Target– to determine the moment of inertia of the body by the method of torsional vibrations.

Devices and materials: measuring installation, set of bodies, stopwatch.

Description of installation and measurement method

The measuring setup is a round disk suspended on an elastic steel wire and designed to accommodate bodies, the moment of inertia of which should be determined (Fig. 8.1).

Rice. 8.1

The device is centered using two movable weights fixed on the disk. Turning the disk of the device at a certain angle around the vertical axis, the steel suspension is twisted.

When the body rotates through an angle , the wire twists and a moment of forces arises M seeking to return the body to a position of equilibrium. The experiment shows that in a fairly wide range the moment of forces M proportional to the angle of twist  , i.e.
(compare: elastic force
). The disk is released, allowing it to perform torsional vibrations. The period of torsional vibrations is determined by the expression
, where f– torsion modulus; J is the moment of inertia of the oscillating system.

For instrument
. (8.1)

Equality (8.1) contains two unknown quantities f and J etc. Therefore, it is necessary to repeat the experiment, after placing a reference body with a known moment of inertia on the setup disk. A solid cylinder is taken as a standard, the moment of inertia of which is J this .

Having determined the new oscillation period of the device with the standard, we compose an equation similar to equation (8.1):

. (8.2)

Solving the system of equations (8.1) and (8.2), we determine the torsion modulus f and the moment of inertia of the device J etc with this load position. (Derivation of calculation formulas for f and J etc do it yourself in preparation for the laboratory work and include it in the report). Having removed the standard, a body is placed on the disk of the device, the moment of inertia of which relative to the axis of the device must be determined. The installation is centered and the period of torsional vibrations is determined again T 2 , which in this case can be written as

. (8.3)

Knowing and f, calculate the moment of inertia of the body relative to the axis of the device based on formula (8.3).

The data of all measurements and calculations are entered in table. 8.1.

Table 8.1

Measured and calculated quantities for determining the moment of inertia using the torsional vibration method

	t etc	T etc	t 1	T 1	t 2	T 2
		< T etc >=	< T 1 >= < ¦ >= < J etc >=	< T 2 >= < J t >

Task 1. Determination of the periods of torsional vibrations of a device, a device with a standard, a device with a body

1. Measure the time with a stopwatch t etc 20-30 complete vibrations of the device and determine
.

2. Repeat the experiment 5 times and determine < T etc > .

3. Place a standard on the disk of the device and similarly determine < T 1 >.

4. Place the body on the disk of the device, center the installation, determine < T 2 > .

Record the measurement results in table. 8.1

Laboratory work №8.

"Measurement of the diameter and shape deviations of the hole surface with an indicator inside gauge".

The purpose of the work: To master the methods of measurement with an indicator caliper

hole diameters and hole shape deviations.

Task: Measure the diameter and shape deviations of the surface

holes in bushing-type parts with an indicator caliper.

Equipment: Indicator caliper with a head.

End measures of length (KMD).

Accessories for KMD.

Details of the bushing type and its drawing.

1. Theoretical part

Hole measurements are acceptable if ≤ i.e. the limiting error of measuring the head is less than the permissible error of measuring the hole.

2. Indicator caliper.

Tube 4 (Fig. 1) with a heat-insulating handle 6 serves as the basis of the indicator caliper. The upper opening of the tube with clamp 8 is used to install the sleeve of the measuring head or the dial indicator.

In the lower part of the tube there is an inside gauge head, consisting of a body 9, a centering bridge 11 and measuring rods-tips - movable 1 and rigid 10. The movement of the tip 1 through the lever 2, the stem 3 and the worm 5 is transmitted to the measuring head. Centering bridge 2 sets the measurement axis of the inside gauge (tip axis a1 and 10) to coincide with the diameter of the hole of the measured part (Fig. 2)

When measuring, it is necessary to shake the inside gauge in the axial plane in the longitudinal section and find the minimum position along the arrow of the measuring head, i.e. perpendicular to both generators of the hole.

Inside gauges with a centering bridge are produced with a measurement range: mm: 6…10; 10…18; 18…50; 50…100; 100…160; 160…250; 250…450; 450…700; 700…1000.

