Laboratory work in physics. Visual physics

Visual physics provides the teacher with the opportunity to find the most interesting and effective methods learning, making classes interesting and more intense.

The main advantage of visual physics is the ability to demonstrate physical phenomena from a wider perspective and comprehensively study them. Each work covers a large volume educational material, including from different branches of physics. This provides ample opportunities for consolidating interdisciplinary connections, for generalizing and systematizing theoretical knowledge.

Interactive work in physics should be carried out in lessons in the form of a workshop when explaining new material or when completing the study of a certain topic. Another option is to perform work outside of school hours, in elective, individual classes.

Virtual physics(or physics online) is a new unique direction in the education system. It's no secret that 90% of information enters our brain through the optic nerve. And it is not surprising that until a person sees for himself, he will not be able to clearly understand the nature of certain physical phenomena. Therefore, the learning process must be supported by visual materials. And it’s simply wonderful when you can not only see a static picture depicting any physical phenomenon, but also look at this phenomenon in motion. This resource allows teachers, in an easy and relaxed manner, to clearly demonstrate not only the operation of the basic laws of physics, but will also help conduct online laboratory work in physics in most sections in general educational program. For example, how can one explain in words the principle p-n actions transition? Only by showing an animation of this process to a child does everything immediately become clear to him. Or you can clearly show the process of electron transfer when glass rubs on silk, and after that the child will have fewer questions about the nature of this phenomenon. In addition, visual aids cover almost all sections of physics. So for example, want to explain the mechanics? Please, here are animations showing Newton's second law, the law of conservation of momentum when bodies collide, the motion of bodies in a circle under the influence of gravity and elasticity, etc. If you want to study the optics section, nothing could be easier! Experiments on measuring the wavelength of light using a diffraction grating, observation of continuous and line emission spectra, observation of interference and diffraction of light, and many other experiments are clearly shown. What about electricity? And this section is given quite a few visual aids, for example there is experiments to study Ohm's law for complete circuit, mixed conductor connection research, electromagnetic induction, etc.

Thus, the learning process from the “obligatory task” to which we are all accustomed will turn into a game. It will be interesting and fun for the child to look at animations of physical phenomena, and this will not only simplify, but also speed up the learning process. Among other things, it may be possible to give the child even more information than he could receive in the usual form of education. In addition, many animations can completely replace certain laboratory instruments, thus it is ideal for many rural schools, where, unfortunately, it is not always possible to find even a Brown electrometer. What can I say, many devices are not even in regular schools large cities. Perhaps by introducing such visual aids into the compulsory education program, after graduating from school we will get people interested in physics, who will eventually become young scientists, some of whom will be able to make great discoveries! Thus, the scientific era of great domestic scientists will be revived and our country will again, as in Soviet times, create unique technologies ahead of their time. Therefore, I think it is necessary to popularize such resources as much as possible, to inform about them not only to teachers, but also to schoolchildren themselves, because many of them will be interested in studying physical phenomena not only in lessons at school, but also at home free time and this site gives them such an opportunity! Physics online it's interesting, educational, visual and easily accessible!

(All works on mechanics)

Mechanics

No. 1. Physical measurements and calculation of their errors

Introduction to some methods physical measurements and calculation of measurement errors using the example of determining the density of a solid body of regular shape.

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No. 2. Determination of the moment of inertia, moment of force and angular acceleration of the Oberbeck pendulum

Determine the moment of inertia of the flywheel (cross with weights); determine the dependence of the moment of inertia on the distribution of masses relative to the axis of rotation; determine the moment of force that causes the flywheel to rotate; determine the corresponding values ​​of angular accelerations.

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No. 3. Determination of the moments of inertia of bodies using a trifilar suspension and verification of Steiner's theorem

Determination of the moments of inertia of some bodies by the method of torsional vibrations using a trifilar suspension; verification of Steiner's theorem.

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No. 5. Determining the speed of a “bullet” by the ballistic method using a unifilar suspension

Determination of the flight speed of a “bullet” using a torsional ballistic pendulum and the phenomenon of absolutely inelastic impact based on the law of conservation of angular momentum

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No. 6. Study of the laws of motion of a universal pendulum

Determination of gravitational acceleration, reduced length, position of the center of gravity and moments of inertia of a universal pendulum.

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No. 9. Maxwell's pendulum. Determination of the moment of inertia of bodies and verification of the law of conservation of energy

Check the law of conservation of energy in mechanics; determine the moment of inertia of the pendulum.

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No. 11. Study of rectilinear uniformly accelerated motion phone on Atwood's car

Determination of free fall acceleration. Determination of the moment of the “effective” resistance force for the movement of loads

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No. 12. Study of the rotational motion of the Oberbeck pendulum

Experimental verification of the basic equation for the dynamics of rotational motion of a rigid body around a fixed axis. Determination of the moments of inertia of the Oberbeck pendulum at various positions of the loads. Determination of the moment of the “effective” resistance force for the movement of loads.

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Electricity

No. 1. Study of the electrostatic field using modeling method

Constructing a picture of the electrostatic fields of flat and cylindrical capacitors using equipotential surfaces and field lines; comparison of experimental voltage values ​​between one of the capacitor plates and equipotential surfaces with its theoretical values.

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No. 3. Study of the generalized Ohm's law and measurement of electromotive force by the compensation method

Studying the dependence of the potential difference in the section of the circuit containing the EMF on the current strength; calculation of the EMF and impedance of this section.

