“Calculation of conductor resistance. Resistivity

Lesson summary

physics 8th grade

“Calculation of conductor resistance.

Resistivity"

Lesson topic. Dependence of conductor resistance on other physical quantities.

Lesson objectives (planned learning outcomes):

Personal:

    development of independence in acquiring new knowledge and practical skills;

    developing the ability to conduct dialogue on the basis of equal relations and mutual respect.

Metasubject: development of students' skills:

    independently determine the purpose of your work;

    evaluate the accuracy of the hypotheses from the point of view of the information obtained during the study;

    formulate your own opinion and position, argue and coordinate it with the positions of partners in cooperation when developing a common solution in joint activities;

    independently evaluate and analyze your own activities from the perspective of the results obtained.

Subject:

    formation of an idea of ​​the dependence of conductor resistance on physical quantities;

    developing the ability to plan and conduct an experiment, and formulate a conclusion based on the results of the experiment;

    developing the ability to apply knowledge about the dependence of conductor resistance on physical quantities to explain physical phenomena and solve applied problems.

Materials and equipment:

    laptops, projector and screen;

    computer presentation “Dependence of resistance on physical quantities”

    worksheet for conducting an experimental study (Appendix No. 1);

    worksheets to be completed on laptops during the experimental study, completed in the program;

    sheet of diagnostic test work (Appendix No. 2);

    applied tasks for homework (Appendix No. 3)

    markers and A3 sheet for each group.

    sets for experimental research: ammeter, voltmeter, current source, key, connecting wires, metal conductors:

    equal length and cross-sectional area, but different resistivity - 2 pcs.;

    made of the same material, having equal lengths, but different cross-sectional areas - 2 pcs.;

    made of the same material, having equal cross-sectional areas, but different lengths - 2 pcs.

During the classes.

    Motivation.

Goal: creating a problematic situation associated with a lack of knowledge about why it is impossible to replace connecting wires made of non-ferrous metals with others that would not attract the attention of intruders

Students

What is shown on the screen?

Electrical circuit diagram.

What are the main elements of an electrical circuit?

Current source, electrical energy consumers, closing devices, connecting wires.

What three quantities characterize an electrical circuit?

Symbols appear on the screen: I, U, R

Current, electrical voltage and electrical resistance.

What relationship exists between these quantities? Who made this connection? (How is Ohm's law read?)

Students' answers are heard, and the dependence of current on voltage and resistance and the formula of Ohm's law appear on the screen.

The current strength is directly proportional to the voltage at the ends of the conductor. The current in a conductor is inversely proportional to the resistance of the conductor.

The dependence of current on voltage and resistance was established by Georg Ohm in 1827.

To transmit electric current over a distance, connecting wires are used, which are mainly made of non-ferrous metals, for example aluminum.

There are frequent cases of theft of non-ferrous metals. Here’s what they write in the regional newspaper “Na Smenu”: “One of the main reasons for emergency and pre-emergency situations on gas pipelines, railways and in the energy industry today is theft. The electrical circuit, which contains a lot of copper and copper-containing elements, is also valuable to thieves, as well as the aluminum wires of power lines.

The state spends a lot of money on replacement and protection. Maybe this problem can be solved differently by replacing connecting wires made of non-ferrous metals with others that will not attract the attention of intruders?

We will write down our assumptions on a “cloud”. It's in front of you.

We see different points of view. The teacher reads out several options for hypotheses.

Students write down various versions of hypotheses, among which were, for example, the following:

    Wires cannot be replaced, since non-ferrous metals, unlike others, have lower resistance, which means better conductivity.

    Wires can be replaced, since conductivity does not depend on what material the conductor is made of.

    Wires cannot be replaced, since non-ferrous metals have special characteristics that increase electrical conductivity.

Maybe the work we do in the next step will help us test our assumptions and resolve the problem situation.

What do I need to do?

Conduct research.

Result: several variants of hypotheses appeared, which necessitated their testing. Students remembered the basic elements of an electrical circuit and its characteristics, established a relationship between them, a review of previously studied material will allow them to more confidently plan and conduct experimental research at the next stage of the lesson.

    Study.

Purpose: to establish in the course of an experimental study how this or that characteristic of the conductor affects the resistance.

Students

Where do you suggest starting your research? (What will be your actions?)

Establish what determines the resistance of conductors? From what physical quantities?