To measure holes of small diameters, inside gauges with ball inserts are accepted (Fig. 3) ball inserts have ranges: mm: 3 ... 6; 6…10; 10…18.

To set the indicator inside gauges to "0", adjusting rings or sets of end measures (KMD) and sidewalls are used. The KMD block is selected and installed in the holder along with the sidewalls. The operation when set to "0" is the same as when measuring a workpiece.

2.1 Measuring head.

The measuring head converts small movements of the measuring tip into large movements of the pointer of the reporting device.

Figure 4 shows a dial indicator. Measuring rod 1 of the indicator has a rail that engages with gear wheel 5 and transmits movement to tube 9 and arrows 8 through gear wheel 9. To set it to “0”, the round scale of the dial rotates together with rim 2. Arrow 6 shows the number of turns of arrow 8.

Dial gauges have a sleeve diameter of 8mm, a measuring rod stroke of 2; 5 or 10mm and a division price of 0.01mm.

In lever-toothed measuring heads, the movement of the measuring tip (turns) through the lever system is transmitted to the gear sector, which turns the gear wheel and the arrow sitting on the wheel axle. The heads have a division value of 0.001 mm and 0.002 mm, a measurement range of ± 0.05 mm ... 5 mm (multi-turn).

2.2 Preparation for measurement.

1. Fix the measuring head in the bore gauge tube. To do this, insert the sleeve of the measuring head into the hole of the tube so that the ball of the measuring tip touches the end of the rod and the dial scale is turned to the side with the centering bridge and secure the measuring head with a clamp, while the arrow should make a full turn. At the same time, it is necessary to maintain freedom of movement of the measuring rod of the head.

2. Dial the CMD block according to the nominal size of the hole and fix it between the sides in the CMD holder. Pre-wiping the tiles and sidewalls with gasoline. Wipe the weathered hole surface with a clean cloth.

3. check for compliance of the measurement limits of the inside gauge with the size of the measuring hole. If they do not match, replace the interchangeable measuring rod or select a set of extensions and washers for a rigid compound rod (depending on the type of inside gauge).

2.3 Setting the inside gauge to "0".

1. Take the inside gauge by the heat-insulating handle and insert the depth gauge between the sides.

2. Watching the arrow of the head and moving the inside gauge between the sides by swinging and rotating around the axis of the tube (see diagram), set the inside gauge to the position that matches the smallest distance between the measuring surfaces of the sides. In this case, the arrow will reach the farthest * (clockwise) division and turn back. For both types of movement (swinging and turning), this division must match.

3. Remember this division, remove the caliper from the sidewalls and turn the scale to the noted position with the rim of the dial (or the setting screw to “0”).

4.Check setting to "0". In the right position, the indicator needle should point to 0.

2.4 Hole diameter measurement.

1. Take the caliper with your right hand by the heat-insulating handle and, holding the part with your left hand, insert the caliper into the hole of the measured part with the measuring head up and the scale towards you. To do this, a movable rod with a bridge must be inserted to a shallow depth by tilting the inside gauge, and then straighten it so that the rigid rod rests against the opposite wall of the hole.

2. Move the caliper to the desired section and, shaking it in a vertical plane away from you - towards you, notice the farthest division of the scale, to which the arrow reaches.

A clockwise deviation of the arrow from “0” indicates a decrease in the hole diameter and a “-” sign, and a counterclockwise deviation indicates a decrease in diameter and a “+” sign.

4. Take the reading of the caliper, taking into account the scale division of the head and the sign, and write it down in the reference table. Measurements should be taken for each section in two mutually perpendicular directions.

Rice. 1Indicator caliper

Rice. 4 Dial indicator

3. Measurement results.

1. Taking into account the nominal size of the KMD block, calculate the actual dimensions of the part.

2. Compare the dimensions of the part with the allowable limiting dimensions and give a conclusion on the suitability of the part.

Having considered the dimensions of the part by sections, determine the deviations of the shape of the part from cylindricity.

3.Fill out a report on the work.

After checking the measurement results by the teacher, wipe the caliper, head, KMD and accessories to them with a dry cloth and put them in cases. Tidy up the workplace.

