Physical quantities. Measurement of physical quantities - Knowledge Hypermarket. What can be measured with a multimeter There are several subtypes of different calipers depending on the size, design features and principle of operation

What does it mean to measure a physical quantity? What is a unit of physical quantity called? Here you will find answers to these very important questions.

1. Let's find out what is called a physical quantity

For a long time, people have used their characteristics to more accurately describe certain events, phenomena, properties of bodies and substances. For example, when comparing the bodies that surround us, we say that the book is smaller than bookshelf, and the horse is larger than the cat. This means that the volume of the horse is greater than the volume of the cat, and the volume of the book is less than the volume of the cabinet.

Volume is an example of a physical quantity that characterizes the general property of bodies to occupy one or another part of space (Fig. 1.15, a). At the same time numeric value the volume of each body individually.

Rice. 1.15 To characterize the property of bodies to occupy one or another part of space, we use the physical quantity volume (o, b), to characterize movement - speed (b, c)

A general characteristic of many material objects or phenomena, which can acquire individual meaning for each of them, is called physical quantity.

Another example of a physical quantity is the familiar concept of “speed”. All moving bodies change their position in space over time, but the speed of this change is different for each body (Fig. 1.15, b, c). Thus, in one flight, an airplane manages to change its position in space by 250 m, a car by 25 m, a person by I m, and a turtle by only a few centimeters. That's why physicists say that speed is a physical quantity that characterizes the speed of movement.

It is not difficult to guess that volume and speed are not all the physical quantities that physics operates with. Mass, density, force, temperature, pressure, voltage, illumination - this is only a small part of those physical quantities, which you will become familiar with while studying physics.

2. Find out what it means to measure a physical quantity

In order to quantitatively describe the properties of any material object or physical phenomenon, it is necessary to establish the value of the physical quantity that characterizes this object or phenomenon.

The value of physical quantities is obtained by measurements (Fig. 1.16-1.19) or calculations.

Rice. 1.16. “There are 5 minutes left before the train departs,” you measure the time with excitement.

Rice. 1.17 “I bought a kilogram of apples,” says mom about her mass measurements

Rice. 1.18. “Dress warmly, it’s cooler outside today,” your grandmother says after measuring the air temperature outside.

Rice. 1.19. “My blood pressure has risen again,” a woman complains after measuring her blood pressure.

To measure a physical quantity means to compare it with a homogeneous quantity taken as a unit.

Rice. 1.20 If a grandmother and grandson measure distance in steps, they will always get different results

Let's give an example from fiction: “After walking three hundred paces along the river bank, the small detachment entered the arches of a dense forest, along the winding paths of which they had to wander for ten days.” (J. Verne “The Fifteen-Year-Old Captain”)

Rice. 1.21.

The heroes of the novel by J. Verne measured the distance traveled, comparing it with the step, that is, the unit of measurement was the step. There were three hundred such steps. As a result of the measurement, a numerical value (three hundred) of a physical quantity (path) in selected units (steps) was obtained.

Obviously, the choice of such a unit does not allow comparing the measurement results obtained different people, since everyone’s step length is different (Fig. 1.20). Therefore, for the sake of convenience and accuracy, people long ago began to agree to measure the same physical quantity with the same units. Nowadays, in most countries of the world, the law adopted in 1960 is in force. International system units of measurement, which is called the “System International” (SI) (Fig. 1.21).

In this system, the unit of length is the meter (m), time - the second (s); Volume is measured in cubic meters (m3), and speed is measured in meters per second (m/s). You will learn about other SI units later.

3. Remember multiples and submultiples

From your mathematics course, you know that to shorten the notation of large and small values ​​of different quantities, multiples and submultiples are used.

Multiples are units that are 10, 100, 1000 or more times larger than the base units. Sub-multiple units are units that are 10, 100, 1000 or more times smaller than the main ones.

Prefixes are used to write multiples and submultiples. For example, units of length that are multiples of one meter are a kilometer (1000 m), a decameter (10 m).

Units of length subordinate to one meter are decimeter (0.1 m), centimeter (0.01 m), micrometer (0.000001 m), and so on.

The table shows the most commonly used prefixes.

