What is the principle of the scale and the structural characteristics of the scale

Using the principle of lever balancing, the gravity of the water in a keg is balanced with the gravity of a small lump. At this time, the point of gravity of the small stone on the metal rod is the position of the density of water on the rod. Drain the water from the bucket and fill it with the liquid to be tested.

But its volume must be equal to the volume of water. The gravity of the liquid to be measured is again balanced with the gravity of the small stone. The position of the small stone on the lever is about to change.

Due to the different densities of the same volume of liquid. Therefore, the change in the position of the small stone is entirely due to the change in the density of the liquid. Therefore, the position of the gravity of the small stone on the rod is actually the density value of the liquid to be measured.

For example, if it is alcohol, the alcohol density is less than that of water. Therefore, the arm of a small stone is smaller than that of water.

That is, the punctuation of the alcohol density, on the right side of the water. In the case of sulfuric acid, it is denser than water. The arm of a small stone should be larger than that of water.

That is, the punctuation of the sulfuric acid density is on the left side of the water. Therefore, if the density is less than water, the punctuation of its density is to the right of the punctuation point of water; Any liquid that is denser than water must have the punctuation of its density. Fill the liquid to be measured.

In the case of sulfuric acid, the position of the gravity of the small stone on the pole. That is, the punctuation of the alcohol density. So, the gravity of the water is balanced by the gravity of the small blocks.

So whatever is less dense than water: if it is alcohol, the alcohol is less dense than water. Due to the different densities of the same volume of liquid.

So. That is, the punctuation of the sulfuric acid density is on the left side of the water, on the right side of the water. The arm of a small stone should be larger than that of water.

At this time; Any liquid that is denser than water. The position of the small stone on the lever will change, and the punctuation of its density must be to the left of the punctuation of the water. So.

For example, the point of gravity of a small stone on a metal rod is the position of the density of water on the rod, and the punctuation of its density is on the right side of the punctuation point of water. The gravity of the liquid to be measured is again balanced with the gravity of the small stone. Pour out the water in the bucket, the arm of the small stone is smaller than the water, and the position of the small stone changes.

But its volume must be equal to the volume of water, and its density is greater than that of water, which is entirely due to the change in the density of the liquid, which is actually the density value of the liquid to be measured using the principle of lever equilibrium, in a small keg.

Scale: A tool for measuring the length of an object.

The position of the zero tick mark, the index value, the range.

There are three basic elements of a scale: range, graduation value, and zero scale mark. First of all, see whether the zero scale mark of the scale is worn; secondly, look at the measurement range (i.e., range) of the scale; Finally, look at the minimum graduation value of the scale.

When using, select the appropriate scale according to the range of the scale to measure quietly, the scale is aligned with the measured object, and the next digit of the graduation value is estimated to be read.

Notes:

Recognize the scale of the scale (i.e., the measurement range), the index value (i.e., the value represented by the smallest scale), and the zero scale mark (the scale with zero scale wear can be measured from a whole scale line that can be seen clearly).

The zero tick mark or a certain numerical tick mark is aligned with the beginning of the object to be measured, so that the edge of the scale ruler is close to the object to be measured, parallel to the measured length, and cannot be tilted.

The line of sight is perpendicular to or directly opposite the scale face.

Readings are taken to the next digit of the graduation value (in junior high school physics, the measurement of length is the only thing that must be estimated). For example, the graduation value of the scale in the figure below is 1mm, then the reading should be estimated below the millimeter, and the estimated reading will vary with the different measurers, which is the error generated in the length measurement, which is inevitable.

The scale is a tool for measuring the length of an object, and the graduation value of the scale is generally 1mmMeasuring length with a scale is a fundamental skill in physical experiments, and it is also the basis for correct readings from other measuring instruments.

1) Use the scale correctly for shed culture.

Before use: do three looks, that is, first see whether the zero scale of the scale is worn, if it has been worn, you should re-select a scale value as the starting point of measurement.

secondly, look at the measurement range (i.e., range) of the scale; In principle, the length measurement requires a measurement, if the measurement range is less than the actual length, it is necessary to move the scale to measure several times, which will produce a large error.

Finally, look at the minimum scale value of the scale. The length value represented by the smallest scale not only reflects the different accuracy of the scale, but also relates to the validity of the measurement results. The range and minimum scale value should be selected based on the actual measurement requirements.

When using: Attention should be paid to proper placement and proper observation when using.

The key to correct placement is to do this: the ruler edge is aligned with the measured object, and it must be placed in a positive and overlapping position, and cannot be skewed; The facets of the ruler must be close to the object to be measured and cannot be "suspended".

The key to correct observation is to look directly in front of the terminal tick mark, and the line of sight is perpendicular to the potato noodles in the engraving, and the number of large and small grids can be seen clearly.

2) Record the measurement results correctly.

In general, it is estimated to read the next digit of the minimum tick value. If the minimum scale of the triangular ruler is mm, and the length of 2cm is measured with it, if it is exactly aligned on the scale line, the correct record should be, where is the number accurately read by the ruler, and since there is no estimated reading, it is necessary to add "0" to the 10th decile of the millimeter

Note: The corresponding units must be written when recording the measurement results.

3) Conversion of length units.

You should master the conversion between the six units of km, m, dm, cm, mm, and m. where km m mm m each level is a kilocidal; Each level of m dm cm mm is a decimal place. The correct way to write the conversion should be:

Convert the digit by the unit after the carry scale. Example:

4) Correctly recognize errors.

The reason for the error comes from the accuracy of the measuring instrument, the limitations of the experimental principle, the objective factors of the environment and man-made, etc. Therefore, errors in any measurement are inevitable. We can only try to reduce the small error of the chain sail, and it is impossible to eliminate the error.

Errors are different from errors in that they are caused by improper methods and subjective factors (misreading, misremembering, etc.), so mistakes should be avoided and can be avoided in experiments.

Ways to reduce errors: select measuring instruments with high accuracy, improve experimental methods, and be proficient in experimental skills. In general experiments, the effective way to reduce the error is to take the average of multiple measurements (this method is effective for the reduction of accidental error).

Ruler. A ruler, also known as a measuring ruler and a scale ruler, is a tool used to draw line segments (especially straight ones) and measure length. There is usually a scale on the ruler to measure the length.

Some rulers, with a special shape such as a letter or a circular hole in the middle, are convenient for users to draw, and are usually used to measure the length, which are generally divided into tape measures, vernier calipers, rectangular rulers, and rulers.

The ruler used in different occasions has different requirements and standards, and if the value is more accurate, then it requires a high level of technology and must be produced with the help of machines.

In addition to the accuracy of the ruler, the second focus is the quality of the engraved value, which will generally be branded with a protective film after the engraved value, and the third point is the selection of materials, which is now divided into plastic, metal, and wooden rulers, plastic rulers are mainly used by general students to use stationery, metal rulers are more used in industry, and wooden rulers are mainly used for teaching.