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Magnetism

No. 2. Checking Ohm's law for AC

Determine the ohmic and inductive resistance of the coil and the capacitive resistance of the capacitor; check Ohm's law for alternating current with different circuit elements

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Oscillations and waves

Optics

No. 3. Determining the wavelength of light using a diffraction grating

Familiarization with a transparent diffraction grating, determining the wavelengths of the spectrum of a light source (incandescent lamp).

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Quantum physics

No. 1. Testing black body laws

Study of dependencies: spectral density of energy luminosity of an absolutely black body on the temperature inside the furnace; voltage on the thermocouple from the temperature inside the furnace using a thermocouple.

​ How to complete and submit laboratory work

When studying physics, students must learn how to perform and correctly format laboratory work. The main thing in the first physics lessons is to teach students to become familiar with the basic techniques for conducting physical measurements and the rules for processing the results. At the same time, certain skills must be developed, which is a prerequisite for further successful work in physics lessons. The purpose of laboratory work is to enhance students' understanding of physical phenomena and laws. This task can be successfully solved only if laboratory work is carried out with a sufficient understanding of the essence of the phenomena being studied. Therefore, home preparation for laboratory work is one of the most important stages.

Preparation for laboratory work.

When preparing for work, it is recommended to adhere to the following plan.

Read the description of the work from beginning to end, without lingering on the derivation of formulas. The task of the first reading is to find out what the purpose of the laboratory work is, what physical law or phenomenon is being studied in this work and by what method it is carried out.

Read the material related to this work from the textbook. Analyze the derivation of the formula using the textbook (if necessary). Find answers to test questions, given at the end of the job description (if available).

Consider in the textbook the structure and operating principle of the devices that will be used in the work.

Find out which physical quantities and with what accuracy will be directly measured and what their names are.

In the description of the laboratory work in the textbook, consider the basic diagram of the experiment and the table in which the measurement results will be entered. If there is no table in your work, create one.

Think about what final result and conclusion should be obtained in this laboratory work.

Performing laboratory work.

When performing work, you should first familiarize yourself with the devices. It is necessary to establish their compliance with the description, and perform the sequence of actions recommended in the device description to prepare the device for operation. Determine the scale division value of the instrument and its measurement error. Next, a preliminary experiment should be carried out in order to observe qualitatively the phenomenon being studied and to assess the limits within which the measured values ​​lie. After the preparation has been completed, you can begin measurements. It should be remembered that each measurement, if possible, should be performed more than once.

Measurements made using instruments are recorded immediately after they are performed in the form as they are read from the instrument scale - without any conversion to the scale multiplier (if any) or system of units. The units of measurement (multiplier) must be written in the header of the corresponding table or in the column with the measurement results. All notes when performing laboratory work must be kept exclusively in a notebook for laboratory work (it is also possible on a draft or a specially prepared form (protocol) for draft notes. This form is a draft, and the notebook is a clean copy. It should be kept in the most careful manner. In a notebook for laboratory work, the completed work is documented in accordance with the instructions for its implementation.

Design of laboratory work.

Illegitimately prepared working records of the procedure for performing laboratory work and measurement results can negate all the work done.

It is not difficult to learn how to correctly write out laboratory work in a notebook; you just need to carefully follow some basic requirements. Recording the results when performing laboratory work can be done both in a notebook and on separate signed sheets.

When performing laboratory work, it is very important to immediately write down everything done.All results of direct measurements should be written down immediately and without any processing only with a pen. There are no exceptions to this rule. Records should be such that they can be understood without much difficulty after some time. Examples of common errors are ambiguity and ambiguity. Letters and numbers must be written clearly.

The habit of correcting numbers is the enemy of clarity. Don’t force your teacher, who is checking your notes in your notebook, and yourself, to rack your brains over the corrected numbers.

Do not carry out any, even the simplest calculations in your head, before writing down the measurement result.

Don't forget to make a drawing or installation diagram in your notebook when necessary. There is an ancient Chinese proverb: “A picture is worth a thousand words.” The drawing and its inscriptions must be done in pencil so that you can use an eraser to correct mistakes.

If it is possible to carry out preliminary calculations without errors, then this must be done to ensure that the experiment was performed correctly. If it is possible to create a graph in your work, this must be done. On graphs, the cause is usually plotted horizontally, and the effect vertically.

So, correctly formatted should contain the following sections.

Title of the work and its no.

Equipment.

Data for calculating measurement error.

The purpose of the work (you don’t have to write it down. It is formulated in the textbook).

A drawing or diagram of the installation with the symbols of the measured quantities used in the work (if necessary).

The order of work.

Results of all direct measurements.

a) records of measurement results should not allow different interpretations;

b) crossed out entries that appear to be erroneous so that they can be read if necessary;

c) do not allow erasures and scribbles of notes, do not allow rewriting of the work. This leads to possible loss of information and eliminates the possibility of falsifying results.

Results of measurements and calculations (without errors) in the form of tables.

Charts.

Conclusion (must correspond to the purpose of the work). In the conclusion, indicate the measurement error.

Criteria for evaluating laboratory work.

Rating "5" is given if the student completes the work in full in compliance with the necessary sequence of experiments and measurements, independently and rationally assembles necessary equipment, conducts all experiments under conditions and modes that ensure the receipt of correct results and conclusions, complies with the requirements of safety regulations, correctly and accurately completes all records, tables, drawings, drawings, graphs, and correctly performs error analysis.

Rating "4" is given if all the requirements for a “5” rating are met, but two or three shortcomings were made, no more than one minor error and one shortcoming

Rating "3" is given if the work is not completed completely, but the volume of the completed part allows us to obtain the correct result and conclusion, or if errors were made during the experiment and measurement

Rating "2" is given if the work is not completed completely, or the volume of the completed part of the work does not allow correct conclusions to be drawn, or if experiments, measurements, calculations, observations were carried out incorrectly.