4. Getting to know the measuring instruments

Scientists measure physical quantities using measuring instruments. The simplest of them - a ruler, a tape measure - are used to measure the distance and linear dimensions of the body. You are also well aware of such measuring instruments as a watch - a device for measuring time, a protractor - a device for measuring angles on a plane, a thermometer - a device for measuring temperature, and some others (Fig. 1.22, p. 20). You still have to get acquainted with many measuring instruments.

Most measuring instruments have a scale that allows for measurement. In addition to the scale, the device indicates the units in which the value measured by this device is expressed*.

Using the scale, you can set the two most important characteristics of the device: measurement limits and division value.

Measurement limits- these are the largest and smallest values ​​of a physical quantity that can be measured by this device.

Nowadays, electronic measuring instruments are widely used, in which the value of the measured quantities is displayed on the screen in the form of numbers. Measurement limits and units are determined from the device passport or are set with a special switch on the device panel.

Rice. 1.22. Measuring instruments

Division price- this is the value of the smallest scale division of the measuring device.

For example, the upper measurement limit of a medical thermometer (Fig. 1.23) is 42 °C, the lower one is 34 °C, and the scale division of this thermometer is 0.1 °C.

We remind you: to determine the price of a scale division of any device, it is necessary to divide the difference of any two values ​​indicated on the scale by the number of divisions between them.

Rice. 1.23. Medical thermometer

• Let's sum it up

A general characteristic of material objects or phenomena, which can acquire individual meaning for each of them, is called a physical quantity.

To measure a physical quantity means to compare it with a homogeneous quantity taken as a unit.

As a result of measurements, we obtain the value of physical quantities.

When talking about the value of a physical quantity, you should indicate its numerical value and unit.

Measuring instruments are used to measure physical quantities.

To reduce the recording of numerical values ​​of large and small physical quantities, multiple and submultiple units are used. They are formed using prefixes.

• Security questions

1. Define a physical quantity. How do you understand it?
2. What does it mean to measure a physical quantity?

3. What is meant by the value of a physical quantity?

4. Name all the physical quantities mentioned in the excerpt from J. Verne’s novel given in the text of the paragraph. What is their numerical value? units of measurement?

5. What prefixes are used to form submultiple units? multiple units?

6. What characteristics of the device can be set using the scale?

7. What is the division price called?

• Exercises

1. Name the physical quantities known to you. Specify the units of these quantities. What instruments are used to measure them?

2. In Fig. Figure 1.22 shows some measuring instruments. Is it possible, using only a drawing, to determine the price of division of the scales of these instruments? Justify your answer.

3. Express the following physical quantities in meters: 145 mm; 1.5 km; 2 km 32 m.

4. Write down the following values ​​of physical quantities using multiples or submultiples: 0.0000075 m - diameter of red blood cells; 5,900,000,000,000 m - the radius of the orbit of the planet Pluto; 6,400,000 m is the radius of planet Earth.

5 Determine the measurement limits and the price of division of the scales of the instruments that you have at home.

6. Remember the definition of a physical quantity and prove that length is a physical quantity.

• Physics and technology in Ukraine
  

One of the outstanding physicists of our time - Lev Davidovich Landau (1908-1968) - demonstrated his abilities while still studying at high school. After graduating from university, he interned with one of the creators quantum physics Niels Bohr. Already at the age of 25, he headed the theoretical department of the Ukrainian Institute of Physics and Technology and the department of theoretical physics at Kharkov University. Like most outstanding theoretical physicists, Landau had an extraordinary breadth of scientific interests. Nuclear physics, plasma physics, the theory of superfluidity of liquid helium, the theory of superconductivity - Landau made significant contributions to all these areas of physics. For work in physics low temperatures he was awarded the Nobel Prize.

Physics. 7th grade: Textbook / F. Ya. Bozhinova, N. M. Kiryukhin, E. A. Kiryukhina. - X.: Publishing house "Ranok", 2007. - 192 p.: ill.