In physics lessons we use two types of research: theoretical and experimental. What kind of research do you enjoy doing most?

Today you have the opportunity to conduct an independent experimental study.

I prefer to conduct experimental research.

Students work in groups. The two groups work with conductors having equal lengths and cross-sectional areas and different resistivities.

Two groups work with conductors of the same material, having equal lengths but different cross-sectional areas

Two groups work with conductors of the same material, having equal cross-sectional areas but different lengths

Depending on the level of development of the ability to draw up a research plan, one group is given a plan for an experimental study. They need to complete the task, analyze the results and draw a conclusion. The research plan worksheet is presented in Appendix 1.

Experimental study design.

    Assemble the circuit using this equipment.

    Take ammeter and voltmeter readings when metal wires are connected to the data circuit and calculate the resistance.

    Enter the data into the computer.

    Compare resistances, find out what influenced the value of resistance.

    Draw a conclusion.

    Analyze graphical dependences of current on voltage and resistance.

Other groups are offered a higher level task:

    Analyze the proposed equipment.

    Create a plan for an experimental study and implement it.

    Enter the received data into the computer.

    Draw a conclusion in accordance with the data received.

Result: students in groups conducted an experimental study withconductors having different characteristics, based onthe results of the experiment formulated a conclusionabout the dependence of the resistance of a conductor on physical quantities, such as the length of the conductor, its cross-sectional area, as well as on the type of substance from which the conductor is made.

    Information exchange .

Purpose: to enable groups to present the results of their work to the whole class and organize a discussion of these results.

Groups completed worksheets on laptops. When the groups presented the results of their work, students were asked to pay attention to the completeness and correctness of the formulation of the conclusion based on the results of the experimental study.

Groups working with conductors that differ only in resistivity have concluded: Resistance depends on the material from which the conductor is made.

The following appears on the board: Rdepends on the type of substance

Groups working with conductors differing only in cross-sectional area have concluded: The larger the area (S), the greater the current (I), the lower the resistance (R).

Resistance is inversely proportional to cross-sectional area:R~ 1/ S

Groups working with conductors differing only in length came to the conclusion: The greater the length (l), the less the current (I), the greater the resistance (R).

Resistance is directly proportional to the length of the conductor:R~ l

Result: the presentation of the results of the work showed that all groups successfully completed the experimental study. The conclusions formulated by students based on the results are mostly presented in full. Students made additions as the results were presented, and others asked clarifying questions.

    Organizing and linking information .

Purpose: to connect the data obtained during the groups’ performances to formulate a conclusion about the dependence of conductor resistance on physical quantities. Establish the physical meaning of the resistivity of a conductor and formulate the conclusion that non-ferrous metals have lower resistivity, which means that, with other characteristics being equal, the resistance of wires made of non-ferrous metals will be less. Draw a conclusion about the correctness of the hypotheses.

Students

Formulate a general conclusion about the dependence of conductor resistance on physical quantities

The resistance of a conductor depends directly on the material from which it is made, on the length of the conductor, and in inverse proportion on the cross-sectional area.

When establishing the dependence of resistance on physical quantities, have we taken everything into account?

Students agreed, and some students suggested that resistance depends on temperature.

Indeed, there is a linear dependence of resistance on temperature. You can learn about it in the scientific literature; this addiction will be discussed in high school.

Using the data we obtained from the experimental study, can we write down a formula to calculate resistance?

Students offer their options.

R= k ____, where k is the coefficient

S proportionality,

which characterizes the substance from which the conductor is made

Specify what physical quantities are included in the formula and what are their units of measurement?

R – conductor resistance, [R] = Ohm;

l – length of the conductor, [ l] = m;

S – cross-sectional area,

[S] = mm 2, [S] = m 2.

The teacher addresses the presentation. Using presentation material, the teacher introduces the concept of conductor resistivity

r is the resistivity of the conductor. Write down the formula to calculate resistivity.

r = RS / l

What are the units of measurement for this quantity?

[r] = Ohm mm 2 /m; [r] = Ohm m 2 /m = Ohm m

We need to figure out what the physical meaning of this quantity is? What does this value determine in the formula?

Dependence of resistance on the type of substance

One of our groups worked with this addiction (the teacher refers to the results of the study).

What would happen to the resistance of a copper conductor if we took it 1 m long and with a cross-sectional area of ​​1 mm 2?