In all cases, the grade is reduced if the student did not follow the safety rules!

Gross errors:

ignorance definitions of basic concepts, laws, rules, basic principles of theory, formulas, generally accepted symbols for designating physical quantities, units of their measurement;

inability highlight the main thing in the answer;

inability apply knowledge to solve problems and explain physical phenomena, incorrectly formulated questions of a problem or incorrect explanations of the progress of its solution, ignorance of techniques for solving problems similar to those previously solved in class, errors showing an incorrect understanding of the conditions of the problem or incorrect interpretation of the solution;

inability read and construct graphs and circuit diagrams;

inability prepare installation or laboratory equipment for operation, conduct experiments, necessary calculations, or use the data obtained to draw conclusions;

careless attitude towards laboratory equipment and measuring instruments;

inability determine the reading measuring instrument;

violation requirements of safe labor rules when performing the experiment.

Minor errors:

inaccuracy formulations, definitions, concepts, laws, theories caused by incomplete coverage of the main features of the concept being defined, errors caused by non-compliance with the conditions for conducting experiments or measurements;

errors V symbols on circuit diagrams, inaccuracies in drawings, graphs, diagrams;

pass or inaccurate spelling of the names of units of measurement of physical quantities;

irrational choice of solution.

Measurement errors.

Performing laboratory and practical work in physics is associated with the measurement of various physical quantities and subsequent processing of their results. Measurement is the operation of comparing the size of the object under study with the size of a single object (orMeasurement - finding the value of a physical quantity experimentally using means). So, for example, a meter is taken as a unit of length, and as a result of measuring the length of a certain segment, it is determined how many meters are contained in this segment. In physics and technology there are no absolutely accurate instruments and other means of measurement, therefore, there are no absolutely accurate results measurements. However, you still have to measure. How much can you trust the results obtained?

It is customary to distinguishdirect and indirect measurements . With direct In measurement, a direct comparison of the size of the measured object with the size of a single object is made. In other words, this is a measurement in which the result is directly in the process of being read from the scale (or readings from a digital device). As a result, the desired value is found directly from the readings of the measuring device, for example, volume - from the level of liquid in the measuring cylinder (beaker), weight - from the stretch of the dynamometer spring, etc. Direct measurement error (indicated by∆ ) depends only on the quality of the measuring device. In a physics textbook for the seventh grade by A.V. Peryshkin introduces the concept of measurement error (page 11 of the textbook):the measurement error ∆a is equal to half the division value of the measuring device and that when recording the measured value, taking into account the error, one should use the formula

A = measurement result + ∆a.

In the 10th grade, this concept is formulated differently: the error of direct measurement consists of the instrumental error of the device∆i A and reading errors∆о A . Probably, the author of the 7th grade textbook used the so-called “negligible errors” rule:Both components of the direct measurement error should be taken into account only if they are close to each other. Any of these terms can be neglected if it does not exceed 1/3 - 1/4 of the other.

Instrumental

error

+

Student ruler

Up to 30 cm

1 mm

1 mm

Drawing ruler

Up to 50 cm

1 mm

0.2 mm

Tool ruler (steel)

Up to 30 cm

1 mm

0.1 mm

Demonstration ruler

100 cm

1 cm

0.5 cm

Measuring tape

150 cm

0.5 cm

0.25 cm

Measuring cylinder

Up to 250 ml

1 ml

1 ml

Calipers

150 mm

0.1 mm

0.05 mm

Micrometer

25 mm

0.01 mm

0.005 mm

Training dynamometer

4 N

0.1 N

0.05 N

Mechanical stopwatch

0-30 min

0.2 s

1 s per 30 min

Electronic stopwatch

100 s

0.01 s

0.01 s

Aneroid barometer

720-780 mmHg

1 mmHg

3 mmHg

Alcohol thermometer

0-100 оС

1 оС

1 оС

School ammeter

2 A

0.1 A

0.05 A

School voltmeter

6 V

0.2 V

0,1

Probably, the concept of measurement error should have been introduced differently in 7th grade:The measurement error ∆a is equal to the instrumental error of the measuring device. Since the measurements taken during laboratory work in grade 7 use simple, but still measuring instruments (ruler, measuring tape, measuring cylinder, dynamometer, etc.),

The instrumental error of measuring instruments, for example, for linear dimensions, is usually indicated on the instrument itself in the form of an absolute error or in the form of a division value. If this is not on the device, then it is taken equal to half the price of the smallest division. As a rule, the scale division price of instruments is consistent with the instrumental error. For devices with a digital readout of measured quantities, the method for calculating the error is given in the device's passport data. If this data is missing, then the absolute error is taken to be a value equal to half the last digital digit of the indicator. Reading error∆oA is due to the fact that the instrument pointer does not always exactly coincide with the scale divisions (for example, the arrow on the scale of a dynamometer, voltmeter). In this case, the reading error does not exceed half the scale division value and the reading error is also taken as half the scale division value∆о A = s/2, where s is the scale division value of the measuring device. The reading error must be taken into account only when, during the measurement, the instrument pointer is located between the divisions marked on the instrument scale. It makes no sense at all to talk about, let alone try to take into account the reading errors of digital instruments. Both components of the direct measurement error should be taken into account only if they are close to each other.
In school laboratory practice, methods of mathematical statistics are practically not used in measurement. Therefore, when performing laboratory work, it is necessary to determine the maximum errors in measuring physical quantities.

