, months, and years. Many of us have observed the operation of these devices, not knowing about their cosmic temperatures. A substance with a temperature of tens of thousands of degrees is inside cold glass or metal vessels. This red-hot substance has another interesting property - 1 m3 often weighs less than 1 g. It is easy to guess what material we are talking about. A cubic meter of air at atmospheric pressure and 0° C weighs 1.29 kg, while a cubic meter of highly rarefied gas can weigh less than 1 g.

 

Rarefied gases and metal vapors are used as current conductors in ionic devices. The vacuum inside ionic devices is low, not as great as in devices with a pure electron discharge.

 

When an electron moves in an ionic device, it encounters gas atoms. The electron collides with them, knocks electrons out of them, and turns these atoms into charged ions. That is why these devices are called ionic - in their discharge space, in addition to electrons, there are always ions. Ionic devices include gas-discharge lamps, mercury converters, and many others. All bodies' molecules are in constant motion, and temperature measures this energy, the energy of tireless chaotic motion. In air, for example, at 20° C, nitrogen and oxygen molecules have an average speed of several hundred meters per second. The concept of "temperature" can be applied not only to a collection of neutral molecules but also to a collection of electrons and ions if only these charged particles move as chaotically as molecules in a gas, like midges over a pond in calm weather.

 

The action of electrical forces can give a charged particle speed. The greater the voltage difference a charged particle passes through, the greater the speed it will acquire and the more energy it will accumulate. When the charge of a particle is equal to the charge of an electron, having passed a voltage difference of only 1 V, it will have the same energy reserve as an atom of gas heated to a temperature of about 7,500 ° C. At room temperature, an atom of gas has an average energy of less than four-hundredths of an electron volt.

 

If a cluster of electrons and ions is accelerated to an average voltage of 10 V, then this cluster must be assigned a temperature of 75,000 ° C.

A mixture of electrons and ions in a rarefied gas is called plasma. It is formed when a sufficiently large current passes through the gas. Electrons enter the plasma from the cathode at speeds of up to several tens of volts. Electrons that have lost speed are extracted from the plasma by the anode. Ions are constantly formed in the plasma due to electrons colliding with neutral atoms. Some atoms become excited under the impact of electrons and then emit their excess energy through light radiation. Electrons, ions, and neutral atoms constantly collide with each other in the plasma and exchange energy. But electrical forces continually disturb the established equilibrium. Therefore, different particles in the plasma move at different speeds and have different energy reserves. Electrons have the highest speed, energy, and, thus, the highest temperature. The temperature of the electron gas is tens of thousands of degrees. Ions have a lower average energy, so their cluster has a lower temperature. Neutral atoms are in the plasma at an even lower temperature. Finally, there is a fourth temperature — the temperature of the vessel's walls containing the ionized gas. This is the weakest of all temperatures associated with the ion discharge.

In a steam boiler, the highest temperature is in the firebox, the walls of the steel tubes are lower, and the temperature of the water inside the tubes is even lower. Different temperatures are in zones remote from each other. In ion plasma, particles with different energies (temperatures) are closely mixed.
 

When the gas density is low, the temperature difference between clusters of electrons, ions, and neutral atoms is large.

Red and blue advertising lights burn above subway entrances, near movie theaters and restaurants. Neon or argon is in glass tubes at a pressure of less than 1/100 of the atmosphere. The density of the gas inside the discharge tubes is low. The electron gas here has a temperature of tens of thousands of degrees, and the gas of neutral atoms is only hundreds of degrees.

The higher the density of the gas in which the electric discharge occurs, the more collisions with neutral atoms the electrons and ions undergo during their movement in the discharge space. The closer the temperatures of the ion, electron, and neutral gases become to each other, the closer they become.

 

In an electric arc that burns at atmospheric pressure, the temperature of the electron and ion gases is several thousand degrees, and the neutral gas temperature is slightly less. Doesn't it sound strange that in an arc that melts and burns the most heat-resistant materials, the ions and electrons are "colder" than in a gas-discharge tube, the glass cylinders of which are slightly warm? In the lightning discharge channel, the temperature of the electron and ion gases is less than in the bluish cloud that is visible between the cathode and anode of the gastrin. In electron-ion plasma, the high temperature of clusters of individual particles is combined with their very low concentration. The total amount of energy in a unit volume of plasma is negligible.