The conductor resistance was equal to the resistivity

What is conductor resistivity?

The resistivity of a conductor is the resistance of a conductor of a given substance, taken 1 m long and with a cross-sectional area of ​​1 mm2

Let's refer to the table on the screen (table of resistivity values ​​of various metals).

Determine the resistivity of copper, aluminum, and iron from the table. Compare them.

r copper = 0.0175 Ohm mm 2 /m

r aluminum = 0.03 Ohm mm 2 /m

r iron = 0.13 Ohm mm 2 /m

Non-ferrous metals have lower resistivity, which means that, with other characteristics being equal, the resistance of wires made of non-ferrous metals will be less.

Result: the general conclusion of the lesson was formulated and the students came to a consensus that non-ferrous metals, with other characteristics being equal, have less resistance than others.

    Reflection.

Goal: obtaining feedback and focusing students' attention on the importance of studying this topic.

Students

Let's go back to the beginning of the lesson. Who was close to the correct resolution of the problem situation?

The one who expressed the idea that non-ferrous metals, unlike others, have less resistance, and therefore better conductivity, turned out to be more right.

Is there a need to remove some hypotheses?

Students offer to remove some hypothesis bubbles.

What is the secret of your confidence in the answers?

At the beginning of the lesson, we correctly formulated the goal, determined the experimental research plan, were careful when conducting the experiment, and were able to detect the relationship between physical quantities.

What new information did you note for yourself?

The resistance of a conductor is affected by its length, cross-sectional area and the material from which it is made.

To transmit electricity over a distance, conductors made of non-ferrous metals can be used, since they have increased electrical conductivity.

Will the knowledge you learned in today's lesson be useful to you in life?

Students express different points of view, for example:

    Knowledge will allow us to explain why non-ferrous metals are the best conductors of electricity.

    Knowledge will help us identify materials that can be used to increase or decrease the resistance of a conductor.

Result: students’ awareness of the importance of studying this topic.

    Application.

Goal: use new knowledge to solve applied problems. Control and self-control of mastering new material.

Students are invited to complete tasks (Appendix No. 2) presented on computers that allow self-testing. Then you evaluate your work on the scale used to evaluate a similar task for State Examination -9 in physics: 1 point - there are no errors in the work and 0 points - an error was made.

Result: updating the acquired knowledge while solving applied problems. After completing the work, we discussed its results: 93% of students completed the tasks correctly. This indicates a fairly high level of students’ assimilation of educational material at the initial stage.

    Homework.

Students are asked to prepare a background summary on the topic of the lesson using § 45 and solve a design problem:

The use of electric current, or, as they say, electricity, is quite expensive, so we must use it rationally. For example, when dusk comes, we begin to resort to artificial lighting; the darker it is outside, the more lighting is required. But our lighting devices always operate in the same mode. (The teacher went to the switch and demonstrated the process of lighting the class.)

You are invited, using the material from today's lesson, to come up with a device with which you could change the intensity of the lamp.

To apply the knowledge acquired in the lesson, students are offered a choice of 2-3 tasks of an applied nature (Appendix No. 3), for example:

    Three wires of the same cross-section and length - copper, tungsten and lead - are connected in parallel to the battery circuit. Which one will carry the most current?

    A coil of constantan wire is 10 m long. How can you determine its cross-sectional area using an ammeter and voltmeter without unwinding the wire?

    There are two conductors of the same material. One conductor is three times longer than the other. A short conductor has twice the cross-sectional area. Which conductor has the greater resistance?

“Calculation of conductor resistance. Resistivity"

Lesson Objectives:

Educational: Create conditions that encourage self-educational activity

students, apply their knowledge in a new situation, develop the ability to solve

calculation tasks. Determine the dependence of the conductor resistance on its length,

cross-sectional area and the substance from which it is made.

Developmental: Develop elements of creative search based on the technique of generalizing knowledge, the ability to analyze, observe, assemble electrical circuits, draw diagrams, develop practical work skills, interest in the subject by performing various tasks.

Educational: Education of worldview concepts; cognition of the surrounding world; nurturing a sense of comradely mutual assistance, mutual understanding, a sense of responsibility, and ethics of working in pairs.

Equipment: current source, ammeter, voltmeter, ruler, key, researchable

conductors, connecting wires, computer, projector.