However, much more often measurements are carried out indirectly, for example, the area of ​​a rectangle is determined by measuring the lengths of its sides, - by measurements of mass and volume, etc. In all these cases, the desired value of the measured quantity is obtained through appropriate calculations.Indirect measurement - determination of the value of a physical quantity using a formula connecting it with other physical quantities determined by direct measurements.

The result of any measurement always contains some error. Therefore, the measurement task includes not only finding the value itself, but also estimating the error allowed during the measurement. If an estimate of the error in the result of a physical measurement is not made, then we can assume that the measured quantity is generally unknown, since the error can, generally speaking, be of the same order as the measured quantity itself or even greater. This is the difference between physical measurements and household or technical ones, in which, as a result, practical experience it is known in advance that the selected measuring instrument provides acceptable accuracy, and the influence of random factors on the measurement result is negligible compared to the division cost of the instrument used.

Errors in physical measurements are usually divided into systematic, random and gross. Systematic errors are caused by factors that act in the same way when the same measurements are repeated many times. Systematic errors are hidden in the inaccuracy of the instrument itself and unaccounted factors when developing the measurement method. Typically, the systematic error of a device is indicated in its technical data sheet. As for the measurement method, everything depends on the qualifications of the experimenter. Although the total systematic error in all measurements carried out in a given experiment will always lead to either an increase or decrease in the correct result, the sign of this error is unknown. Therefore, a correction cannot be made for this error, but this error must be attributed to the final measurement result.

Random errors owe their origin to a number of reasons, the effect of which is not the same in each experiment and cannot be taken into account. They have different meanings even for measurements made in the same way, that is, they are random. Let's say it's donen repeated measurements of the same quantity. If they are performed using the same method, under the same conditions and with the same degree of care, then such measurements are called equally accurate.

The third type of errors that we have to deal with are gross errors or misses. Gross measurement error refers to an error that is significantly greater than expected under given conditions. It can be made due to incorrect use of the device, incorrect recording of device readings, erroneous reading of the reading, failure to take into account the scale multiplier, etc.

Calculation of errors.

Let us introduce the following notations: A, B, .... -physical quantities. Apr -approximate value of a physical quantity , i.e. a value obtained by direct or indirect measurements. Let us recall thatabsolute error approximate number is the difference between this number(Measured) and its exact meaning(True) , and neither the exact value nor the absolute error are fundamentally unknown and must be assessed based on the measurement results.

∆ A = Aism - Stork

Relative error (εа) approximate number (measurement of a physical quantity) is the ratio of the absolute error of the approximate number to this number itself.

εA = ∆A /Aism

Maximum absolute error direct measurements consists of the absolute instrumental error and the absolute reading error in the absence of other errors:
∆A = ∆andA + ∆andA

∆andA -absolute instrumental error , determined by the design of the device (measuring instrument error). Found in tables.
∆iA -absolute reading error (obtained from insufficiently accurate readings of measuring instruments), it is equal in most cases to half the division value; when measuring time - the price of a stopwatch or clock division.

The absolute measurement error is usually rounded to one significant figure (∆A ~ 0.18 = 0.20). The numerical value of the measurement result is rounded so that it last digit turned out to be in the same category as the error figure (A ~ 12.323 = 12.30).

Formulas for calculating relative errors for various cases are given in the table.

How to use this table?

Let, for example, a physical quantityρ calculated by the formula:

ρ = m/V . Valuesm AndV found by direct measurements during laboratory work. Their absolute errors are respectively equal∆m = ∆ Andm + ∆оm And∆V = ∆ AndV + ∆оV . Gj Substituting the obtained values∆m And∆V, m AndV into the formula, we get an approximate value∆ρ = ∆m/∆V. Substituting similarlym AndV into the formula, we get the valueρpr . Next, you should calculate the relative error of the resultερ . This can be done by using the appropriate formula from the fourth row of the table.ερ = εm + εV = ∆m/m + ∆V/V

Since, due to the presence of random errors, measurement results by their nature also represent random variables, true valueρist the measured value cannot be specified. However, it is possible to establish a certain interval of values ​​of the measured quantity near the value obtained as a result of measurementsρ pr , which contains with a certain probabilityρist . ρpr - ∆ρ ≤ ρist ≤ ρpr + ∆ρ.

Then the final result of density measurements can be written in the following form:

ρist = ρpr ± ∆ρ

Task best estimate valuesρist and determining the limits of the interval based on measurement results is the subject of mathematical statistics. But that's a separate conversation...

About numerical calculations

When making calculations, they usually use a microcalculator; as a result, the indicator in the answer automatically produces as many numbers as can fit on it. This creates the impression that the result is overly accurate. At the same time, the measurement results are approximate numbers. Let us recall (see, for example, M.Ya. Vygodsky, Handbook on elementary mathematics), which for approximate numbers distinguishes the entry 2.4 from 2.40, the entry 0.02 from 0.0200, etc. The notation 2.4 means that only the whole and tenth digits are correct, but the true value of the number could be, for example, 2.43 or 2.38. Writing 2.40 means that hundredths are also true; the true number may be 2.403 or 2.398, but not 2.421 or 2.382. The same distinction is made for integers. The entry 382 means that all numbers are correct. If you cannot vouch for the last digit, then the number is rounded, but written not in the form of 380, but in the form of 38·10. Writing 380 means that the last digit (zero) is correct. If only the first two digits of the number 4720 are correct, it must be written as 47·102 or 4.7·103. In cases where the numerical values ​​of physical quantities are much greater or much less than one, they are usually written as a number between 1 and 10, multiplied by the corresponding power of ten.

The number of characters in the final result is determined according to the following rules. First, the number of significant digits of the error is limited. Significant digits are all the correct digits of a number except the zeros in front of the number. For example, the number 0.00385 has three significant digits, the number 0.03085 has four significant digits, the number 2500 has four, and the number 2.5 103 has two. The error is always recorded with one or two significant figures. In doing so, we are guided by the following considerations.

