Write down the result of measuring the electrical voltage considering that. Tasks on determining the readings of electrical measuring instruments taking into account the error (grade 8)

2.4.2.1. Calculate the instrumental error and record the measurement result taking it into account: .

2.4.2.2. Find the methodological error:
, Where R i = 5 Ohm,

R V B 7-26 = 30 MOhm,
=1MOhm.

2.4.2.3. Determine the correction and error of the correction using the formulas:

;
.

2.4.2.4. The result, taking into account instrumental and methodological errors, is written as:

2.4.3. Processing current measurement results

2.4.3.1. Record the result taking into account the instrumental error.

2.4.3.2. Find the methodological error:

2.4.3.3. Determine the correction and error of the correction:

;
.

2.4.3.4. The result, taking into account instrumental and methodological errors, is written as:

Purpose of the work.

Measurement scheme.

Tables and graphs of measurement results.

Experiment processing results.

Conclusions and comments on the work.

2.6. Security questions:

Direct and indirect measurements.

Joint and cumulative measurements.

True, actual and measured values of a physical quantity.

What is the accuracy class of the device?

Causes of methodological errors.

LABORATORY ROBOT No. 3 MEASUREMENT OF RESISTANCE BY DIRECT AND INDIRECT METHODS

Purpose of the work : become familiar with measuring instruments; study the methodology for measuring resistance by direct and indirect methods and determining their errors.

Theoretical information

(given in laboratory work No. 2)

3.2. Preparing instruments for resistance measurement

3.2.1. V7-26

Switch the type of work switch to the position “ r" and check the zero position of the pointer with the sockets short-circuited " r" and "*" (Fig. 3.1). Then open the sockets and set the pointer (arrow) to the “∞” position on the scale
knob “Set. “∞”” (for
).

Set the switch for the type of work to the “
" Select the instrument scale.

3.3. Measuring resistance using the direct method

3.3.1 Install on the resistance magazine:

(Ohm),
(kOhm).

3.3.2. Connect R X to B7-26 (Fig. 2) and measure its value. End scale value R k =
Ohm (10 n – scale multiplier). Write down R change , R k , K P .

3.3.3. Connect R X to Shch4313 (Fig. 3) and measure its value. Write down the values R change , R k, coefficients a And b(see device passport), calculate the accuracy class K P device.

For the Shch4313 multimeter, the accuracy class is determined by the formula:

3.3.4. Taking into account the instrumental error, the measurement result with the V7-26 device should be written in the form:

Where R change– measured value, R K– final value of the instrument scale.

Record the measurement result using the Shch4313 device in the form:

3.3.6. Install on the resistance store R 2 = (kOhm) and follow steps 2.1. - 2.5.

3.4. Measuring resistances r1 and r2 using the indirect method

3.4.1. Assemble the circuit (Fig. 4). Install on power supply E= (B).

, . R V= 30 MOhm, I K– final scale value. Record the results of current and voltage measurements in the form:

Record the resistance measurement result R 1 (R 2 ) taking into account the instrumental error of indirect measurements:

,
. Amendment P = -R A .

Final resistance measurement result:

3.4.2. Assemble the circuit (Fig. 5). Record current and voltage measurements:

;
.

Record the measurement result taking into account the instrumental error

indirect measurements:

Methodological measurement error:

;
.

Correction for methodological error:

Random error correction
:

Result of resistance measurement taking into account errors:

5. Draw conclusions based on the results obtained.

Job source: Decision 2452.-18. OGE 2017 Physics, E.E. Kamzeeva. 30 options.

Task 17. A radioactive drug is placed in a magnetic field. This field is rejected

The correct answer is

1) only A; 2) only B; 3) both A and B; 4) neither A nor B

Solution.

Alpha and beta decays result in the emission of charged particles. These particles interact with the magnetic field and will be deflected by it. Therefore, we have answer option number 3.

Answer: 3.

Task 18. Write down the result of measuring the electrical voltage (see figure), taking into account that the measurement error is equal to the division value.

1) (1.4 ± 0.1) V

2) (1.4 ± 0.5) V

3) (2.4 ± 0.1) V

4) (2.8 ± 0.2) V

Solution.