During the classes

I. Organizational stage. Defining Lesson Objectives. (1 min.)

II. Stage of updating basic knowledge(10 min.) – work with the whole class

1. What is current strength? What letter does it represent?

2. What formula is used to calculate current strength?

3. What is the name of the unit of measurement of current? How is it designated?

4. What is the name of the device for measuring current? How is it indicated on the diagrams?

5. What formula is used to find the electric charge passing through the cross section of a conductor if the current strength and the time of its passage are known?

6. What is electrical voltage? What letter does it represent?

7. What formula is used to calculate electrical voltage?

8. What is the unit of voltage measurement called? How is it designated?

9. What is the name of the device for measuring electrical voltage? How is it indicated on the diagrams?

10. What rules should be followed when connecting a voltmeter to a circuit?

11. What is the relationship between current and voltage?

12. What is the designation for electrical resistance?

13. How does current strength depend on resistance?

14. Formulate Ohm’s law for a section of the circuit

III . Explanation of the material. ( 10 min)

In the previous lesson, we found out that the cause of conductor resistance is the interaction of moving electrons with ions of the crystal lattice.

Different conductors have different resistance due to differences in the structure of their crystal lattice, due to different lengths and cross-sectional areas.

This means we can assume that the resistance of a conductor depends on its length and cross-sectional area, and on the substance from which it is made.

Let's conduct an experiment: The current in the circuit is measured with an ammeter, voltage with a voltmeter. Knowing these parameters and using Ohm's law, you can determine the resistance of each conductor. Various conductors are included in the current source circuit in turn:

Nickel wires of the same thickness, but different lengths;

Nickel wires of the same length, but different thicknesses (different cross-sectional areas);

Nickel and nichrome wires of the same length and thickness.

conclusions:

    Of two nickel wires of the same thickness, the longer wire has greater resistance;

    Of two nickel wires of the same length, the wire with a smaller cross-section has the greater resistance;

    Nickel and nichrome wires of the same size have different resistances.

The dependence of the resistance of a conductor on its size and the substance from which the conductor is made was studied experimentally for the first time Ohm.

He found that resistance is directly proportional to the length of the conductor, inversely proportional to its cross-sectional area and depends on its substance.

How to take into account the dependence of resistance on the material from which the conductor is made?

To do this, calculate the so-called resistivity of the substance.

Resistivity is a physical quantity that determines the resistance of a conductor made of a given substance with a length of 1 m and a cross-sectional area of ​​1 m2.

The SI unit of resistivity is 1 ohm*m, or

The conductor resistivity values ​​are given in Table 8 (p. 105 8th grade physics textbook, author A.V. Peryshkin).

It has been experimentally established that the resistivity of metals increases with increasing temperature.

Of all the metals, silver and copper have the lowest resistivity. Therefore, silver and copper are the best conductors of electricity. When wiring electrical circuits, aluminum, copper and iron wires are used.

In many cases, devices with high resistance are needed. They are made from specially created alloys - substances with high resistivity.

For example, as can be seen from Table 8, the nichrome alloy has a resistivity almost 40 times greater than aluminum.

Porcelain and ebonite have such a high resistivity that they almost do not conduct electric current at all; they are used as insulators.

IV . Fixing the material.(15 minutes.)

Students are offered a version of assignments compiled in accordance with the KIMs of the State Academy of Sciences. The tasks are discussed collectively, and tasks No. 3, 4, 6 are solved one by one at the board.

Part 1

    The conductor resistance depends on


1) 0.204 Ohm 2) 0.816 Ohm 3) 2.04 Ohm 4) 28.23 Ohm

    To smoothly change the current strength you need to use

    1. Switch 3) lever rheostat

      slider rheostat 4) ammeter

    How long do you need to take nickel wire with a cross section of 0.2 mm 2 to make a rheostat with a resistance of 20 Ohms?

1) 5 m 2) 10 m 3) 15 m 4) 20 M

Part 2

    Establish a correspondence between physical quantities and formulas for their calculation. For each position in the first column, select the corresponding position in the second and write down the selected numbers in the table under the corresponding letters

Physical quantities Formula

A) current 1)

B) voltage 2)

IN) resistance 3)

4)

5)

Application Device

A) for measuring voltage 1) rheostat

B) to measure current 2) voltmeter

3) galvanometer

4) ammeter

5)electroscope

V. Homework. P 45, 46, exercise 20 No. 2 (v)

Rheostats

A rheostat is a device that is used to regulate the current in a circuit.