The value of a random error obtained from processing the results of a certain number of measurements is itself a random number, i.e., if we do the same number of measurements again, then, generally speaking, we will obtain not only a different result for the measured value, but also a different estimate for error. Since the error turns out to be a random number, using the laws of mathematical statistics, it is possible to find a confidence interval for it. Corresponding calculations show that even with quite large number measurements, this confidence interval turns out to be very wide, i.e. The magnitude of the error is estimated quite roughly. So, with 10 measurements, the relative error of the error exceeds 30%. Therefore, it should be given two significant figures if the first one is 1 or 2, and one significant figure if it is equal to or greater than 3. This rule is easy to understand if you consider that 30% of 2 is 0.6, and of 4 already 1.2. Thus, if the error is expressed, for example, by a number starting with the number 4, then this number contains an inaccuracy (1.2) exceeding one in the first digit.

Once the error is recorded, the result value must be rounded so that its final significant figure was of the same category as the error. An example of the correct presentation of the final result:t = (18.7± 1.2)·102s.

Rules for constructing graphs

Graphs are drawn on graph paper, on which coordinate axes are first plotted. At the ends of the axes, the physical quantities and their dimensions are indicated. Then scale divisions are applied to the axes so that the distance between the divisions is 1, 2, 5 units (or 0.1, 0.2, 0.5, or 10, 20, 50, etc.). Typically the order of scale, i.e. 10±n is placed at the end of the axis. For example, for the path traveled by the body, instead of 1000, 1100, 1200, etc. meters near the scale divisions they write 1.0, 1.1, 1.2, and at the end of the axis physical quantity denoted as S, 103 m or S·10-3, m. The intersection point of the axes does not necessarily have to correspond to zero along each of the axes. The origin of the axes and scales should be chosen so that the graph occupies the entire coordinate plane. After constructing the axes, experimental points are plotted on graph paper. They are designated by small circles, squares, etc. If several graphs are constructed on one coordinate plane, then different designations are chosen for the points. Then, from each point up, down and to the right, to the left, segments are plotted corresponding to the errors of the points on the scale of the axes. If the error on one of the axes (or on both axes) turns out to be too small, then it is assumed that it is displayed on the graph by the size of the point itself.

Experimental points, as a rule, are not connected to each other either by straight segments or by an arbitrary curve. Instead, a theoretical graph of the function (linear, quadratic, exponential, trigonometric, etc.) is constructed that reflects a known or suspected physical pattern manifested in a given experiment, expressed in the form of an appropriate formula. IN laboratory workshop There are two cases: carrying out a theoretical graph has the goal of extracting unknown parameters of a function from an experiment (the tangent of the slope of a straight line, the exponent, etc.) or a comparison is made between the predictions of the theory and the results of the experiment.

In the first case, the graph of the corresponding function is drawn “by eye” so that it passes through all error areas as close as possible to the experimental points. There are mathematical methods, allowing the theoretical curve to be drawn through the experimental points in a certain sense in the best possible way. When drawing a graph “by eye,” it is recommended to use the visual sensation that the sum of positive and negative deviations of points from the drawn curve is equal to zero.

In the second case, the graph is constructed based on the results of calculations, and the calculated values ​​are found not only for those points that were obtained in the experiment, but with a certain step throughout the entire measurement area to obtain a smooth curve. Drawing the results of calculations in the form of points on graph paper is a working moment - after drawing the theoretical curve, these points are removed from the graph. If the calculation formula includes an already defined (or previously known) experimental parameter, then calculations are carried out both with the average value of the parameter and with its maximum and minimum (within the error) values. In this case, the graph shows a curve obtained with the average value of the parameter, and a band limited by two calculated curves for the maximum and minimum values ​​of the parameter.

Let's look at the rules for constructing graphs using the following example. Let us assume that the law of motion of a certain body was studied in an experiment. The body moved in a straight line, and the objective of the experiment was to measure the distance that the body travels over various periods of time. After conducting a certain number of experiments and processing the measurement results, the average values ​​of the measured quantities and their errors were found. It is required to display the experimental results presented in the table in the form of a graph and find from the graph body, assuming uniform motion.

Table. Dependence of the path traveled by a body on time

The material is a set for laboratory exercises for the work program academic discipline ODP.02 "Physics". The work contains explanatory note, assessment criteria, list of laboratory works and didactic material.

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Ministry of General Vocational Education

Sverdlovsk region

State autonomous educational institution

secondary vocational education

Sverdlovsk region "Pervouralsk Polytechnic"

LABORATORY WORK

TO THE WORK PROGRAM

ACADEMIC DISCIPLINE

EDP ​​02. PHYSICS

Pervouralsk

2013

Preview:

Explanatory note.

Laboratory tasks are designed in accordance with work program academic discipline "Physics".

Purpose of laboratory work: formation of subject and meta-subject results of students mastering the main educational program basic course physics.

Objectives of laboratory work:

No.	Generated results	Federal State Educational Standards requirements	Basic competencies
	Possession of educational and research skills.	Meta-subject results	Analytical
	Understanding the physical essence of observed phenomena.	Subject results	Analytical
	Possession of fundamental physical concepts, patterns, laws.	Subject results	Regulatory
	Confident use of physical terminology and symbolism	Subject results	Regulatory
	Knowledge of the basic methods of scientific knowledge used in physics: measurement, experiment	Subject results	Analytical
	Ability to process measurement results.	Subject results	Social
	The ability to detect relationships between physical quantities.	Subject results	Analytical
	Ability to explain results and draw conclusions.	Subject results	Self-improvement

The laboratory work report form contains:

1. Job number;
2. Purpose of the work;
3. List of equipment used;
4. Sequence of actions performed;
5. Drawing or installation diagram;
6. Tables and/or charts for recording values;
7. Calculation formulas.