The two scales of the voltmeter show that it can measure voltage in two ranges: from -1 to 3 V, and from -2 to 6 V. In the figure, the terminals are connected to the 0 and 3 V marks, therefore, we must focus on the lower scale. The lower scale division value of 0.1 V is the measurement error. The arrow shows 1.4 V, therefore we have 1.4 ± 0.1 V. Answer number 1.

Tasks on determining the readings of electrical measuring instruments taking into account the error

Task No. 1

An ammeter with a uniform scale of 50 divisions is designed to measure a current of 500 mA. What are its readings if the needle deviates by 40 divisions, and the error in direct measurement of current strength is half the value of the ammeter division.

Answer: (___± ____) mA

Task No. 2

What does the ammeter show taking into account the absolute error? The absolute error is taken equal to half the scale of the instrument

Answer: (_____ ± ____) A

Task No. 3

What are the readings of the ammeter if the error of direct measurement is equal to half the scale of the instrument?

Answer: (_____ ± ____) A

Task No. 4

Write down the result of measuring the electrical voltage, taking into account that the error is equal to half the division value. Please indicate reading and accuracy.

Answer: (_____ ± ____) IN

Task No. 5

What does the ammeter show taking into account the absolute error? The absolute error is taken equal to half the scale of the instrument.

Answer: (___± ____) mA

Task No. 6

What does the voltmeter show taking into account the absolute error? Take the absolute error equal to half the scale division of the instrument.

Preparing a child for the final certification in physics is not an easy task. You need a lot of work experience, a preparation algorithm that has been developed and tested over the years, and accumulated material. Selecting material on topics is not difficult, but it takes a lot of time, so it’s good when you can turn to your colleagues for help.

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Preview:

How much energy does an electric stove consume at a current of 6 A in 20 minutes if its coil resistance is 25 Ohms?

1)1,080,000 J 2)180,000 J 3)18,000 J 4)3,000 J

2. A rheostat is connected in series with the electric lamp. The voltage at the ends of the circuit is 220 V, the current in the circuit is 5 A. A voltmeter connected to the lamp shows 120 V. What is the resistance of the rheostat?

3.Three wires are connected as shown in the picture. Conductor resistances: R 1 = 10 Ohm, R 2 = 5 Ohm, R 3 = 5 Ohm. What is the voltage on conductor 1 if the ammeter shows a current of 2 A?

4.The figure shows the connection of two conductors. Which ammeter is correctly connected to measure the current flowing through conductor 1?

5.The figure shows the connection of two conductors. Which voltmeter is correctly turned on to measure the voltage on conductor 1?

1) only V 1 2) only V 2
3)V 3 only 4)V 1 and V 3

6.In straight nichrome wire with a cross-sectional area of 1 mm 2 The direct current is 1 A. What is the voltage between those points of this wire that are 2 m apart?

1)0.45 V 2)1.1 V 3)2 V 4)2.2 V

7. Write down the result of measuring the electrical voltage (see figure), taking into account that the measurement error is equal to the division value.

1)(1.4 ± 0.2) V 2)(1.4 ± 0.1) V 3)(2.8 ± 0.1) V 4)(2.8 ± 0.2) V

8 . What is the mass of water that can be heated with an electric boiler from a temperature of 20 0 C to boiling point within 20 minutes? Mains voltage 220 V, current 3.5 A.

9.The three conductors are connected as shown in the figure. Conductor resistances: R 1 = 6 Ohm, R 2 = 8 Ohm, R 3 = 8 Ohm. What current strength does the ammeter show if the voltage on the conductor R 1 equals 24 V?

1)16 A 2)8 A 3)4 A 4)2 A

10. The table presents the results of a study of the dependence of current on voltage at the ends of the resistor. What current value should be present in an empty cell?

U, V
I, A

1)4.3 A 2)4.5 A 3)5 A 4)6 A

1) through R 1 2) through R 2 3) through R 3 4 through R 4

1)36.8 Ohm 2)92 Ohm 3)230 Ohm 4)270 Ohm

3. Three wires are connected in parallel to the current source circuit: copper, iron, nickel. The cross-sectional areas and lengths of the wires are the same. When the key is closed, it will be highlighted in 1 s.

4. By changing the electrical voltage on a section of the circuit consisting of a nickel conductor with a cross-sectional area of 0.2 mm 2 , the student, using the data obtained, plotted a graph of current versus voltage. What is the length of the conductor?