MINISTRY OF EDUCATION OF THE RUSSIAN FEDERATION

SIBERIAN STATE AEROSPACE UNIVERSITY

named after academician M.F. Reshetnev

Department of Technical Physics

Lab #8

FOUR-PROBE METHOD FOR MEASURING THE RESISTANCE OF SEMICONDUCTORS

Guidelines for performing laboratory work on the course "Solid State Electronics"

Compiled by: Parshin A.S.

Krasnoyarsk 2003

Laboratory work №8. Four-probe method for measuring the resistance of semiconductors1

Method theory . 1

Experimental setup . 3

Work order .. 5

Report formatting requirements . 7

test questions .. 7

Literature . 7

Laboratory work №8. Four-probesemiconductor resistance measurement method

Objective: study of the temperature dependence of the specific electrical resistance semiconductor by the four-probe method, determination of the band gap of a semiconductor.

Method theory

Four-probe the method of measuring the resistivity of semiconductors is the most common. The advantage of this method is that its application does not require the creation of ohmic contacts to the sample; it is possible to measure the resistivity of samples of the most diverse shapes and sizes. The condition for its use in terms of the shape of the sample is the presence of a flat surface, the linear dimensions of which exceed the linear dimensions of the probe system.

The circuit for measuring resistance by the four-probe method is shown in fig. 1. Four metal probes with a small contact area are placed along a straight line on the flat surface of the sample. Distances between probes s 1 , s2 and s3 . Through external probes 1 and 4 pass electric current I 14 , on internal probes 2 and 3 measure the potential difference U 23 . By measured values I 14 and U 23 the resistivity of a semiconductor can be determined.

To find the calculation formula for resistivity, let us first consider the problem of potential distribution around a separate point probe (Fig. 2). To solve this problem, it is necessary to write the Laplace equation in a spherical coordinate system, because the potential distribution has spherical symmetry:

.(1)

The solution of equation (1) provided that the potential at r=0 positive, tends to zero, at very large r has the following form

Integration constant With can be calculated from the condition for the electric field strength E some distance from the probe r=r0 :

.

Since the density of the current flowing through a hemisphere with a radius r0 , j =I/(2πr0 2), and in accordance with Ohm's law j =E/ρ , then E(r0)=I ρ / (2π r0 2).

Thus

If the contact radius r1 , then the potential of its tip

It is obvious that the potential on the sample at the point of its contact with the probe has the same value. According to formula (3), it follows that the main voltage drop occurs in the near-contact region and, therefore, the value of the current flowing through the sample is determined by the resistance of the near-contact region. The length of this region is the smaller, the smaller the radius of the probe.

The electric potential at any point of the sample can be found as the algebraic sum of the potentials created at that point by the current of each probe. For the current flowing into the sample, the potential is positive, and for the current flowing out of the sample, it is negative. For the probe system shown in fig. 1, the potentials of the measuring probes 2 and 3

;

.

Potential difference between measuring contacts 2 and 3

Hence the resistivity of the sample

.(5)

If the distances between the probes are the same, i.e. s 1 =s 2 =s 3 =s , then

Thus, to measure the specific electrical resistance sample using the four-probe method, it is enough to measure the distance between the probes s , voltage drop U 23 on the measuring probes and the current flowing through the sample I 14 .

Experimental setup

The measuring setup is implemented on the basis of a universal laboratory stand. The following devices and equipment are used in this laboratory work:

1. Heat chamber with sample and measuring head;

2. DC source TES-41;

3. DC voltage source B5-47;

4. Universal digital voltmeters V7-21A;

5. Connecting wires.

The block diagram of the experimental setup is shown in fig. 3.

The sample is placed on the measuring stage of the heat chamber. The measuring head is pressed by the spring mechanism of the manipulator to the flat polished surface of the sample. Inside the measuring table there is a heater, which is powered by a stabilized direct current source TES-41, operating in the current stabilization mode. The sample temperature is controlled by a thermocouple or thermal resistance. To speed up the measurement process, you can use the graduated curves presented in the appendix, which allow you to determine the temperature of the sample from the heater current. The heater current value is measured by an ammeter built into the current source.