Lesson content lesson notes and supporting frame lesson presentation interactive technologies accelerator teaching methods Practice tests, testing online tasks and exercises homework workshops and trainings questions for class discussions Illustrations video and audio materials photographs, pictures, graphs, tables, diagrams, comics, parables, sayings, crosswords, anecdotes, jokes, quotes Add-ons abstracts cheat sheets tips for the curious articles (MAN) literature basic and additional dictionary of terms Improving textbooks and lessons correcting errors in the textbook, replacing outdated knowledge with new ones Only for teachers calendar plans training programs methodological recommendations

Vernier calipers are a very popular measuring tool. The design of a caliper is quite simple, so almost anyone can use it without any special prior preparation. It can be used to measure both external and internal dimensions various parts, as well as the depth of the holes in them. Despite simple design, this instrument has different accuracy classes and can give readings with an accuracy of 0.1 to 0.01 mm. It received its name based on the main design detail. Thanks to its design, the caliper is rightfully considered one of the most versatile measuring instruments.

Using a caliper, you can measure both the external and internal dimensions of various parts, as well as the depth of the holes in them.

Fundamental design characteristics of a caliper

A vernier tool, in principle, and a caliper in this case, has as its main part a retractable rod with measuring scale. This scale is divided into 1 mm divisions, and its total length for the simplest household model ШЦ-1 ranges from 15 to 25 cm. There are also larger models, but they are used only on industrial enterprises and are much less common. It is this rod that determines the maximum value that this particular model of caliper can measure.

Digital caliper The SCC has a digital display mounted on a movable frame.

Special design feature it is the presence of such a device as a vernier. This auxiliary scale, which is movable relative to the main line. It helps to correctly determine the number of division shares on this ruler. The divisions on the vernier scale, also known as “vernier”, are a certain fraction smaller than the divisions of the main ruler. There can be 10 of them for a model with an accuracy of up to 0.1 mm, or 20 for models with an accuracy of up to 0.05 mm. The principle of operation of a vernier is based on the fact that it is much easier to determine by eye the coincidence of divisions than the relative location of one division between two others.

If it is necessary to measure external surfaces, such as the cross-section of a wire, large jaws are simply placed on both sides of the internal surfaces. The wire is clamped between them, and the zero division of the scale of the moving frame gives an indication on the main scale of the rod. Small jaws are shaped like scissor blades, which helps measure the diameter of a pipe or other hole on a scale without additional calculations. They have external working surfaces, having the profile of a sharpened blade, so they can measure such an indicator as the thread pitch.

Components and Applications

The tool consists of a fixed base and retractable fittings. They are made of tool steel. The caliper includes the following components:

1. The main rod on which all movable fittings are attached. The main scale is located on it.
2. A movable frame with a screw lock and pressed by an internal spring plate. There is a vernier scale on it. It can be applied directly to it, or it can be on a plate secured with screws. This allows you to adjust it relative to the scale on the bar.
3. Sponges for measuring external surfaces, or large sponges. One of them is mounted on a fixed rod, and the other on a movable frame. The ends have narrow surfaces, which gives additional features for measurement.
4. Sponges for measuring internal surfaces, or small sponges. They are located according to the same principle opposite the previous ones along the central axis.
5. Ruler for measuring depths. Attached to a movable frame.

The ruler for measuring depth is mounted on a movable frame and moves along a groove made in the plane of the rod. It can also be used to measure internal grooves and shoulder distances. The rod is placed on its end perpendicular to the object being measured. The ruler extends until it rests on the bottom. To measure conical holes, its end has a slight point. After receiving the measurement result, it is recommended to fix the position of the instrument with a locking screw, and only then take readings.

Types of caliper designs and their markings

Along with the simplest mechanical model, the structure of which is discussed above, there are others. They can be divided into 4 main types, having 8 standard sizes. Their designs, as well as their purpose, have some differences. In addition to the double-sided caliper ShTs-1 discussed above, there is a one-sided version ShTsT-1. It has jaws on only one side and a ruler for measuring depths. Although it has a mechanical device, like ShTs-1, the material for its manufacture is hard, high-alloy steel. Such a tool helps to determine the external linear dimensions and depth of holes during abrasive action on the object being measured.

The instrument, called ShTs-2, is equipped with a double-sided design, but the jaws for measuring internal and external surfaces are combined, and have, respectively, flat surfaces on the inside and cylindrical surfaces on the outside. Opposite them are jaws of the same size for measuring external dimensions, which have sharpened edges. This allows you to not only measure, but also mark on the surface of the part being measured. In addition, this model has an auxiliary micrometer feed frame, which allows you to take readings with great accuracy.