5. In the electrical circuit shown in the diagram, the ammeter shows a current of 4 A, the voltage on the first conductor is 20 V. The voltmeter shows a voltage of 60 V. The resistance of the second conductor

1)10 Ohm 2)15 Ohm 3)160 Ohm 4)320 Ohm

6. What current does the ammeter show?

1)0.67 A 2)2.14 A 3)3 A 4)5 A

7. When the voltage in the network increases by 2 times, the amount of heat released per unit time in the conductor connected to the network,

1) will increase by 4 times 2) will decrease by 4 times 3) will increase by 2 times 4) will decrease by 2 times

8. The total resistance of the circuit section shown in the figure is 3 ohms. Resistor values R2 = R3 = 3 Ohm. What is the resistance? R1?

1)1.5 Ohm 2)2.34 Ohm 3)3.66 Ohm 4)4.4 Ohm

9. Determine the density of nickel wire with a cross-sectional area of 1 mm 2 and weighing 176 g, from which the rheostat is made, if at a voltage at its ends of 24 V, the current flowing is 3 A.

10. Calculate the length of nichrome wire with a cross-sectional area of 0.05 mm 2 , necessary for the manufacture of a 275 W heater spiral operating from a 220 V DC network. 1) 2 m 2) 4 m 3) 6 m 4) 8 m 11. three resistors, the resistances of which are: R 1 = 3 Ohm; R 2 = 6 Ohm and R 3 = 9 Ohm, connected in series. A voltmeter connected in parallel with the second resistor shows a voltage of 12 V. What is the voltage across the entire circuit? A voltmeter is considered ideal.

1) 648 V 2) 144 V 3) 36 V 4) 9 V

Preview:

1. To measure the current passing through the lamp and the electrical voltage across the lamp, the student assembled the electrical circuit shown in the figure.

wrong

2. To measure the current passing through the lamp and the electrical voltage across the lamp, the student assembled an electrical circuit shown in the figure.

Which devices (ammeter and (or) voltmeter) are included in the electrical circuit correctly? 1) Ammeter only 2) Voltmeter only 3) Both ammeter and voltmeter are turned on correctly 4) Both ammeter and voltmeter are turned on wrong

3. The student assembled the electrical circuit shown in the figure. Which statement is correct?

1) When the key is closed, the ammeter will show the current flowing through the voltmeter 2) When the key is closed, the voltmeter will show the electrical voltage on the resistor R2 3) When the key is closed, the voltmeter will show the electrical voltage on the rheostat R 4) When the key is closed, the ammeter will show the current flowing through the resistor R1

4.Which of the devices (ammeter and (or) voltmeter) are included in the electrical circuit correctly? 1)Ammeter only 2)Voltmeter only 3)Both ammeter and voltmeter are turned on correctly 4)Both ammeter and voltmeter are turned on wrong

5. The student assembled the electrical circuit shown in the figure. Which statement is correct? 1) When the key is closed, the ammeter will show the strength of the electric current flowing through the rheostat R 2) When the key is closed, the ammeter will show the strength of the electric current flowing through the resistor R1 3) When the key is closed, the ammeter will show the total strength of the electric current flowing through the resistors R1 and R2 4) The ammeter is connected to an electrical circuit in violation of the polarity of the connection

6. The student assembled the electrical circuit shown in the figure. Which statement is correct? 1) When the key is closed, the ammeter will show the strength of the electric current flowing through the rheostat R 2) When the key is closed, the ammeter will show the total strength of the electric current flowing through resistors R1 and R2 3) When the key is closed, the ammeter will show the strength of the electric current flowing through the resistor R2 4) The ammeter is connected to an electrical circuit in violation of the polarity of the connection

7. The student assembled the electrical circuit shown in the figure. Which statement is correct?

1) When the key is closed, the ammeter will show the strength of the electric current flowing through the rheostat R 2) When the key is closed, the voltmeter will show the electrical voltage on the rheostat R 3) When the key is closed, the voltmeter will show the total electrical voltage on resistors R1 and R2 4) The voltmeter is connected to the electrical circuit with connection polarity violation

8. The student assembled the electrical circuit shown in the figure. Which statement is correct? 1) When the key is closed, the ammeter will show the strength of the electric current flowing through the rheostat R 2) When the key is closed, the ammeter will show the strength of the electric current flowing through the resistor R1 3) When the key is closed, the ammeter will show the strength of the electric current flowing through the resistor R2 4) The ammeter is turned on electrical circuit is incorrect