Evaluation criteria:

Demonstration of skills.	Grade
Installation assembly (schemes)	Settings devices	Removal testimony	Calculation values	Filling tables, building graphs	Conclusion By work
						"5"
						"4"
						"3"

List of laboratory works.

Job no.	Title of work	Section title
	Determination of spring stiffness.	Mechanics.
	Determination of friction coefficient.	Mechanics.
	Studying the movement of a body in a circle under the action of gravity and elasticity.	Mechanics.
	Measuring gravity acceleration with Using a mathematical pendulum.	Mechanics.
	Experimental verification of Gay-Lussac's law.
	Surface Ratio Measurement tension.	Molecular physics. Thermodynamics.
	Measuring the elastic modulus of rubber.	Molecular physics. Thermodynamics.
	Study of the dependence of current strength on voltage.	Electrodynamics.
	Resistivity measurement conductor.	Electrodynamics.
	Study of the laws of sequential and parallel connection conductors.	Electrodynamics.
	Measurement of EMF and internal current source resistance.	Electrodynamics.
	Observation of action magnetic field on Current.	Electrodynamics.
	Observation of light reflection.	Electrodynamics.
	Refractive Index Measurement glass	Electrodynamics.
	Measuring the wavelength of light.	Electrodynamics.
	Observation of line spectra.
	Study of tracks of charged particles.	Atomic structure and quantum physics.

Preview:

Laboratory work No. 1.

"Determination of spring stiffness."

Target: Determine the stiffness of the spring using a graph of elastic force versus elongation. Draw a conclusion about the nature of this dependence.

Equipment: tripod, dynamometer, 3 weights, ruler.

Work progress.

1. Hang a load on a dynamometer spring, measure the elastic force and elongation of the spring.
2. Then attach the second one to the first weight. Repeat the measurements.
3. Attach the third to the second weight. Repeat the measurements again.

1. Plot a graph of the elastic force versus the elongation of the spring:

Fupr, N

0 0.02 0.04 0.06 0.08 Δl, m

1. Using the graph, find the average values ​​of elastic force and elongation. Calculate the average value of the elasticity coefficient:

1. Draw a conclusion.

Preview:

Laboratory work No. 2.

"Determination of the coefficient of friction."

Target: Determine the coefficient of friction using a graph of friction force versus body weight. Draw a conclusion about the relationship between the sliding friction coefficient and the static friction coefficient.

Equipment: block, dynamometer, 3 weights weighing 1 N each, ruler.

Work progress.

1. Using a dynamometer, measure the weight of the block R.
2. Place the block horizontally on the ruler. Using a dynamometer, measure the maximum static friction force Ftr 0 .
3. Evenly Moving the block along a ruler, measure the sliding friction force Ftr.
4. Place the weight on the block. Repeat the measurements.
5. Add a second weight. Repeat the measurements.
6. Add a third weight. Repeat the measurements again.
7. Enter the results in the table:

1. Plot graphs of friction force versus body weight:

Fupr, N

0 1.0 2.0 3.0 4.0 R, N

1. Using the graph, find the average values ​​of body weight, static friction force and sliding friction force. Calculate the average values ​​of the coefficient of static friction and the coefficient of sliding friction:

μav 0 = Fav.tr 0 ; μ av = Faver.tr;

RSR RSR

1. Draw a conclusion.

Preview:

Laboratory work No. 3.

"The study of the motion of a body under the influence of several forces."

Target: Study the movement of a body under the influence of elasticity and gravity. Draw a conclusion about the fulfillment of Newton's II law.

Equipment: tripod, dynamometer, 100 g weight on a string, circle of paper, stopwatch, ruler.

Work progress.

1. Hang the weight on a string using a tripod above the center of the circle.
2. Unwind the block in a horizontal plane, moving along the border of the circle.

R F control

1. Measure the time t during which the body makes at least 20 revolutions n.
2. Measure the radius of the circle R.
3. Take the load to the boundary of the circle, use a dynamometer to measure the resultant force equal to the elastic force of the spring F ex.
4. Using Newton's II law, calculate the centripetal acceleration:

F = m. a cs; and cs = v 2; v = 2. π. R ; T = _t_;

R T n

And cs = 4. π 2. R. n 2 ;

(π 2 can be taken equal to 10).

1. Calculate the resultant force m. A tss.
2. Enter the results in the table:

1. Draw a conclusion.

Preview:

Laboratory work No. 4.

"Measuring the acceleration of gravity."

Target: Measure the acceleration of gravity using a pendulum. Draw a conclusion about the coincidence of the obtained result with the reference value.

Equipment: tripod, ball on a string, dynamometer, stopwatch, ruler.

Work progress.

1. Hang the ball on a thread using a tripod.

1. Push the ball away from its equilibrium position.

1. Measure the time t during which the pendulum makes at least 20 oscillations (one oscillation is a deviation in both directions from the equilibrium position).

1. Measure the length of the ball suspension l.

1. Using the formula for the period of oscillation of a mathematical pendulum, calculate the acceleration of gravity:

T = 2.π. l ; T = _t_; _ t _ = 2.π. l ; _ t 2 = 4.π 2 . l

G n n g n 2 g

G = 4. π 2 . l. n 2 ;

(π 2 can be taken equal to 10).

