Temperature coefficient of metal resistance. Temperature coefficient. Heat and cold in electronics Temperature coefficient of semiconductors

WHAT IS the temperature coefficient of resistance of METAL - it is. Brief DEFINITION OF THE CONCEPT OF TKS.

Answer to the question: THE CONCEPT OF TKS, DEFINITION OF WHAT IS THE temperature coefficient of electrical resistance of METAL - THIS IS the ratio of the relative change in the electrical resistance of METAL to the change in temperature by one unit. The units of temperature are degrees Kelvin (Kelvins) or degrees Celsius. It is this definition of the concept of TKS that we most often find in reference and educational literature. The definition is quite understandable and, it seems to me, quite clearly reflects the essence of the concept.

HOW IS THE TEMPERATURE COEFFICIENT OF METAL RESISTANCE DETERMINED - HOW TO CALCULATE, FORMULA FOR CALCULATING TCR.

Answer to the question: HOW IS THE temperature coefficient of electrical resistance of METAL DETERMINED?, its value can be calculated mathematically, based on physical experiment data or reference, tabular values ​​of the electrical resistance of ZINK at different temperatures. To independently determine using the formula, you can use the TCS calculation formula given below.

α = (R1 - R2) / R1 X (T1 - T2).

1. R1 - value: electrical resistance at initial temperature.
2. R2 - value: electrical resistance at a changed temperature.
3. T1 - value: initial temperature.
4. T2 - value: changed temperature.
5. (R1 - R2) - value: difference in electrical resistance.
6. (T1 - T2) - value: temperature difference.

WHAT IS THE METAL temperature coefficient of resistance MEASURED IN - UNITS OF MEASUREMENT TKS.

Answer to the question: WHAT IS THE temperature coefficient of electrical resistance of METAL measured in?. The generally accepted units for measuring TCS are Kelvin. More precisely, Kelvin degrees taken to the minus 1 power: K -1. Less commonly, we can find other units of measurement of TKS. Which? Also degrees, but Celsius. In practice, in reference books and reference tables, the data in which the value of the resistance coefficient is measured, for the convenience of expressing measurements of the physical quantity of the TCS, are given and indicated as the ratio: 10 -3 /K. There is a universal formula that helps to understand how the value of the electrical resistance coefficient is measured, derived from the physical meaning of the concept. And taking into account the possibility of choosing any degrees to evaluate the value. See the formula for determining the units of electrical resistance coefficient below.

TKS = 1 Ohm / 1 Ohm X 1 Degree. Which in turn comes down to the ratio: TKS = Degree -1

As we can see from the formula, to determine the value (in general), you can use any degrees, for example: degrees Celsius (°C), degrees Fahrenheit (°F) or degrees Kelvin (K, outdated designation °K).

HOW IS THE TEMPERATURE COEFFICIENT OF METAL RESISTANCE INDICATED - what letter or symbol is TKS INDICATED.

Answer to the question: HOW IS THE temperature coefficient of electrical resistance of METAL?. The physical quantity TCS is most often denoted by a letter of the Greek alphabet, like many other quantities (values) in physics. The letter alpha - α was chosen as the symbol to denote the resistance coefficient. If necessary, a more extended notation can be used. For example: indicate next to α additional information reflecting the type of substance, in our case it is α(metallum). Or indicate when designating the temperature at which this coefficient of electrical resistance operates. Most often we are interested in TCS under so-called NORMAL CONDITIONS. Which implies a temperature of 20° C. This designation looks something like this: α(20° C).

PHYSICAL MEANING of the temperature coefficient of resistance of METAL.

Answer to the question: PHYSICAL MEANING of the temperature coefficient of electrical resistance of METAL. The physical meaning of the term usually means that the resistance coefficient α reflects the change in the resistance of the METAL (ITS DYNAMICS). Roughly speaking, this is a kind of gradient. Which shows how much (how many times, by what amount) the electrical resistance will change (and it can either decrease or increase) when the temperature changes by one unit (degree). Please note that TCS (α) is a dynamic characteristic of the electrical properties of METAL.

Table 1. Temperature coefficient of electrical resistance of METAL.