The ShTs-3 caliper differs from the previous model only in its one-sided design. Its pair of jaws are designed to measure both internal and external dimensions. This model is designed to measure the largest sizes, so it is also quite large. And what larger sizes measuring device, the greater the resulting measurement error. Therefore, in addition to the designs described above, calipers are divided according to the indicators with which readings are taken.

According to this principle, they are divided into vernier ones, in which the readings are calculated independently based on the movement of the frame, into dial and digital ones. Dials marked ShTsK use the same mechanical principle. On the frame there is a digital scale connected to the bar gear transmission. Whole millimeters are read by the position of the edge of the frame, and their fractions are narrower by the dial. Such a caliper has a higher accuracy class than a vernier caliper and can be up to 0.01 mm. However, it is very vulnerable to mechanical damage and contamination of the rack from the parts being measured.

The use of calipers is inextricably linked with turning production, installation of various pipeline systems, screw connections and other structures that require increased accuracy.

At the same time, thanks to the design, almost everyone can use it. The ShTsTs digital caliper has a digital display mounted on a movable frame. A reading device is built into the frame, indicating the distance between the measuring jaws. There are buttons on the display that allow you to control them. The accuracy of such a device is 0.01 mm and allows you to measure the most small parts, in particular to control the thread. However, all the disadvantages of electronic devices are inherent in this instrument. Changes in rod parameters due to temperature changes immediately affect the display readings.

3. Frontal survey

- Guys, what concepts did we get acquainted with in the last lesson?
– At home, it was necessary to draw a table in a notebook in which it was necessary to distribute the following words into columns (physical body, matter, phenomenon): lead, thunder, rails, blizzard, aluminum, dawn, blizzard, Moon, alcohol, scissors, mercury, snowfall, table, copper, helicopter, oil, boiling, blizzard, shot, flood.

Completion of the table is checked orally.

Meanwhile, one student draws up the solution to the task of converting units of measurement on the board.
Afterwards, the children themselves evaluate the correctness of the completed task.
The most active students who commented and answered confidently, correctly and reasonably should be evaluated.
– The third task was creative: to pick up riddles about physical bodies, phenomena, substances.
- Let's play the game "Chain". The condition of the game is as follows: I will tell you a riddle, and you must not only guess it, but also determine: body, substance or phenomenon. Whoever guesses the answer reads out theirs. Whoever guesses a classmate's riddle offers his own, etc. along the chain. And the last condition: the riddles are not repeated.

Mystery:

Miracle - bird, scarlet tail
Flew into a flock of stars.

- Well done!
Evaluating homework results.
Marks are placed in the journal.
Registration is welcome creative assignment in the form of puzzles, crosswords, drawings.

4. Learning new material

- Guys, how long do you think it took us to check our homework?
-Have you ever had to everyday life Should I still take measurements? Which?
– All of these listed examples are physical quantities. Today in the lesson we will get to know them in more detail and learn how to measure them.( Slide 1).
– Write down the date and topic of the lesson in your notebook: “Measurement is the basis of technology.”
– What measuring instruments are you familiar with? What quantities can be measured with them? ( Slide 2)

– You know a lot of physical instruments!
– Do you know how to determine quantities with their help?
- Shall we check?
– I will divide you into groups of 5 people. And each group will experimentally test and confirm their knowledge.
I divide the class into 5 groups with an equal number of children, but different skills and abilities. Since the groups are of different levels, therefore, it is necessary to select differentiated tasks: low, medium, high level. (Appendix 3 )
When performing the experiment, I remind you of the basic safety rules: working with thermometers, small objects and sharp objects.
The performing student (from each group) is evaluated, and the correctness of homework is also taken into account.
- Well done!
– You have all now proven that you know how to use measuring instruments.
– Tell me, why do we need to know the length and width of the palm?
– Why do we need to know how to determine body weight?

– Where and when did you take your temperature?

– When else can we measure the volume of a body using a ruler?

- Guys, think about how you can determine the volume of air in a classroom?

– Let’s write this formula in a notebook.
– How to determine the volume of a piece of chalk? (Show me the chalk).
– But we are surrounded not only by bodies with the correct geometric shape. For example, a porcelain roller, a Kinder-surprise toy, a spoon, etc.
All items are on display.

– How to determine the volume of an irregularly shaped body? For example, “Kinder-surprise” toys?