1. Enter the results in the table:

1. Draw a conclusion.

Preview:

Laboratory work No. 5.

"An experimental test of Gay-Lussac's law."

Target: Investigate the isobaric process. Draw a conclusion about the fulfillment of Gay-Lussac's law.

Equipment: test tube, glass with hot water, glass of cold water, thermometer, ruler.

Work progress.

1. Place the test tube, open end up, in hot water to warm the air in the test tube for at least 2 to 3 minutes. Take your temperature hot water t 1 .
2. Close thumb hole of the test tube, remove the test tube from the water and place it in cold water, inverting the test tube. Attention! To prevent air from leaving the test tube, move your finger away from the hole of the test tube only under water.
3. Leave the test tube, open end down, in cold water for several minutes. Take your temperature cold water t 2 . Observe the rise of water in the test tube.

1. After the rise stops, equalize the surface of the water in the test tube with the surface of the water in the glass. Now the air pressure in the test tube is atmospheric pressure, i.e. the condition of the isobaric process P = const is satisfied. Measure the height of the air in the test tube l 2 .
2. Pour the water out of the test tube and measure the length of the test tube l 1 .
3. Check the implementation of Gay-Lussac's law:

V 1 = V 2; V 1 = _ T 1 .

T 1 T 2 V 2 T 2

The volume ratio can be replaced by the ratio of the heights of the air columns in the test tube:

l 1 = T 1

L 2 T 2

1. Convert the temperature from the Celsius scale to the absolute scale: T = t + 273.
2. Enter the results in the table:

1. Draw a conclusion.

Preview:

Laboratory work No. 6.

"Measurement of surface tension coefficient".

Target: Measure the surface tension coefficient of water. Draw a conclusion that the obtained value coincides with the reference value.

Equipment: pipette with divisions, a glass of water.

Work progress.

1. Fill the pipette with water.

1. Pour water from the pipette drop by drop. Count the number of drops n corresponding to a certain volume of water V (for example, 0.5 cm 3 ), poured out of the pipette.

1. Calculate the surface tension coefficient: σ = F , where F = m. g; l = π .d

σ = m. g, where m = ρ.V σ = ρ.V. g

π .d n π .d . n

ρ = 1.0 g/cm 3 – density of water; g = 9.8 m/s 2 – free fall acceleration; π = 3.14;

d = 2 mm – diameter of the drop neck, equal to the internal cross-section of the pipette nose.

1. Enter the results in the table:

1. Compare the obtained value of the surface tension coefficient with the reference value: σ Ref. = 0.073 N/m.

1. Draw a conclusion.

Preview:

Laboratory work No. 7.

"Measurement of the elastic modulus of rubber."

Target: Determine the elastic modulus of rubber. Draw a conclusion about the coincidence of the obtained result with the reference value.

Equipment: tripod, piece of rubber cord, set of weights, ruler.

Work progress.

1. Suspend the rubber cord using a tripod. Measure the distance between the marks on the cord l 0 .
2. Attach weights to the free end of the cord. The weight of the loads is equal to the elastic force F arising in the cord during tensile deformation.
3. Measure the distance between the marks when the cord is deformed l.

1. Calculate the elastic modulus of rubber using Hooke's law: σ = E. ε, where σ = F

– mechanical stress, S =π. d 2 - cross-sectional area of ​​the cord, d – diameter of the cord,

ε = Δl = (l – l 0 ) – relative elongation of the cord.

4. F = E. (l – l 0 ) E = 4 . F. l 0, where π = 3.14; d = 5 mm = 0.005 m.

π. d 2 l π.d 2 .(l –l 0 )

1. Enter the results in the table:

1. Compare the obtained elastic modulus value with the reference value:

E spr. = 8 . 10 8 Pa.

1. Draw a conclusion.

Preview:

Laboratory work No. 8.

"Study of the dependence of current on voltage."

Target: Construct the current-voltage characteristic of a metal conductor, use the obtained dependence to determine the resistance of the resistor, and draw a conclusion about the nature of the current-voltage characteristic.

Equipment: Battery of galvanic cells, ammeter, voltmeter, rheostat, resistor, connecting wires.

Work progress.

1. Take readings from the ammeter and voltmeter, adjusting the voltage across the resistor using a rheostat. Enter the results into the table:

U, V
I, A

1. Based on the data from the table, construct the current-voltage characteristic:

I, A

U, V

0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8

1. Using the current-voltage characteristics, determine the average values ​​of current Iav and voltage Uav.

1. Calculate the resistance of a resistor using Ohm's law:

Usr

R = .

Isr

1. Draw a conclusion.

Preview:

Laboratory work No. 9.

"Measurement of conductor resistivity."

Target: Determine the resistivity of the nickel conductor and draw a conclusion that the obtained value coincides with the reference value.

Equipment: Battery of galvanic cells, ammeter, voltmeter, nickel wire, ruler, connecting wires.

Work progress.

1) Assemble the chain:

A V

3) Measure the length of the wire. Enter the result into the table.

R = ρ. l/S – conductor resistance; S = π. d 2 / 4 – cross-sectional area of ​​the conductor;

ρ = 3.14. d2. U

4.I. l

d, mm	l, m	U, V	I, A	ρ, Ohm. mm 2/m
0,50

6) Compare the obtained value with the reference value of nickel resistivity:

0.42 Ohm.. mm 2 / m.

7) Draw a conclusion.

Preview:

Laboratory work No. 10.

"Study of series and parallel connection of conductors."

Target: Draw a conclusion about the fulfillment of the laws of series and parallel connection of conductors.

Equipment : Battery of galvanic cells, ammeter, voltmeter, two resistors, connecting wires.