Current through contacts 1 and 4 is created using an adjustable stabilized DC source B7-47 and controlled by a universal digital device V7-21A, switched on in the ammeter mode. The voltage that occurs between the measuring probes 2 and 3 is recorded by a high-resistance digital voltmeter V7-21A. Measurements must be carried out at the lowest current through the sample, determined by the possibility of measuring low voltages. At high currents, heating of the sample is possible, which distorts the measurement results. Reducing the operating current simultaneously reduces the modulation of the sample conductivity caused by the injection of charge carriers during the current flow.

The main problem in measuring electrical resistance probe methods is the problem of contacts. For high-vacuum samples, it is sometimes necessary to carry out electrical forming of contacts to obtain low contact resistances. Forming the contacts of the measuring probe is carried out by briefly applying a constant voltage of several tens or even hundreds of volts to the measuring probe.

Work order

1. Familiarize yourself with the description of the devices necessary to perform the work. Assemble the scheme of the measuring setup according to fig. 3. When connecting universal voltmeters V7-21A, pay attention that one must work in the voltage measurement mode, the other - in the current measurement. In the diagram, they are indicated by icons. " U" and " I" respectively. Check the correct setting of the mode switches on these devices.

2. After checking the correctness of the assembly of the measuring installation by the teacher or engineer, turn on the voltmeters and the B7-47 voltage source.

3. Set the voltage of the B7-47 source to 5V. If the voltage and current on the sample changes with time, then with the help of teachers or an engineer, electrical molding of the contacts of the measuring probe.

4. Carry out voltage drop measurements U+ 23 and U– 23 for different current directions I 14 . The obtained voltage values ​​are averaged for th, in order to exclude in this way the longitudinal thermo-EMF arising on the sample due to the temperature gradient. Enter the data of the experiment and calculations of stress values ​​in Table 1.

Table form 1

	I load, A	T,K	I 14, mA	U + 23 , AT	U – 23 , AT

5. Repeat measurements at a different sample temperature. To do this, you need to set the current of the heater of the thermal chamber I load,= 0.5 A, wait 5–10 minutes for the sample temperature to stabilize, and record the instrument readings in Table 1. Determine the sample temperature using the calibration curve presented in the Appendix.

6. Similarly, make measurements sequentially for heater current values ​​of 0.9, 1.1, 1.2, 1.5, 1.8 A. Record the results of all measurements in Table 1.

7. Process the obtained experimental results. To do this, using the results presented in Table 1, calculate 10 3 /T , specific electrical resistance sample at each temperature ρ according to formula (6), electrical conductivity

natural logarithm of electrical conductivity ln σ . Record all calculation results in Table 2.

Table form 2

	T,K	, K-1	ρ, Ohm m	σ, (Ohmm) -1	log σ

8. Build a dependency graph. Analyze the course of the curves, mark the areas of impurity and intrinsic conductivities. a brief description of the task set in the work;

· measurement setup diagram;

· results of measurements and calculations;

· dependency graph;

· analysis of the obtained results;

· work conclusions.

test questions

1. Intrinsic and extrinsic semiconductors. Band structure of intrinsic and impurity semiconductors. bandgap width. Impurity activation energy.

2. Mechanism of electrical conductivity of intrinsic and extrinsic semiconductors.

3. Temperature dependence of the electrical conductivity of intrinsic semiconductors.

4. Temperature dependence of the electrical conductivity of impurity semiconductors.

5. Determination of the band gap and the activation energy of an impurity from the temperature dependence of the electrical conductivity.

6. Four-probe Method of measurement electrical resistance semiconductors: scope, its advantages and disadvantages.

7. The problem of the distribution of the potential of the electric field near the probe.

8. Derivation of the calculation formula (6).

9. Scheme and principle of operation of the experimental setup.

10. Explain the experimentally obtained dependence graph, how was the band gap determined from this graph?

Literature

1. Pavlov L.P. Methods for measuring the parameters of semiconductor materials: A textbook for universities. - M .: Higher. school., 1987.- 239 p.