The simplest rheostat is a wire with high resistivity, such as nickel or nichrome.

Types of rheostats:

Slider rheostat - another type of rheostat, in which steel wire is wound around a ceramic cylinder. The wire is covered with a thin layer of scale, which does not conduct electric current, so its turns are insulated from each other. Above the winding is a metal rod along which the slider moves.

It is pressed against the turns of the winding. From the friction of the slider on the turns, the scale layer is erased and the electric current in the circuit passes from the turns of wire to the slider, then into the rod. When the rheostat is connected to the circuit, you can move the slider, thus increasing or decreasing the resistance of the rheostat.

Liquid rheostat - represents a tank with electrolyte into which metal plates are immersed.

Wire rheostat - consists of a wire made of a material with high resistivity, stretched over a frame.

Do not exceed the current strength of the rheostat, because the rheostat winding may burn out.

We often use a rheostat in everyday life, for example, adjusting the volume of the TV and radio, increasing and decreasing the speed of driving a car.

Preview:

Development of a lesson on the topic

“Calculation of conductor resistance. Resistivity"

Physics, 8th grade.

Developed by: Belovol Lyudmila Viktorovna

Physics teacher MBOU Secondary School No. 42

Krasnodar city

Science begins as soon as they begin to measure.

Exact science is unthinkable without measure.

D.I.Mendeleev

Lesson objectives:

Educational: Create conditions that encourage self-educational activity

Students, apply their knowledge in a new situation, develop the ability to solve

Calculation tasks. Determine the dependence of the conductor resistance on its length,

The cross-sectional area and the substance from which it is made.

Developmental: Develop elements of creative search based on the technique of generalizing knowledge, the ability to analyze, observe, assemble electrical circuits, draw diagrams, develop practical work skills, interest in the subject by performing various tasks.

Educational: Education of worldview concepts; cognition of the surrounding world; nurturing a sense of comradely mutual assistance, mutual understanding, a sense of responsibility, and ethics of working in pairs.

Equipment : current source, ammeter, voltmeter, ruler, key, researchable

Conductors, connecting wires, computer, projector.

During the classes

I. Organizational stage. Defining Lesson Objectives. (1 min.)

II. Stage of updating basic knowledge(10 min.) – work with the whole class

1. What is current strength? What letter does it represent?

2. What formula is used to calculate current strength?

3. What is the name of the unit of measurement of current? How is it designated?

4. What is the name of the device for measuring current? How is it indicated on the diagrams?

5. What formula is used to find the electric charge passing through the cross section of a conductor if the current strength and the time of its passage are known?

6. What is electrical voltage? What letter does it represent?

7. What formula is used to calculate electrical voltage?

8. What is the unit of voltage measurement called? How is it designated?

9. What is the name of the device for measuring electrical voltage? How is it indicated on the diagrams?

10. What rules should be followed when connecting a voltmeter to a circuit?

11. What is the relationship between current and voltage?

12. What is the designation for electrical resistance?

13. How does current strength depend on resistance?

14. Formulate Ohm’s law for a section of the circuit

III. Explanation of the material. ( 10 min)

In the previous lesson, we found out that the cause of conductor resistanceis the interaction of moving electrons with ions of the crystal lattice.

Different conductors have different resistance due to differences in the structure of their crystal lattice, due to different lengths and cross-sectional areas.

This means we can assume that the resistance of a conductor depends on its length and cross-sectional area, and on the substance from which it is made.

Let's conduct an experiment : The current in the circuit is measured with an ammeter, voltage with a voltmeter. Knowing these parameters and using Ohm's law, you can determine the resistance of each conductor. Various conductors are included in the current source circuit in turn:

Nickel wires of the same thickness, but different lengths;

Nickel wires of the same length, but different thicknesses (different cross-sectional areas);

Nickel and nichrome wires of the same length and thickness.

Conclusions :

  1. Of two nickel wires of the same thickness, the longer wire has greater resistance;
  1. Of two nickel wires of the same length, the wire with a smaller cross-section has the greater resistance;
  1. Nickel and nichrome wires of the same size have different resistances.

The dependence of the resistance of a conductor on its size and the substance from which the conductor is made was studied experimentally for the first time Om.