The electrical resistance of a conductor generally depends on the material of the conductor, its length and cross-section, or more briefly, on the resistivity and geometric dimensions of the conductor. This dependence is well known and is expressed by the formula:

Everyone knows and, from which it is clear that the lower the current, the higher the resistance. Thus, if the resistance of the conductor is constant, then with increasing applied voltage the current should increase linearly. But in reality this is not the case. The resistance of conductors is not constant.

You don't have to look far for examples. If you connect a light bulb to an adjustable power supply (with a voltmeter and ammeter), and gradually increase the voltage on it, bringing it to the nominal value, then it is easy to notice that the current does not grow linearly: as the voltage approaches the nominal value of the lamp, the current through its spiral grows more and more slowly, and the light bulb glows brighter.

There is no such thing that with a doubling of the voltage applied to the spiral, the current also doubles. Ohm's law doesn't seem to apply. In fact, Ohm's law is true, and exactly, the resistance of the lamp filament is not constant, it depends on temperature.

Let us remember what is associated with the high electrical conductivity of metals. It is associated with the presence in metals of a large number of charge carriers - components of the current -. These are electrons formed from the valence electrons of metal atoms, which are common to the entire conductor; they do not belong to each individual atom.

Under the influence of an electric field applied to a conductor, free conduction electrons move from chaotic to more or less ordered movement - an electric current is formed. But electrons on their way encounter obstacles, inhomogeneities of the ionic lattice, such as lattice defects, inhomogeneous structure caused by its thermal vibrations.

Electrons interact with ions, lose momentum, their energy is transferred to the lattice ions, turns into vibrations of the lattice ions, and the chaos of the thermal movement of the electrons themselves intensifies, which is why the conductor heats up when current passes through it.

In dielectrics, semiconductors, electrolytes, gases, non-polar liquids, the cause of resistance may be different, but Ohm's law, obviously, does not always remain linear.

Thus, for metals, an increase in temperature leads to an even greater increase in thermal vibrations of the crystal lattice, and the resistance to the movement of conduction electrons increases. This can be seen from the experiment with the lamp: the brightness of the glow increased, but the current increased less. That is, the change in temperature affected the resistance of the lamp filament.

As a result, it becomes clear that the resistance depends almost linearly on temperature. And if we take into account that when heated, the geometric dimensions of the conductor change slightly, then the electrical resistivity depends almost linearly on temperature. These dependencies can be expressed by the formulas:

Let's pay attention to the coefficients. Let the resistance of the conductor at 0°C be equal to R0, then at a temperature t°C it will take the value R(t), and the relative change in resistance will be equal to α*t°C. This proportionality coefficient α is called temperature coefficient of resistance. It characterizes the dependence of the electrical resistance of a substance on its current temperature.

This coefficient is numerically equal to the relative change in the electrical resistance of the conductor when its temperature changes by 1K (one degree Kelvin, which is equivalent to a temperature change by one degree Celsius).

For metals, the TCR (temperature coefficient of resistance α), although relatively small, is always greater than zero, because when current passes, electrons collide more often with ions of the crystal lattice, the higher the temperature, that is, the higher their thermal chaotic movement and the higher their speed. Colliding in chaotic motion with lattice ions, the electrons of the metal lose energy, which is what we see as a result - the resistance increases when the conductor is heated. This phenomenon is used technically in.

So, temperature coefficient of resistance α characterizes the dependence of the electrical resistance of a substance on temperature and is measured in 1/K - kelvin to the power of -1. The value with the opposite sign is called the temperature coefficient of conductivity.

As for pure semiconductors, the TCR is negative for them, that is, the resistance decreases with increasing temperature, this is due to the fact that as the temperature rises, more and more electrons move into the conduction band, and the concentration of holes also increases. The same mechanism is characteristic of liquid non-polar and solid dielectrics.

Polar liquids sharply decrease their resistance with increasing temperature due to a decrease in viscosity and an increase in dissociation. This property is used to protect electronic tubes from the destructive effects of high inrush currents.

For alloys, alloyed semiconductors, gases and electrolytes, the thermal dependence of resistance is more complex than for pure metals. Alloys with very low TCR, such as manganin and constantan, are used in.