2. Lysov V.F. Workshop on semiconductor physics. –M .: Enlightenment, 1976.- 207 p.

3. Epifanov G.I., Moma Yu.A. Solid State Electronics: Tutorial. for university students. - M .: Higher. school., 1986.- 304 p.

4. Ch. Kittel, Introduction to Solid State Physics. - M.: Nauka, 1978. - 792 p.

5. Shalimova K.V. Semiconductor Physics: Textbook for High Schools. - M .: Energy, 1971. - 312 p.

6. Fridrikhov S.A., Movnin S.M. Physical foundations of electronic technology: A textbook for universities. - M .: Higher. school ., 1982.- 608 p.

Laboratory work 8 Measuring the power and work of the current in an electric lamp The purpose of the work is to learn how to determine the power and work of the current in a lamp using an ammeter, voltmeter and clock Equipment - a battery, a key, a low-voltage lamp on a stand, an ammeter, a voltmeter, connecting wires, a stopwatch.

Theory Formula for calculating the work of the current A= IUt Formula for calculating the power of the current P= IU or P= Division value = ___= A of the ammeter Division value =___= V of the voltmeter P theor. =U theor. I theor. / calculated from the U and I values ​​indicated on the light bulb base / Electrical circuit diagram

Calculations: A= P = A theor. = P theor. = Conclusion: Today in the laboratory work I learned how to determine the power and work of the current in the lamp using an ammeter, voltmeter and stopwatch. Calculated (a) the values ​​of the work of the current and the power of the light bulb: A \u003d J R \u003d W (indicate specific experimental values ​​​​of physical quantities). Also calculated (a) the theoretical values ​​of the work of the current and the power of the light bulb: A theor. = J R theor. \u003d W The experimental values ​​of the work and the current power in the lamp (approximately) coincide with the calculated theoretical values. Therefore, when performing laboratory work, small measurement errors were made. (The obtained experimental values ​​of the work and current power in the lamp do not coincide with the calculated theoretical values. Therefore, significant random measurement errors were made during the laboratory work.)

Lesson 47

Measuring the speed of uneven movement

Brigade __________________

__________________

Equipment: device for studying rectilinear motion, tripod.

Objective: prove that a body moving in a straight line on an inclined plane moves with uniform acceleration and find the value of the acceleration.

In the lesson, during a demonstration experiment, we made sure that if the body does not touch the inclined plane along which it moves (magnetic levitation), then its movement is uniformly accelerated. We are faced with the task of understanding how the body will move in the case when it slides along an inclined plane, i.e. between the surface and the body there is a friction force that prevents movement.

Let us put forward a hypothesis that the body slides along an inclined plane, also uniformly accelerated, and check it experimentally by plotting the dependence of the speed of movement on time. With uniformly accelerated motion, this graph is a straight line coming out of the origin. If the graph we have built, up to the measurement error, can be considered a straight line, then the movement on the investigated segment of the path can be considered uniformly accelerated. Otherwise, it is a more complex non-uniform movement.

To determine the speed within the framework of our hypothesis, we use the formulas of uniformly variable motion. If movement starts from rest, then V = at (1), where a- acceleration, t- travel time V- the speed of the body at a time t. For uniformly accelerated motion without initial velocity, the relation s = at 2 /2 , where s- the path traveled by the body during the movement t. From this formula a =2 s / t 2 (2). Substitute (2) into (1), we get: (3). So, to determine the speed of the body at a given point of the trajectory, it is sufficient to measure its movement from the starting point to this point and the time of movement.

Calculation of error limits. The speed is found from the experiment by indirect measurements. By direct measurements we find the path and time, and then according to the formula (3) the speed. The formula for determining the speed error limit in this case is: (4).