He found that resistance is directly proportional to the length of the conductor, inversely proportional to its cross-sectional area and depends on its substance.

How to take into account the dependence of resistance on the material from which the conductor is made?

To do this, calculate the so-called resistivity of the substance.

Resistivityis a physical quantity that determines the resistance of a conductor made of a given substance with a length of 1 m and a cross-sectional area of ​​1 m2.

The SI unit of resistivity is 1 ohm*m, or

The conductor resistivity values ​​are given in Table 8 (p. 105 8th grade physics textbook, author A.V. Peryshkin).

It has been experimentally established that the resistivity of metals increases with increasing temperature.

Of all the metals, silver and copper have the lowest resistivity. Therefore, silver and copper are the best conductors of electricity. When wiring electrical circuits, aluminum, copper and iron wires are used.

In many cases, devices with high resistance are needed. They are made from specially created alloys - substances with high resistivity.

For example, as can be seen from Table 8, the nichrome alloy has a resistivity almost 40 times greater than aluminum.

Porcelain and ebonite have such a high resistivity that they almost do not conduct electric current at all; they are used as insulators.

IV. Fixing the material.(15 minutes.)

Students are offered a version of assignments compiled in accordance with the KIMs of the State Academy of Sciences. The tasks are discussed collectively, and tasks No. 3, 4, 6 are solved one by one at the board.

Part 1

  1. The conductor resistance depends on
  1. voltage applied to it
  2. on current and applied voltage
  3. from conductor material
  4. on the length, cross-sectional area and material of the conductor
  1. resistance of a nickel conductor with a length of 0.4 m and a cross-sectional area of ​​0.1 mm 2 equals 1 ohm
  2. resistance of a nickel conductor with a length of 1 m and a cross-sectional area of ​​1 mm 2 equals 0.4 ohm
  3. resistance of a nickel conductor with a length of 1 m and a cross-sectional area of ​​0.4 mm 2 equals 1 ohm
  4. resistance of a nickel conductor with a length of 0.1 m and a cross-sectional area of ​​0.1 mm 2 equals 0.4 ohm
  1. How will the resistance of a conductor change if its length is doubled?
  1. will increase 2 times 3) will not change
  2. will decrease by 2 times 4) will become equal to zero
  1. The copper wire has a length of 240 cm and a cross-sectional area of ​​0.2 mm 2 . Calculate the resistance of this wire.

1) 0.204 Ohm 2) 0.816 Ohm 3) 2.04 Ohm 4) 28.23 Ohm

  1. To smoothly change the current strength you need to use
  1. Switch 3) lever rheostat
  2. slider rheostat 4) ammeter
  1. What length do you need to take nickel wire with a cross section of 0.2 mm 2 for making a rheostat with a resistance of 20 Ohms?

1) 5 m 2) 10 m 3) 15 m 4) 20 M

Part 2

  1. Establish a correspondence between physical quantities and formulas for their calculation. For each position in the first column, select the corresponding position in the second and write down the selected numbers in the table under the corresponding letters

Physical quantities Formula

A) current strength 1)

B) voltage 2)

Technological lesson map

Full name of teacher: Shimonaeva E.N.

Grade: 8

UMC: “A.V. Peryshkin"

Subject: Physics

Topic: Calculation of conductor resistance. Resistivity.

Lesson type: Lesson on discovering new knowledge

Place and role of the lesson in the topic being studied: Chapter “Electrical phenomena”, lesson 11

Target: Establish the dependence of conductor resistance on length, cross-sectional area, type of substance and introduce the concept of electrical resistivity.

*Planned results

Subject knowledge, subject actions

UUD

regulatory

educational

communicative

personal

Know how to determine resistivity and use a resistivity table; apply acquired knowledge when solving problems; are able to compare and systematize experimental and theoretical knowledge; perform an experiment and know how to use instructions. We derived a formula for calculating the resistance of a conductor.

Able to carry out actions according to instructions; evaluate and adjust results; set goals for the lesson and plan your actions to achieve the goal; draw conclusions.

Able to analyze data obtained experimentally; generalize; draw conclusions.

Able to build productive interaction in a group, participate in collective discussion; listen, give reasons for your answer.

Represent the pattern of connections between natural phenomena; cognitive interest has been formed; are able to independently acquire knowledge and practical skills.