Workbook

Electricity at the rate

Guidelines

all forms of education

Rostov-on-Don

Compiled by:

Introduction

Measurement limit

division price instrument scale according to the formula:

WITH = X pr/ N,

Where X pr - measurement limit, N- the total number of scale divisions.

n measured value:

X meas = With n.

accuracy class kX to the measurement limit X

Thus,

XX X Meas.:

Lab 1

Work order

3. Calculate the division price:

C 1 = U pr1 /N =

C 2 = U pr2 /N =

C 3 = U pr3 /N =

Enter the data into the table.

n 1 = n 2 = n 3 =

U meas.1 = C 1 n 1 =

U meas2 = C 2 n 2 =

U meas.3 = C 3 n 3 =

Round this value to the first significant figure.

U = U Measurement ± D U; d i = …%.

U 1= ± ; d U 1 = %.

U 2= ± ; d U 2 = %.

U 3= ± ; d U 3 = %.

Meaning U

Security questions

Lab 2

Measurement of physical quantities

Determination of capacitance

Electromotive force measurement

Definition of horizontal

Workbook

Electricity at the rate

Guidelines

for laboratory work in physics

for 1st and 2nd year students of technical specialties

all forms of education

Rostov-on-Don

Compiled by:

Candidate of Physical and Mathematical Sciences, Associate Professor V. A. Vagan

Candidate of Pedagogical Sciences, Associate Professor I. I. Dzhuzhuk

Candidate of Physical and Mathematical Sciences, Associate Professor B. B. Konkin

Candidate of Physical and Mathematical Sciences, Associate Professor V. P. Safronov

Candidate of Physical and Mathematical Sciences, Associate Professor V. V. Shegai

ELECTRICITY: Method. instructions for laboratory work in physics / DSTU GOU, Rostov n/d, 2011 - 48 p.

The necessary theoretical material, the procedure for performing work and control questions are given.

Designed for 1st and 2nd year students of technical specialties of all forms of study.

Introduction

Electrical measuring instruments have one or more measurement limits.

Measurement limit- this is the maximum value of the measured quantity that can be determined on the scale of the device.

Before starting measurements, you should calculate division price instrument scale according to the formula:

WITH = X pr/ N,

Where X pr - measurement limit, N- the total number of scale divisions.

Knowing the value of the instrument scale division and determining the number of divisions n, by which the instrument needle deviated during measurement, can be found measured value:

X meas = With n.

It should be remembered that the value n rounded to half of one minimum division.

All electrical appliances are characterized accuracy class k, which is equal to the ratio of the absolute error D X to the measurement limit X etc. The accuracy class is indicated on the instrument scale as a percentage.

Thus,

From this relationship it follows that the absolute error is equal to:

The measurement accuracy is characterized by the relative error d X, which is the ratio of the absolute error D X to the measured value X Meas.:

The relative error decreases with increasing measured value. Therefore, the measurement limit must be selected in such a way that the instrument needle deviates by the maximum number of divisions.

Lab 1

Electrical voltage measurement

Work order

The electrical circuit (see Fig. 1) has already been assembled on the stand.

3. Calculate the division price:

C 1 = U pr1 /N =

C 2 = U pr2 /N =

C 3 = U pr3 /N =

Enter the data into the table.

4. Lock the key. Write down the number of divisions on the voltmeter scale n, by which its arrow will deviate.

n 1 = n 2 = n 3 =

5. Determine the value of the measured voltage

U meas.1 = C 1 n 1 =

U meas2 = C 2 n 2 =

U meas.3 = C 3 n 3 =

6. Calculate the absolute error:

Round this value to the first significant figure.

7. Determine the measurement accuracy:

Round this value to the first significant figure.

8. Write the result in the form: U = U Measurement ± D U; d i = …%.

U 1= ± ; d U 1 = %.

U 2= ± ; d U 2 = %.

U 3= ± ; d U 3 = %.

Meaning U Round the measurement taking into account the absolute error.

9. Compare the measurement results at three different voltmeter measurement limits and explain their differences.

Security questions

1. What is the measuring limit of the device?

2. How to determine the scale division value of an electrical measuring instrument?

3. How to find the value of the measured quantity?

4. What is the accuracy class of the device called?

5. How is absolute and relative measurement error determined?

Lab 2