Evaluation of the results obtained. Due to the fact that there are errors in the measurements of distance and time, the values ​​of the velocity V do not lie exactly on a straight line (Fig. 1, black line). To answer the question of whether the studied motion can be considered uniformly accelerated, it is necessary to calculate the error limits of the speed change, plot these errors on the graph for each changed speed (red bars), draw a corridor (dashed lines),

Out of error limits. If this is possible, then such a movement with a given measurement error can be considered uniformly accelerated. The straight line (blue) coming from the origin of coordinates, located completely in this corridor and passing as close as possible to the measured values ​​of the speeds is the desired dependence of the speed on time: V = at. To determine the acceleration, you need to take an arbitrary point on the graph and divide the value of the speed at this point V 0 by the time at it t 0: a=V 0 / t 0 (5).

Working process:

1. We assemble the installation for determining the speed. We fix the guide rail at a height of 18-20 cm. We place the carriage at the very top of the rail and position the sensor so that the stopwatch turns on at the moment the carriage starts to move. The second sensor will be sequentially placed approximately at distances: 10, 20, 30, 40 cm for 4 experiments. The data is entered into a table.

2. We make 6 starts of the carriage for each position of the second sensor, each time entering the stopwatch readings into the Table. Table

Speed		Speed		Speed		Speed

3. We calculate the average value of the carriage movement time between the sensors - t cf.

4. Substituting the values ​​of s and t cf into formula (3), we determine the speeds at the points where the second sensor is installed. The data is entered into a table.

5. We build a graph of the dependence of the carriage speed on time.

6

Path and time measurement error:

∆s= 0.002 m, ∆t=0.01 s.

7. Using formula (4), we find ∆V for each speed value. In this case, the time t in the formula is t cf.

8. The found values ​​of ∆V are plotted on the graph for each plotted point.

. We build a corridor of errors and see if the calculated velocities V fall into it.

10. We draw a straight line V=at in the corridor of errors from the origin of coordinates and determine the acceleration value from the graph a according to formula (5): a=

Conclusion:__________________________________________________________________________________________________________________________________________

Lab #5

Lab #5

Determination of the optical power and focal length of a converging lens.

Equipment: ruler, two right-angled triangles, long focus converging lens, light bulb on a stand with a cap, current source, switch, connecting wires, screen, guide rail.

Theoretical part:

The simplest way to measure the refractive power and focal length of a lens is to use the lens formula

d is the distance from the object to the lens

f is the distance from the lens to the image

F - focal length

The optical power of the lens is called the value

As an object, a letter glowing with diffused light in the cap of the illuminator is used. The actual image of this letter is obtained on the screen.

The image is real inverted enlarged:

The image is imaginary direct enlarged:

Approximate progress of work:

F=8cm=0.08m

F=7cm=0.07m

F=9cm=0.09m

Laboratory work in physics No. 3

Laboratory work in physics No. 3

11th grade students "B"

Alekseeva Maria

Determination of free fall acceleration using a pendulum.

Equipment:

Theoretical part:

A variety of gravimeters, in particular pendulum devices, are used to measure the acceleration of free fall. With their help, it is possible to measure the acceleration of free fall with an absolute error of the order of 10 -5 m/s 2 .

The work uses the simplest pendulum device - a ball on a thread. For small ball sizes compared to the length of the thread and small deviations from the equilibrium position, the oscillation period is equal to

To increase the accuracy of the period measurement, it is necessary to measure the time t of a residually large number N of complete oscillations of the pendulum. Then the period

And the free fall acceleration can be calculated by the formula

Conducting an experiment:

Place a tripod on the edge of the table.

At its upper end, strengthen the ring with a coupling and hang a ball on a thread to it. The ball should hang at a distance of 1-2 cm from the floor.

Measure the length l of the pendulum with a tape.

Excite the oscillations of the pendulum by deflecting the ball to the side by 5-8 cm and releasing it.

Measure the time t 50 of the pendulum oscillations in several experiments and calculate t cf:

Calculate the average absolute error of time measurement and enter the results in a table.

Calculate free fall acceleration using the formula

Determine the relative error of time measurement.

Determine the relative error in measuring the length of the pendulum

Calculate the relative measurement error g using the formula

Conclusion: It turns out that the acceleration of free fall, measured with a pendulum, is approximately equal to the tabular acceleration of free fall (g \u003d 9.81 m / s 2) with a thread length of 1 meter.

Alekseeva Maria, student of 11 “B” class gymnasium No. 201, Moscow

Physics teacher of gymnasium No. 201 Lvovsky M.B.