During the classes

**Name

lesson stage

The task that should be

solved (within the framework of achieving the planned lesson results)

Forms of organizing student activities

Teacher’s actions to organize students’ activities

Students’ actions (subject, cognitive,

regulatory)

The result of interaction between the teacher and students to achieve the planned lesson results

Diagnostics

achieving the planned lesson results

Motivation (self-determination for educational activities)

Development of internal readiness for educational activities. organize self-assessment in class.

Conversation

I create a problematic situation

Analyze the problem situation

Interaction on educational activities has been established

100% readiness of students for the lesson

Updating knowledge

Fixing individual difficulties.

Interrogation

(reception of thin and thick questions)

Organize and regulate student interaction

Know the definitions of current, voltage, resistance

The number of correct answers among respondents is 100%

Identifying the location and causes of the difficulty

Organizing an analysis of the current situation, identifying the location and causes of the difficulty

Frontal survey

I'm asking a question

Record the step at which the difficulty arose

Building a project to get out of a problem

Create a problematic situation

Determine the objectives of the lesson. Create a plan to get out of a problematic situation

Survey

Conversation

I create a problematic situation

I invite students to state the objectives of the lesson

Resolve a problematic situation.

State the objectives of the lesson

Formulate the definition of “Air Humidity” and write it down in your notebook.

Lesson objectives defined

The definition of “Air Humidity” has been formulated and a formula has been derived.

100% of the students surveyed expressed the objectives of the lesson and plans for solving problems.

100% of respondents

students

Implementation of a plan to overcome difficulties

Confirm theoretical data through experiment.

Enter a new physical quantity

Work individually, or in pairs, groups/pairs

Story

I organize work in a group. I control the correctness of the work

I give a definition of a new physical quantity, designation

Carry out measurements, calculations, formulate conclusions

Write down

We determined the dependence of resistance on various properties of the conductor and formulated a conclusion.

A new physical quantity has been introduced, a definition, designation, and unit of measurement have been given.

100 %

Students completed the task and formulated conclusions

Consolidation

Apply the acquired knowledge in practical problem solving

Work individually, or in pairs, groups/pairs.

I control the correctness of the work

Solve calculation problems

Correctly solved calculation problems using a new formula

100% of students solved the problems correctly

Summing up, reflection.

Summarize the knowledge gained and draw conclusions

Conversation

I summarize the students' answers.

To view downloaded projects, you must install mimio® Studio software. All project materials are packaged in .rar format archives; after downloading, they need to be unpacked, for example, using the WinRAR program.

Project type: for schoolchildren

Classes: 8th grade, 9th grade

Sections: Physics

Teacher: Popova Nadezhda Anatolyevna - physics teacher

Educational institution: MBOU Budarinskaya secondary school, Novoanninsky district, Volgograd region

Added: Sunday, 08/11/2013

Description:

Lesson topic: Calculation of conductor resistance. Resistivity

Lesson in 8th grade

Physics teacher – Nadezhda Anatolyevna Popova MBOU Budarinskaya secondary school, Novoanninsky district, Volgograd region

Target.

Educational:

  • Create conditions that encourage students’ self-educational activity, apply their knowledge in a new situation, develop skills in working with the interactive Mimio console, and the ability to solve calculations and experimental problems. Establish the dependence of the resistance of a conductor on its length, cross-sectional area and the material from which it is made.

Developmental:

  • Develop elements of creative search based on the technique of generalizing knowledge, the ability to analyze, observe, assemble electrical circuits, draw diagrams, develop practical work skills, interest in the subject by performing various tasks.

Educational: Education of worldview concepts; cognition of the surrounding world; nurturing a sense of comradely mutual assistance, mutual understanding, a sense of responsibility, and ethics of working in pairs.

Lesson structure.

1. Organizational stage.

2. Updating knowledge.

3. Solving problems on the application of Ohm's law for a section of a circuit.

4. Studying a new topic.

5. Calculation of conductor resistivity.

6. Repeating the connection of the ammeter and voltmeter

7. Practical work.

8. Summing up.

9. Homework

Equipment: Ammeter and voltmeter (demonstration), current sources, ammeters, laboratory voltmeters, test conductors, connecting wires, keys, Mimio kit

Lesson stage

Using Mimio

Teacher activities

Student activity

1. Organizational stage.

The topic of the lesson and goals are announced

Write down the topic in your notebook

2. Updating knowledge.

The teacher offers students knowledge of formulas and laws using a game situation.

