Laboratory work measurement of current strength. Assembling an electrical circuit and measuring the current strength in its various sections. half the division of the measuring instrument

Item: physics

Class 9A ( hearing impaired children)

Teacher: Kishchenko Lidia Mikhailovna

Subject: Current measurement. Laboratory work No. 3 "Assembly electrical circuit and measuring the strength of the current in its various sections.

Target: Formation of electrical circuit assembly skills; consolidation of skills in determining the division price, the measurement limit of the ammeter, its correct inclusion in the circuit and use to measure the current strength.

Tasks: 1) Find out how you can measure the current strength; 2) learn how to correctly include an ammeter in an electrical circuit and measure the current strength with it; 3) perform laboratory work on assembling an electrical circuit and measuring the current strength in its various sections.

Lesson type : Combined lesson.

Teaching methods: Visual, practical, inductive, laboratory work, frontal survey.

Form of organization learning activities students: group, individual.

Equipment: power supply, low-voltage lamp, key, ammeter, connecting wires; textbook, computer, projector.

Planned results:

Learn how to assemble an electrical circuit, use an ammeter to determine the current strength in an electrical circuit, draw diagrams of electrical circuits; be able to perform experiments, analyze and evaluate the results of the experiment.

Lesson stage	Teacher activity	Student activities
1. Org. Moment	Greeting, checking the emotional state of students (strong link)	Welcome teachers	Regulatory: volitional self-regulation Personal: the action of meaning formation Communicative: planning educational cooperation with the teacher and peers
2. Phonetic charging. Duty sound: p	We speak correctly. Write: Ammeter Series	say the words Behind the screen: Electrical circuit	Regulatory: control, correction of correct pronunciation
3. Create motivation. Determining the topic of the lesson	Ask questions: Why do I need an ammeter? What will we do in class? What do you think the topic of our lesson is? After writing the topic, message of lesson tasks	Preparation for the perception of the material, the performance of work. Exit on the topic of the lesson by students. Write down in notebooks the number, the topic of the lesson	Regulatory: understand, accept and preserve learning task; Cognitive: search and selection necessary information, Communicative: express your thoughts and actions in speech, participate in a collective discussion of issues
4.Intelligent workout Individual work	Let's repeat the material that will help us remember what we learned in the previous lessons. 1. What is the name of the device for measuring current strength? 2. How to distinguish an ammeter from other devices? 3. Determine: 1. measurement limit 2. current value (presentation)	Answer questions	Personal: the ability to consciously build speech utterances, learning skills to determine the CD Cognitive: establishing cause-and-effect relationships, building a logical chain of reasoning Communicative: the ability to express one's thoughts with sufficient completeness, possession of monologue speech
5. New theme.	Explain how to use an ammeter 1) Included in the circuit in series. 2) Switching on is done via two terminals "+" and "-". 3) The terminal with the "+" sign is connected to the "+" of the source, the terminal "-" to the "-". 4) Protect the device from shock, shaking and dust. Textbook work page 89 fig. 61: what is shown in the pic? Preparing for LR: Look at the ammeters on your desks. The terminal with the (+) sign must always be connected to the wire coming from the (+) pole of the source. Brief conclusions on the topic of the lesson: ammeter - a device that is connected to the circuit ... in series. The ammeter shows the value ... of the current. The principle of operation of any ammeter is based on .... action of electric current. (magnetic). Is it possible to include an ammeter in a circuit with a current strength exceeding its maximum value?	Write down in a notebook: the ammeter is included in the circuit in series. Answer questions Participate in conversation Phrase by ear: Ammeter connected in series	Personal: educational and cognitive interest in new material; Regulatory: understand, accept and maintain the learning task, determine the sequence of actions, guided by the learned rules and instructions of the teacher; Cognitive: to be aware of the general method of action for solving a learning problem, apply it to solve specific problems Communicative: to express your thoughts and actions in speech, to participate in joint activities
6. Checking homework.	Check notes in notebooks	Open notebooks, show LR	personal: about awareness by students of what has already been learned, awareness of the quality and level of assimilation
7. Performing laboratory work No. 3 "Assembling an electrical circuit and measuring the current strength in its various sections."	Open notebooks for lab. work, write down: number, progress of work. 1. draw email diagrams. chains according to fig. 155 a-c. Let's check it on the board. 2. Assembly email. circuits according to scheme No. 1. Arrange the elements of the chain on the working field according to the scheme, assemble the chain. Close the key and read the ammeter. Write down. 3. Conduct experiments according to schemes No. 2 and No. 3 and write down the measurement results in a notebook. 4. Compare I1, I2, I3 and write down the output.	Work with the textbook and prepare a report. Draw diagrams in a notebook. Perform practical work. Define and write in a notebook. Carry out the task. They work in small groups. Perform a comparison and analyze the result. Write down the conclusion, hand over notebooks for verification	Personal: cognitive interest in extracting information presented in a symbolic form; Regulatory: understand, accept and maintain the learning task, determine the sequence of actions, guided by the learned rules and instructions of the teacher, exercise self-control and mutual control; Cognitive: analysis of objects in order to highlight features, selection of bases and criteria for comparison Communicative: participate in a collective discussion of issues, provide necessary assistance in cooperation, follow the rules speech behavior
8.Homework. P. 38, ex. 15(1-3).