Lab #4

Lab #4

Measurement of the refractive index of glass

pupils of the 11th grade "B" Alekseeva Maria.

Objective: measurement of the refractive index of a glass plate shaped like a trapezoid.

Theoretical part: the refractive index of glass relative to air is determined by the formula:

Calculation table:

Calculations:

n pr1= AE1 / DC1 =34mm/22mm=1.5

n pr2= AE2 / DC2 =22mm/14mm=1.55

Conclusion: Having determined the refractive index of glass, we can prove that this value does not depend on the angle of incidence.

Lab #6

Laboratory work №6.

Measurement of a light wave.

Equipment: diffraction grating with a period of 1/100 mm or 1/50 mm.

Installation diagram:

1. Holder.

2. Black screen.

   Narrow vertical gap.

Purpose of work: experimental determination of a light wave using a diffraction grating.

Theoretical part:

A diffraction grating is a collection of a large number of very narrow slits separated by opaque spaces.

Source

The wavelength is determined by the formula:

Where d is the grating period

k is the order of the spectrum

The angle at which the maximum light is observed

Diffraction grating equation:

Since the angles at which the maxima of the 1st and 2nd orders are observed do not exceed 5 , one can use their tangents instead of the sines of the angles.

Hence,

Distance a counted along the ruler from the grate to the screen, the distance b– on the screen scale from the slit to the selected line of the spectrum.

The final formula for determining the wavelength is

In this work, the measurement error of wavelengths is not estimated due to some uncertainty in the choice of the middle part of the spectrum.

Approximate progress of work:

b=8 cm, a=1 m; k=1; d=10 -5 m

(Red color)

d is the grating period

Conclusion: Having experimentally measured the wavelength of red light using a diffraction grating, we came to the conclusion that it allows you to very accurately measure the wavelengths of light waves.

Lesson 43

Lesson 43

Measurement of body acceleration

Brigade ____________________

____________________

Purpose of the study: measure the acceleration of the bar along a straight inclined chute.

Devices and materials: tripod, guide rail, carriage, weights, time sensors, electronic stopwatch, foam pad.

Theoretical justification of the work:

We will determine the acceleration of the body according to the formula: , where v 1 and v 2 are the instantaneous velocities of the body at points 1 and 2, measured at times t 1 and t 2 , respectively. For the X axis, select the ruler located along the guide rail.

Working process:

1. We select two points x 1 and x 2 on the ruler, in which we will measure instantaneous speeds and enter their coordinates in Table 1.

Table 1.

Points on the X-axis for measuring instantaneous speed		Δx 1 \u003d x ’ 1 - x 1 Δх 1 = cm				Δx 2 \u003d x ’ 2 - x 2 Δх 2 = cm
Definition of time intervals	Δt 1 \u003d t ’ 1 - t 1 Δ t 1 = c			Δt 2 \u003d t ’ 2 - t 2 Δ t 2 = c
Determination of instantaneous speed	v 1 \u003d Δx 1 / Δt 1 v 1 = m/s		v 2 \u003d Δx 2 / Δt 2 v 2 = m/s		Δ v= m/s
Determination of the time interval between speed measurement points	Δ t= with
Determining carriage acceleration

2. Select on the ruler points x ’ 1 and x ’ 2 the end points of the intervals for measuring instantaneous velocities and calculate the lengths of the segments Δх 1 and Δх 2 .

3. Install the time measurement sensors first at the points x 1 and x ’ 1, start the carriage and record the measured time interval for the passage of the carriage between the sensors Δ t 1 to the table.

4. Repeat the measurement for the interval Δ t 2 , the time during which the carriage passes between points x 2 and x ’ 2, setting the sensors at these points and starting the carriage. The data will also be entered into a table.

5. Determine the instantaneous speeds v 1 andv 2 at points x 1 and x 2, as well as a change in speed between points Δ v, data is entered into a table.

6. Define the time interval Δ t\u003d t 2 - t 1, which the carriage will spend on passing the segment between points x 1 and x 2. To do this, we will place the sensors at points x 1 and x 2, and start the carriage. The time shown by the stopwatch is entered in the table.