1.The letters of the encrypted word were hidden under the balls. It is necessary to establish a correspondence between the physical quantity and the formula attached to the ball, burst the ball, open the letter and write it down in the table with a marker

2. Similar situation, task for checking units of measurement of physical quantities

Working with an interactive whiteboard

3. Repetition of Ohm's law for a section of the circuit.

Formulate Ohm's law for a section of a circuit.

How to calculate voltage using Ohm's law?

Resistance?

Using Ohm's law for the circuit section, fill in the table. Solving problems on the application of Ohm's law for a section of a circuit is carried out by filling out the table.

To check, we put forward hidden answers

Answer questions.

The student enters the results into a table.

4. Studying a new topic.

In the previous lesson, we found out what causes conductor resistance. Name it.

Let's find out: what does the resistance of a conductor depend on?

ESM demonstration from page 2

Page 3 Let's establish the dependence of resistance on conductor length

The current increased, but the voltage remained the same. Therefore: resistance depends on the length of the conductor.

Page 4 Let us establish the dependence on the cross-sectional area.

The current increases. We draw a conclusion. The resistance of a conductor depends on the cross-sectional area: the larger the area, the lower the resistance (and vice versa, the smaller the cross-sectional area of ​​the conductor, the greater the resistance).

Page 5 Let us establish the dependence of resistance on the type of substance.

The resistance of a conductor depends on the type of substance (material) from which it is made.

Page 6

The dependence of resistance on the geometric dimensions of the conductor (length and cross-sectional area) and the substance from which it is made was first established by Georg Ohm.

Resistance is directly proportional to the length of the conductor, inversely proportional to its cross-sectional area and depends on the substance of the conductor.

The resistance of a conductor made of a given substance with a length of 1 meter and a cross-sectional area of ​​1 square millimeter is called the resistivity of the conductor.

The SI unit of resistivity is 1 ohm*m, or

The conductor resistivity values ​​are given in Table 8 (p. 105 8th grade physics textbook, author A.V. Peryshkin)

Students:

1. The electric field of positive ions acts on electrons and reduces their speed. As a result, the current strength decreases and the resistance of the conductor increases.

2. The electric field created by electrons also affects neighboring electrons, reducing their speed, and therefore reduces the current strength, increasing the resistance of the conductor.

Write down the resistance dependences in a notebook

Pupils take turns at the blackboard working with an interactive stand

5. Solving the problem of calculating the resistivity of a conductor

Task. Determine the resistance of the telephone wire between the cities of Yuzhno-Sakhalinsk and Tomari, if the distance between them is 180 kilometers, and the wires are made of iron wire with a cross-section of 12 square millimeters.

To check the recording of the conditions, we put forward the ready-made “book”.

The answer is hidden behind the screen.

Students write down the conditions of the problem in a notebook.

The teacher invites the student to write down the solution to the problem with a marker.

6. Repeating the connection of the ammeter and voltmeter

Let us repeat how an ammeter and a voltmeter are connected in a circuit. Look at the diagrams and find which diagram has the error.

We repeat how to determine the price of dividing devices.

The student selects the correct drawing and the answer is automatically checked.

The measurement results of the instruments are recorded in a notebook.

7. Practical work

If you have a document camera and not enough equipment for the class, you can conduct practical work on a demonstration table by projecting the experience onto the board.

Guys, on your tables you have instruments: an ammeter, a voltmeter, a conductor in the form of a spiral, connecting wires, a current source. The conductor is made of iron, the cross-sectional area is 1 square millimeter.

How can you determine the length of a conductor?

As a result of the discussion, we come to the conclusion:

1) Stretch the conductor and measure its length. Then, so that the conductor takes the shape of a spiral, wind it around a pencil.

2) Using an ammeter and voltmeter, measure the current and voltage on the conductor and calculate its resistance. Then, using resistivity and cross-sectional area, calculate the length of the conductor

Students perform practical work in the second way..

The teacher checks the results of the work.

8. Reflection. (Summarizing.)

Match questions and answers, pulling them to the right place.

As a result, we get a rainbow, which itself speaks of a favorable outcome of the lesson. Evaluations for the work are announced.

Working with the board

9. Homework:

P. 45, 46, exercise 20 No. 2 (a), 4.

Record tasks in a diary