The results of resistivity measurements are greatly influenced by shrinkage cavities, gas bubbles, inclusions and other defects. Moreover, Fig. 155 shows that small amounts of impurity entering the solid solution also have a large effect on the measured conductivity. Therefore, it is much more difficult to produce satisfactory samples for measuring electrical resistance than for

dilatometric study. This led to another method of constructing phase diagrams, in which the temperature coefficient of resistance is measured.

Temperature coefficient of resistance

Electrical resistance at temperature

Matthiessen found that the increase in metal resistance due to the presence of a small amount of the second component in the solid solution does not depend on temperature; it follows that for such a solid solution the value does not depend on the concentration. This means that the temperature coefficient of resistance is proportional, i.e., conductivity, and the graph of the coefficient a depending on the composition is similar to the graph of the conductivity of a solid solution. There are many known exceptions to this rule, especially for transition metals, but for most cases it is approximately true.

The temperature coefficient of resistance of intermediate phases is usually of the same order of magnitude as for pure metals, even in cases where the connection itself has high resistance. There are, however, intermediate phases whose temperature coefficient in a certain temperature range is zero or negative.

Matthiessen's rule applies, strictly speaking, only to solid solutions, but there are many cases where it appears to be true also for two-phase alloys. If the temperature coefficient of resistance is plotted against composition, the curve usually has the same shape as the conductivity curve, so the phase transformation can be detected in the same way. This method is convenient to use when, due to fragility or other reasons, it is impossible to produce samples suitable for conductivity measurements.

In practice, the average temperature coefficient between two temperatures is determined by measuring the electrical resistance of the alloy at those temperatures. If no phase transformation occurs in the temperature range under consideration, then the coefficient is determined by the formula:

will have the same meaning as if the interval is small. For hardened alloys as temperatures and

It is convenient to take 0° and 100°, respectively, and the measurements will give the phase region at the quenching temperature. However, if measurements are made at high temperatures, the interval should be much less than 100°, if the phase boundary may be somewhere between the temperatures

Rice. 158. (see scan) Electrical conductivity and temperature coefficient of electrical resistance in the silver-magic system (Tamman)

The great advantage of this method is that the coefficient a depends on the relative resistance of the sample at two temperatures, and is thus not affected by pitting and other metallurgical defects in the sample. Conductivity and temperature coefficient curves

resistances in some alloy systems repeat one another. Rice. 158 is taken from Tammann's early work (the curves refer to silver-magnesium alloys); later work showed that the region of the -solid solution decreases with decreasing temperature and a superstructure exists in the region of the phase. Some other phase boundaries have also undergone changes recently, so that the diagram presented in Fig. 158 is of historical interest only and cannot be used for accurate measurements.

Probably everyone knows. In any case, we have heard about him. The essence of this effect is that at minus 273 °C the conductor’s resistance to the flowing current disappears. This example alone is enough to understand that there is a dependence on temperature. A describes a special parameter - the temperature coefficient of resistance.

Any conductor prevents current from flowing through it. This resistance is different for each conductive material; it is determined by many factors inherent in a particular material, but this will not be discussed further. Of interest at the moment is its dependence on temperature and the nature of this dependence.

Metals usually act as conductors of electric current; their resistance increases as the temperature increases, and decreases as the temperature decreases. The magnitude of such a change per 1 °C is called the temperature coefficient of resistance, or TCR for short.

The TCS value can be positive or negative. If it is positive, then it increases with increasing temperature; if it is negative, then it decreases. For most metals used as conductors of electric current, the TCR is positive. One of the best conductors is copper; the temperature coefficient of resistance of copper is not exactly the best, but compared to other conductors, it is less. You just need to remember that the TCR value determines what the resistance value will be when the environmental parameters change. The greater this coefficient, the more significant its change will be.

This temperature dependence of resistance must be taken into account when designing electronic equipment. The fact is that the equipment must operate under any environmental conditions; the same cars are operated from minus 40 °C to plus 80 °C. But there are a lot of electronics in a car, and if you do not take into account the influence of the environment on the operation of circuit elements, you may encounter a situation where the electronic unit works perfectly under normal conditions, but refuses to work when exposed to low or high temperatures.

