Boltzmann's constant. What is direct current? Parameters of direct current and voltage

Boltzmann's constant builds a bridge from the macrocosm to the microcosm, connecting temperature with the kinetic energy of molecules.

Ludwig Boltzmann is one of the creators of the molecular kinetic theory of gases, on which the modern picture of the relationship between the movement of atoms and molecules, on the one hand, and the macroscopic properties of matter, such as temperature and pressure, on the other, is based. In this picture, gas pressure is determined by the elastic impacts of gas molecules on the walls of the vessel, and temperature is determined by the speed of movement of the molecules (or rather, their kinetic energy). The faster the molecules move, the higher the temperature.

Boltzmann's constant makes it possible to directly relate the characteristics of the microworld with the characteristics of the macroworld - in particular, with thermometer readings. Here is the key formula that establishes this relationship:

1/2 mv 2 = kT

Where m And v— respectively, the mass and average speed of gas molecules, T is the gas temperature (on the absolute Kelvin scale), and k — Boltzmann's constant. This equation bridges the gap between the two worlds, linking the characteristics of the atomic level (on the left side) with volumetric properties(on the right side), which can be measured using human instruments, in this case thermometers. This connection is provided by the Boltzmann constant k, equal to 1.38 x 10 -23 J/K.

The branch of physics that studies the connections between the phenomena of the microworld and the macroworld is called statistical mechanics. There is hardly an equation or formula in this section that does not include Boltzmann's constant. One of these relationships was derived by the Austrian himself, and it is simply called Boltzmann equation:

S = k log p + b

Where S— entropy of the system ( cm. Second law of thermodynamics) p- so-called statistical weight(a very important element of the statistical approach), and b- another constant.

Throughout his life, Ludwig Boltzmann was literally ahead of his time, developing the foundations of the modern atomic theory of the structure of matter, entering into fierce disputes with the overwhelming conservative majority of the scientific community of his day, who considered atoms only a convention, convenient for calculations, but not objects of the real world. When his statistical approach did not meet with the slightest understanding even after the advent of the special theory of relativity, Boltzmann committed suicide in a moment of deep depression. Boltzmann's equation is carved on his tombstone.

Boltzmann, 1844-1906

Austrian physicist. Born in Vienna into the family of a civil servant. Studied at the University of Vienna on the same course with Josef Stefan ( cm. Stefan-Boltzmann law). Having defended his degree in 1866, he continued his scientific career, holding at different times professorships in the departments of physics and mathematics at the universities of Graz, Vienna, Munich and Leipzig. Being one of the main proponents of the reality of the existence of atoms, he made a number of outstanding theoretical discoveries that shed light on how phenomena at the atomic level affect the physical properties and behavior of matter.

Definition of DC current

Ideally, direct current does not change its value and direction over time. In reality, direct current is not a constant value in rectifier devices, since it contains a variable component (ripple).

Shape of DC components

In galvanic cells, direct current is also not constant, its value decreases across the load over time, thus, direct current is a conditional definition and when using it, changes in a constant value are neglected.

Direct current component (DC)

DC stands for Direct Current, translated as direct current. Graphically in the form of current you can see its changes over time or ripple. Such ripple occurs in the form of direct current in filtered rectifiers where small capacitances are used. In rectifier devices without the use of capacitors, the pulsation can be large.

The pulsating current at the output of a rectifier without capacitors is sometimes called pulsed current. The ripple current graph shows the DC component (straight line) and the AC component (ripple). The direct current component is defined as the average value of the current over a period.

AVG is the average value of the constant current. The alternating component of AC can be considered as the change in direct current relative to the average value. The ripple of the DC waveform is determined by the formula.

Where Iac is the average value of the alternating component of AC, Idc is the direct current component.

All of the above also applies to constant voltage.

DC current and voltage parameters

The intensity of the electric current is expressed as the number of charges moved over a period of time through the cross section of the conductor. One of the important parameters of direct current is the current value, which is measured in Amperes. The current intensity of 1 Ampere is to move a charge of one Coulomb for 1 second.

DC voltage is measured in Volts. DC voltage is the potential difference between two points in the same electrical circuit. Also important parameters for constant voltage are the ripple range and the ripple factor. The ripple range is the difference between the maximum ripple value and the minimum.

And the ripple coefficient is expressed in relation to the effective value of the alternating component (AC) of the current to the constant value of the component (DC). Also an important parameter of direct current is power P. Direct current power can be characterized by its operation over a certain period of time. Power is measured in Watts and determined by the formula:

According to this formula, the same power can be obtained at different currents and voltages.

• CONSTANT, -and I, -oh; -I am nen, -Yanna, -yanno.