Work progress.

1) Assemble the chains: a) with consistent and b) parallel connection

Resistors:

A V A V

R 1 R 2 R 1

2) Take readings from the ammeter and voltmeter.

R pr = ;

A) Rtr = R 1 + R 2; b) R 1 .R 2

R tr = .

(R 1 + R 2)

Enter the results into the table:

5) Draw a conclusion.

Preview:

Laboratory work No. 11.

“Measurement of EMF and internal resistance of a current source.”

Target: Measure the EMF and internal resistance of the current source, explain the reason for the difference between the measured EMF value and the nominal value.

Equipment: Current source, ammeter, voltmeter, rheostat, key, connecting wires.

Work progress.

1) Assemble the chain:

A V

2) Take readings from the ammeter and voltmeter. Enter the results into the table.

3 ) Open the key. Take readings from the voltmeter (EMF). Enter the result into the table. Compare the measured EMF value with the nominal value: ε nom = 4.5 V.

I. (R + r) = ε; I. R+I. r = ε; U+I. r = ε; I. r = ε – U;

ε – U

5) Enter the result into the table:

I, A	U, V	ε, V	r, Ohm

6) Draw a conclusion.

Preview:

Laboratory work No. 12.

"Observation of the effect of a magnetic field on a current."

Target: Determine the direction of the current in the coil using the left-hand rule. Draw a conclusion on what the direction of the Ampere force depends.

Equipment: Coil of wire, cell battery, key, connecting wires, arc-shaped magnet, tripod.

Progress of work.

1) Assemble the chain:

2) Bring the magnet to the coil without current. Explain the observed phenomenon.

3) Bring it to the coil with current first North Pole magnet (N), then – southern (S). Show in the figure the relative position of the coil and the poles of the magnet, indicate the direction of the Ampere force, the vector of magnetic induction and the current in the coil:

4) Repeat the experiments, changing the direction of the current in the coil:

S S

5 ) Draw a conclusion.

Preview:

Laboratory work No. 13.

"Observing the reflection of light."

Target:observe the phenomenon of light reflection. Draw a conclusion about the fulfillment of the law of light reflection.

Equipment:light source, screen with a slit, plane mirror, protractor, square.

Work progress.

1. Draw a straight line along which to place the mirror.

3. Point a beam of light at the mirror. Mark the incident and reflected rays with two dots. By connecting the dots, construct the incident and reflected rays, and at the point of incidence, use a dotted line to restore the perpendicular to the plane of the mirror.

1 1’

2 2’

3 3’

α γ

in the centersheet).

Using the screen, get a thin beam of light.

Shine a beam of light onto the plate. Mark with two points the incident ray and the ray emerging from the plate. By connecting the dots, construct the incident ray and the emerging ray. At the point of impact B, use a dotted line to restore the perpendicular to the plane of the plate. Point F is the point where the beam exits the plate. By connecting points B and F, construct a refracted ray BF.

A E

α

IN

β

D C

F

4. To determine the refractive index, we use the law of light refraction:

n=sin α

sin β

5. Construct a circlearbitraryradius (take the radius of the circle as possiblemore) with center at point B.
6. Designate the point A of the intersection of the incident ray with the circle and the point C of the intersection of the refracted ray with the circle.
7. From points A and C, lower perpendiculars to the perpendicular to the plane of the plate. The resulting triangles BAE and BCD are rectangular with equal hypotenuses BA and BC (radius of the circle).
8. Using the grating, obtain images of the spectra on the screen; to do this, examine the filament of the lamp through a slit in the screen.

1 max

b

φ a

0 max (gap)

diffraction

latticeb

1 max

screen

3. Using a ruler on the screen, measure the distance from the slit to the first-order red maximum.
4. Make a similar measurement for the first-order purple maximum.
5. Calculate the wavelengths corresponding to the red and violet ends of the spectrum using the diffraction grating equation: d. sin φ = k. λ, where d is the period of the diffraction grating.

d =1 mm = 0.01 mm = 1 . 10-2 mm = 1 . 10-5 m; k = 1; sin φ = tan φ =a(for small angles).

100 b

λ = d.b

A

6. Compare the results obtained with the reference values: λк = 7.6. 10-7 m; λf = 4.0. 10

   Laboratory work No. 16.

   "Observation of line spectra".

   Target:observe and sketch the spectra of noble gases. Draw a conclusion about the coincidence of the obtained spectral images with the standard images.

   Equipment:power supply, high-frequency generator, spectral tubes, glass plate, colored pencils.

   Work progress.

   1. Obtain an image of the spectrum of hydrogen. To do this, examine the luminous channel of the spectral tube through the non-parallel faces of the glass plate.
   2. Sketch the spectrumhydrogen (H):

   400 600 800, nm

   3. Similarly, obtain and sketch images of the spectra:

   krypton (Kr)

   400 600 800, nm

   helium (He)

   400 600 800, nm

   neon (Ne)

   1. Translate the particle tracks into a notebook (through glass),placing them in the corners of the page.
   2. Determine the radii of curvature of the tracks RI, RII, RIII, RIV. To do this, draw two chords from one point of the trajectory, constructmiddleperpendiculars to the chords. The point of intersection of the perpendiculars is the center of curvature of the track O. Measure the distance from the center to the arc. Enter the obtained values ​​into the table.

   R R

   ABOUT

   3. Determine the specific charge of the particle by comparing it with the specific charge of the proton H11 q = 1.

   m

   A charged particle in a magnetic field is acted upon by the Lorentz force: Fl = q. B.v. This force imparts centripetal acceleration to the particle: q. B. v = m.v2 qproportional1 .

   R m R

   -