It is this dependence on environmental conditions that equipment developers take into account when designing it, using the temperature coefficient of resistance when calculating circuit parameters. There are tables with TCR data for the materials used and calculation formulas, according to which, knowing the TCR, you can determine the resistance value under any conditions and take into account its possible change in the operating modes of the circuit. But to understand TKS, now neither formulas nor tables are needed.

It should be noted that there are metals with a very small TCR value, and they are used in the manufacture of resistors, the parameters of which are weakly dependent on environmental changes.

The temperature coefficient of resistance can be used not only to take into account the influence of fluctuations in environmental parameters, but also for which, knowing the material that was exposed, it is enough to use the tables to determine what temperature the measured resistance corresponds to. An ordinary copper wire can be used as such a meter, although you will have to use a lot of it and wind it in the form of, for example, a coil.

All of the above does not fully cover all issues of using the temperature coefficient of resistance. There are very interesting application possibilities associated with this coefficient in semiconductors and electrolytes, but what is presented is sufficient to understand the concept of TCS.

Per unit.

The temperature coefficient of resistance characterizes the dependence of electrical resistance on temperature and is measured in kelvins to the minus first power (K ​​−1).

The term is also often used "temperature coefficient of conductivity". It is equal to the inverse value of the resistance coefficient.

Temperature dependence of metal resistance alloys, gases, doped semiconductors And electrolytes is more complex.

Wikimedia Foundation. 2010.

• Kornyakt Palace
• The Private Life of Sherlock Holmes (film)

See what “Temperature coefficient of electrical resistance” is in other dictionaries:

temperature coefficient of electrical resistivity of conductor material- The ratio of the derivative of the electrical resistivity of a conductor material with respect to temperature to this resistance. [GOST 22265 76] Topics: conductor materials... Technical Translator's Guide

Temperature coefficient of electrical resistivity of conductor material- 29. Temperature coefficient of electrical resistivity of a conductor material The ratio of the derivative of the electrical resistivity of a conductor material with respect to temperature to this resistance Source: GOST 22265 76:… …

GOST 6651-2009: State system for ensuring the uniformity of measurements. Resistance thermal converters made of platinum, copper and nickel. General technical requirements and test methods- Terminology GOST 6651 2009: State system for ensuring the uniformity of measurements. Resistance thermal converters made of platinum, copper and nickel. General technical requirements and test methods original document: 3.18 thermal reaction time ... Dictionary-reference book of terms of normative and technical documentation

GOST R 8.625-2006: State system for ensuring the uniformity of measurements. Resistance thermometers made of platinum, copper and nickel. General technical requirements and test methods- Terminology GOST R 8.625 2006: State system for ensuring the uniformity of measurements. Resistance thermometers made of platinum, copper and nickel. General technical requirements and test methods original document: 3.18 thermal reaction time: Time ... Dictionary-reference book of terms of normative and technical documentation

Resistance thermometer- Conventional graphic designation of a resistance thermometer A resistance thermometer is an electronic device designed to measure temperature and based on the dependence of electrical resistance ... Wikipedia

Resistance thermometer- a device for measuring temperature (See Temperature), the principle of operation of which is based on a change in the electrical resistance of pure metals, alloys and semiconductors with temperature (on an increase in resistance R with increasing ... ...

Aluminum- (Aluminum) Alloys and production of aluminum, general characteristics of Al. Physical and chemical properties of aluminum, production and occurrence of Al in nature, application of aluminum Contents Contents Section 1. Name and history of the discovery. Section 2. General... ... Investor Encyclopedia

Thermal flow meter- Thermal flow meter is a flow meter in which the effect of heat transfer from a heated body by a moving medium is used to measure the flow rate of a liquid or gas. There are calorimetric and hot-wire flowmeters. Contents 1... ...Wikipedia

Aluminum- 13 Magnesium ← Aluminum → Silicon B Al ↓ Ga ... Wikipedia

Iron- (Latin Ferrum) Fe, a chemical element of group VIII of the periodic system of Mendeleev; atomic number 26, atomic mass 55.847; shiny silvery white metal. The element in nature consists of four stable isotopes: 54Fe (5.84%),... ... Great Soviet Encyclopedia