  1. only full f. Continuous, unceasing. The constant concern of the party and government for the welfare of the people. Constant surveillance. □ - I can’t stand constant peace and aimless life. Chekhov, Verochka. - The creative thought of a Komsomol member must be in a state of eternal restlessness, on the path of constant quest. V. Belyaev, Old Fortress. || Always, ordinary. A regular visitor to the theater. Regular customers. □ - Seagulls are the favorite birds of sailors. They are our constant companions on our sea wanderings. Novikov-Surf, The Sea is Calling.

  2. only full f. Designed for the long term, not temporary. Permanent exhibition. Full time job. Permanent resident. □ [At the table] everyone knew their permanent place: everyone sat according to seniority. Gladkov, A Tale of Childhood. There is a telephone connection between the lighthouse and the radio station, and not temporary, but permanent, on poles. Kaverin, Two captains.

  3. Unchangeable in one's inclinations, habits, affections, etc. [Smirnov:] Have you ever seen a woman in your lifetime who was sincere, faithful and constant? Chekhov, Bear. || Characteristic of such a person. Everyone knew their hot, constant love. Gogol, Portrait.

  Standing army- a regular army maintained by the state in peacetime.
  Constant (specialist.) is a quantity that retains the same value in the question being studied.
  Constant capital (econ.) - part of the capital spent on the acquisition of means of production.
  D.C (physical) - electric current that does not change its direction and strength.

Source (printed version): Dictionary of the Russian language: In 4 volumes / RAS, Institute of Linguistics. research; Ed. A. P. Evgenieva. - 4th ed., erased. - M.: Rus. language; Polygraph resources, 1999;

What is the prism constant and where does it come from?

The passage of the light beam of an electronic rangefinder through a retroreflective tetrahedral prism (or reflector) occurs with a delay, due to the fact that the density of the prism material is much higher than the density of air. This delay causes the measured distance to increase. The error in the measured distance can be compensated for by a distance correction, which is automatically taken into account in the software of modern total stations. Also, to compensate for the delay, you can use a physical shift of the nodal point of the prism relative to the axis of the rod/prism holder, by the amount of error caused by this delay. The correction is determined by the size of the prism and the refractive index of the glass used. Standard corrections most often found in modern reflectors:

0

-17.5 mm

-30 mm

-34 mm

-40 mm

Nodal point offset. Reflector constant

The constant of the reflector (the prism system as a whole, including the structure of the prism itself, and the mounting system on the pole/trigger adapter) is determined by the position of the conditional center of the prism holder, which is located at the intersection of the longitudinal axis of the pole and the horizontal axis of rotation of the reflector, relative to the nodal point of the prism. At first glance, it seems that solving the problem of taking into account the constant is quite simple - you just need to shift the prism relative to the axis of the pole by an amount equal to the constant of the prism. However, prisms and holders that have a nodal point offset equal to the prism constant can cause angular measurement error when aiming at the top of the prism if the reflector is not at right angles to the line of sight (two figures below).

To reduce positioning errors, some SECO reflectors have a nodal point offset of -17.5/18 mm (for prisms with a diameter of 25 mm) or - 40 mm (for prisms with a diameter of 62 mm). Displacement of the nodal point minimizes errors caused by the deviation of the point of view from the axis. This design is most justified when working at short distances or with large differences in heights, in cases where the top or center of the prism is used for sighting. See the picture below.

Maximum measurement range per reflector

The signal reflected from the prism is used to calculate the distance from the instrument to the target. In this case, the maximum operating range of the light range finder is mainly influenced by two factors: the diameter of the prism and the deflection of the reflected beam. To increase the maximum measured distance, you can increase the diameter of the prism by installing a system of several reflectors on the point. You can also increase the measurement range if you accurately orient the reflector towards the instrument. If the deviation of the reflected beam is large, not the entire light beam will fall back onto the rangefinder receiving module, and the maximum measurement range will be reduced.

In general, the best measurement results are achieved when the front of the prism is positioned strictly perpendicular to the light beam coming from the instrument, causing it to be reflected parallel. Unfortunately, during field work it is very difficult to perfectly align the prism relative to the instrument.

Beam deflection can also occur if the quality of the prism block is not high enough. This situation is typical when working at the maximum range of the rangefinder (the maximum range depends on the model and manufacturer of the equipment). In standard Seco reflectors, the accuracy of the prism block is such that the deviation of the reflected beam does not exceed 5 arc seconds. Higher precision prisms are also available for precision work.

Prism system assembly accuracy

The accuracy of the reflector is also affected by the position of the prism block in the housing and the position of the housing relative to the holder. The positioning accuracy of parts relative to each other in SECO reflective systems is less than 1 mm.

SECO uses the ZYGO GPI-XP/D interferometer to check the amount of prism beam deflection and ensure compliance with standards. Certificate of conformity is available upon additional request. Contact us for more information.

“The article was written based on materials from Seco. Original article in English can be found on Surveying.com and in Seco's printed and electronic documents."