7. Calculate the acceleration of the carriage a according to the formula. We put the result in the last row of the table.

8. We conclude what kind of movement we are dealing with.

Conclusion: ___________________________________________________________

___________________________________________________________________

9. We carefully disassemble the installation, hand over the work, and leave the class with a sense of accomplishment and dignity.

Laboratory work in physics №7

Pupils of the 11th grade "B" Sadykova Maria

Observation of continuous and line spectra.

Equipment: projector, spectral tubes with hydrogen, neon or helium, high-voltage inductor, power supply, tripod, connecting wires, glass plate with beveled edges.

Objective: with the necessary equipment, observe (experimentally) the continuous spectrum, neon, helium or hydrogen.

Working process:

We place the plate horizontally in front of the eye. Through the edges we observe on the screen the image of the sliding slit of the projection apparatus. We see the primary colors of the resulting continuous spectrum in the following order: violet, blue, cyan, green, yellow, orange, red.

This spectrum is continuous. This means that all wavelengths are represented in the spectrum. Thus, we found out that continuous spectra give bodies that are in a solid or liquid state, as well as highly compressed gases.

We see many colored lines separated by wide dark stripes. The presence of a line spectrum means that the substance emits light of only a certain wavelength.

Hydrogen spectrum: violet, blue, green, orange.

The brightest is the orange line of the spectrum.

Helium spectrum: blue, green, yellow, red.

The brightest is the yellow line.

Based on our experience, we can conclude that line spectra give all substances in the gaseous state. In this case, light is emitted by atoms that practically do not interact with each other. Isolated atoms emit strictly defined wavelengths.

Lesson 37

Lesson42 . Laboratory work №5.

The dependence of the strength of the electromagnet on the strength of the current

brigade ___________________

___________________

Objective: Determine the relationship between the strength of the current flowing through the coil of an electromagnet and the force with which the electromagnet attracts metal objects.

Devices and materials: core coil, ammeter, variable resistance (rheostat), dynamometer, power supply, nail, connecting wires, wrench, tripod with holder, metal stand for magnetic parts.

X work od:

1. Assemble the installation shown in the figure. Attach the holder tab to the top of the tripod. Clamp the top of the dynamometer in the holder as shown. Tie a thread to the nail so that it gets into the recess at the sharp end of the nail and does not come off it. On the opposite side of the thread, make a loop and hang the nail on the dynamometer hook.

Record the dynamometer readings. This is the weight of the nail, you will need it when measuring the strength of the magnet:

3. Assemble the electrical circuit shown in the figure. Do not turn on the power until the teacher checks the correct assembly.

4. Close the key and, by rotating the rheostat from the maximum left to the maximum right position, determine the range of the circuit current change.

The current changes from ___A to ____A.

5. Select three current values, the maximum and two smaller ones, and enter

Them in the second column of the table. You will conduct three experiments with each current value.

6. Close the circuit and set the ammeter with a rheostat to the first current value you choose.

7. Touch the core of the coil to the head of the nail hanging on the dynamometer. The nail stuck to the core. Lower the coil vertically down and follow the dynamometer readings. Take note of the dynamometer reading at the moment the coil breaks off and enter it in column F 1 .

8. Repeat the experiment two more times with this current strength. Enter the force values ​​on the dynamometer at the moment the nail is torn off in columns F 2 and F 3. They may differ slightly from the first one due to measurement inaccuracy. Find the average magnetic strength of the coil using the formula F cp \u003d (F 1 + F 2 + F 3) / 3 and enter the column "Average strength".

9. The dynamometer showed a force value equal to the sum of the weight of the nail and the magnetic force of the coil: F = P + F M . Hence the strength of the coil is F M \u003d F - P. Subtract the weight of the nail P from F cp and write the result in the "Magnetic force" column.

Number	Current I, A	Dynamometer readings F, N			Average force F cp , N	Magnetic force F M , N

10. Repeat the experiments twice with other currents and fill in the remaining cells of the table.

I,A 1. Plot the magnetic force F M from current strength I.

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