– We measure the volume of a small toy with a physical device – a beaker.
– Write down the name of this device in your notebook.
– How to measure body volume with a beaker? To do this, pour a certain amount of water into a beaker. Immerse the entire body being examined into a beaker of water and notice that the water level has increased. The difference in the readings of water volumes will be the desired value - the volume of the body.
– Write the formula in your notebook:
V = V 1 – V 2, where V 1 is the volume of water in the beaker, and V 2 is the volume of water and the body immersed in it.
– Who will determine the volume of a copper cylinder using a beaker?
The following must be taken into account: this experiment is visible only from a seated audience. Therefore, it is demonstrated slide 3(result of the experiment).
– Guys, what do all measuring instruments have in common? ( Slide 2. Hyperlink).
Next, follow the hyperlink to slide 4. The scale and its characteristics.
– Let’s consider a device with the same purpose, but with different scales. On page 9 of the textbook, fig. 11 and 12.
- Guys, tell me if the thermometer readings are the same.
– Which thermometer shows the highest temperature?
– In order to be able to accurately take readings from an instrument, you need to know its division value.
– Write down the subtitle “Division Price” in your notebook.
– The division price is smallest value physical quantity that a device can measure.
– In order to correctly determine the division price, there is a rule. ( Slide 5) We find the same rule in the textbook.
Let's learn to determine the price of a beaker scale division. ( Slide 6).
– Write down the formula for determining the division price:
C = (a – b) / d. ( Slide 7).
We learn to determine the value of scale divisions and measure instrument readings. ( Slides 8, 9).

5. Consolidation of the studied material

- Well done!
- Guys, what new did you learn in class today?

Evaluating those children who were active in the lesson, taking into account group work.

6. Homework

- Let's write it down homework in the diaries. ( Slide 10).
I distribute cards with tasks of two options. ( Appendix 4 )
I answer children’s questions if they arise while getting acquainted with the tasks.
At the next lesson, students check this work with each other and mark it in the margins with a pencil.
– In the remaining time we will play “Understand Me.” ( Slide 11)
– Condition of the game: I ask leading statements, and your task is to guess what is being said as early as possible. If the answer is correct, the answer will appear on the screen.
– What physical quantity can be measured with their help?
– Where else is this device used?

- Second riddle. ( Slide 12).
– Where and for what is this device used?

– Third riddle: ( Slide 13).
– Have you seen this device and where?

The most savvy one also needs to be assessed.

- Well done, thank you all for your attention. Thank you all very much. ( Slide 14).

Every person who works in a certain field of activity encounters measuring instruments. With their help, you can measure certain indicators and measure various objects.

You can buy such devices here, where they are available in huge assortment. The accuracy of the result you get in the end depends on the quality of the measuring device.

Determining the value of the scale division

A certain value, called the scale division price, is calculated according to certain rules.

Here are the main points to remember:

• at the very beginning you need to take those scale values ​​that are located nearby;
• then you need to calculate their difference;
• after this, count the number of intermediate divisions that are located between the same values;
• at the very end, the resulting difference is divided by the number of intermediate divisions.

These are the main steps that will allow you to determine the price of the scale division. If you did it right, you can get the maximum exact result.

Such devices have advantages that set them apart from other options. Measuring instruments are stable and can last as long as possible long term, show the result with the highest accuracy.

Specialists who work in different areas activities, often use multifunctional devices. Using such equipment, you can measure different indicators simultaneously.

Modern measuring devices allow you to store data in memory and sort it into archives. If you need to return to past information in the future, you will retrieve it and review it carefully.

Measuring instruments have other advantages. For example, one device replaces several models at once.

It will be convenient for you to use such equipment, because it is very easy to move it from place to place. You will have hands free, so you won't drop or break anything.

Main types of measuring equipment

You can use a rangefinder to measure different distances. This is a laser tool that accurately determines the depth of the well and the length of the load-bearing wall.

To get the most accurate result from leveling, you need to purchase an optical level. This device can solve many tasks and problems.

You can draw lines, apply markings or project different planes using a laser plane builder. Such a tool is indispensable during repairs or complex construction work.

Physical quantities. Measurement of physical quantities. We look at the accuracy and error of measurements in the video:

Meter solar radiation(lux meter)

To help technical and scientific workers, many measuring instruments have been developed to ensure accuracy, convenience and efficiency of work. At the same time, for most people the names of these devices, and even more so the principle of their operation, are often unfamiliar. In this article we will briefly explain the purpose of the most common measuring instruments. The website of one of the measuring instrument suppliers shared information and images of the instruments with us.

Spectrum Analyzer- This meter, which serves to observe and measure the relative energy distribution of electrical (electromagnetic) oscillations in a frequency band.

Anemometer– a device designed to measure the speed and volume of air flow in a room. An anemometer is used for sanitary and hygienic analysis of territories.

Balometer– measuring device for direct measurement volumetric flow air on large supply and exhaust ventilation grilles.

Voltmeter- This is a device that measures voltage.

Gas analyzer- a measuring device for determining the qualitative and quantitative composition of gas mixtures. Gas analyzers can be manual or automatic. Examples of gas analyzers: freon leak detector, hydrocarbon fuel leak detector, soot number analyzer, flue gas analyzer, oxygen meter, hydrogen meter.

Hygrometer is a measuring device that is used to measure and control air humidity.

Rangefinder- a device that measures distance. The rangefinder also allows you to calculate the area and volume of an object.

Dosimeter– a device designed to detect and measure radioactive radiation.

RLC meter– radio measuring instrument used to determine admittance electrical circuit and impedance parameters. RLC in the name is an abbreviation of the circuit names of the elements whose parameters can be measured by this device: R - Resistance, C - Capacitance, L - Inductance.

Power meter– a device that is used to measure the power of electromagnetic oscillations of generators, amplifiers, radio transmitters and other devices operating in the high-frequency, microwave and optical ranges. Types of meters: absorbed power meters and transmitted power meters.

Harmonic distortion meter– a device designed to measure the coefficient of nonlinear distortion (harmonic distortion) of signals in radio devices.

Calibrator– a special standard measure that is used for verification, calibration or calibration of measuring instruments.

Ohmmeter or resistance meter is a device used to measure resistance electric current in ohms. Types of ohmmeters depending on sensitivity: megohmmeters, gigaohmmeters, teraohmmeters, milliohmmeters, microohmmeters.

Current clamps- an instrument that is designed to measure the amount of current flowing in a conductor. Current clamps allow you to take measurements without breaking the electrical circuit and without disrupting its operation.

Thickness gauge is a device with which you can measure its thickness on a surface with high accuracy and without compromising the integrity of the coating. metal surface(for example, a layer of paint or varnish, a layer of rust, primer, or any other non-metallic coating applied to a metal surface).

Luxmeter is a device for measuring the degree of illumination in the visible region of the spectrum. Light meters are digital, highly sensitive instruments such as lux meter, brightness meter, pulse meter, UV radiometer.

Pressure gauge– a device that measures the pressure of liquids and gases. Types of pressure gauges: general technical, corrosion-resistant, pressure gauges, electrical contact.

Multimeter is a portable voltmeter that performs several functions simultaneously. The multimeter is designed to measure DC and AC voltage, current, resistance, frequency, temperature, and also allows for continuity testing and diode testing.

Oscilloscope is a measuring device that allows you to observe and record, measure the amplitude and time parameters of an electrical signal. Types of oscilloscopes: analog and digital, portable and desktop

Pyrometer- this is a device for non-contact measurement object temperature. The principle of operation of the pyrometer is based on measuring the power of thermal radiation of the measured object in the range of infrared radiation and visible light. The accuracy of temperature measurement at a distance depends on the optical resolution.

Tachometer is a device that allows you to measure the rotation speed and number of revolutions of rotating mechanisms. Types of tachometers: contact and non-contact.

Thermal imager is a device designed to observe heated objects by their own thermal radiation. The thermal imager allows you to convert infrared radiation into electrical signals, which are then, in turn, after amplification and automatic processing, converted into a visible image of objects.

Thermohygrometer is a measuring device that simultaneously performs the functions of measuring temperature and humidity.

Line defect detector is a universal measuring device that allows you to determine the location and direction on the ground cable lines and metal pipelines, as well as determine the location and nature of their damage.

pH meter is a measuring device designed to measure the hydrogen index (pH indicator).

Frequency meter– a measuring device for determining the frequency of a periodic process or the frequencies of the harmonic components of the signal spectrum.

Sound level meter– a device for measuring sound vibrations.

Table: Units of measurement and designations of some physical quantities.

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