ELECTRICITY IS AROUND, THE PLANT AND THE HOUSE IS FULL OF THEM, CHARGES EVERYWHERE: THERE AND HERE, IN ANY ATOM "LIVE". AND IF THEY SUDDENLY RUNN, THEN IMMEDIATELY CREATE CURRENTS, THE CURRENTS ARE VERY HELPING US, LIFE IS MADE FACILITATELY EASIER! IT IS AMAZING, FOR THE BENEFIT OF US, ALL THE WIRES OF "MAJESTY" ARE CALLED "ELECTRICITY!"

: Continue the sentences: Current source, receivers, closing devices connected by wires make up ... In order for there to be current in the circuit, it must be ... Drawings that show how electrical devices are connected in a circuit are called ...

I=q/t, where I is the current strength, q is the electric charge, t is the time. For the first time, the definition of current strength was given by Andre-Marie Ampère () - a French scientist, physicist and mathematician.

IN Everyday life we are surrounded by electrical appliances, we use them, therefore it is necessary to know what the current strength in the electrical circuit should be in order for the devices to work normally. We must know what maximum current we can apply to this or that wire, otherwise it will either melt or burn . Also take into account the current strength in the production of electrical installation and electrical repair work.

When included in a circuit, an ammeter, like any measuring device, should not affect the measured value; when it is included in a circuit, the current strength in it almost does not change. Ammeters are used with different divisions (determine the divisions of the ammeter). What is the maximum current it can handle? It is impossible to exceed the current strength, otherwise the device will be damaged.

Before starting the task, let's repeat the safety rules when working with electrical appliances: 1. Be careful and disciplined, follow the instructions of the teacher exactly. 2. Do not start work without the teacher's permission. 3. When conducting experiments, do not allow the limiting loads of measuring instruments. 4. When assembling the electrical circuit, avoid crossing wires. 5. Turn on the assembled circuit only after checking and with the permission of the teacher. 6.After finishing work, turn off the power supply, then disassemble the electrical circuit.

Homework Design task: Make a draft of the electrical circuit for lighting the room. The circuit must ensure that the following conditions are met: three lamps with separate switching on give light to the room, when one lamp burns out or turns off, the rest do not go out, there is an automatic disconnection of the circuit from the current source in case of a short circuit; current source - galvanic cell.

When working with electrical appliances, safety precautions must be strictly and unswervingly observed, otherwise your life will be endangered. Current strength at 50 Hz Effect of current 0-0.5 mA Absent 0.5-2 mA Loss of sensation 2-10 mA Pain, muscle contractions mA Increasing effect on muscles, some damage Respiratory paralysis 100 mA-3 A urgent resuscitation required More than 3 AO cardiac arrest. Severe burns. (If the shock was brief, then the heart can be resuscitated)

"Guess the words" REMAP (unit of physical quantity) LUNOK (unit of physical quantity) ROSOLTIA (a body that is made of a dielectric) SLEKERPOOKT (physical device) NORTKELE (a particle with the smallest charge in nature)

Grigorieva Elena Alekseevna

02.01.2016

Lesson topic

Ammeter. Current measurement. Laboratory work number 4.

Target

Familiarization of students with a device for measuring current strength - an ammeter; formation of electrical circuit assembly skills; skills in determining the division value, the measurement limit of the ammeter, its correct inclusion in the circuit and use to measure the current strength.

Tasks

1) Find out how you can measure the current strength; 2) learn how to correctly include an ammeter in an electrical circuit and measure the current strength with it; 3) perform laboratory work on assembling an electrical circuit and measuring the current strength in its various sections.

Lesson type Combined lesson.

Lesson Form

Traditional lesson with research elements.

Teaching methods

Visual, practical, inductive, laboratory work, frontal survey.

Form of organization of educational activities of students

Group, frontal.

Equipment

Power supply, low-voltage lamp on a stand, key, ammeter, connecting wires; textbook, computer, projector, demonstration ammeter.

Planned results

1) At the level of memorization: name the elements of the electrical circuit, ammeter; reproduce definitions electricity, current strength. 2) At the level of understanding: understand how to connect an ammeter to an electrical circuit. 3) At the level of application in typical situations: assemble an electrical circuit, use an ammeter to determine the current strength in an electrical circuit, draw diagrams of electrical circuits; be able to perform experiments, analyze and evaluate the results of the experiment.

Lesson steps:

3 Repetition of material

4 new material

1 Organizational moment: greeting, checking the emotional state of students.

(2 minutes)

Hello guys! Our today's lesson will be held under the motto: "And apple trees will bloom on Mars"! I would like you to be attentive, correct and friendly, as you will need to work in pairs.

Slide 1. Greetings.

2 Homework. Paragraph 38, ex. 25.

(3 min)

Paragraph 38, ex. 25.

Slide 2. Homework.

3 Repetition of material

(5 minutes)

Let's repeat the material that will help you and I remember what activates your brain activity.

Slide 3. Current strength. Control

Check with each other how well you did the job and draw a smiley corresponding to your assessment.

4 New material

(10 min)

Today we will get acquainted with an electrical measuring device that allows you to measure the current strength in an electrical circuit - an ammeter.

Slide 4. Ammeters

An ammeter is a device for measuring current in a circuit. Its device and principle of operation are similar to a galvanometer. Its work is based on the magnetic action of the current. Let's determine the division value, the measurement limit of the ammeters shown in the figures.

Slide 5. Inclusion of an ammeter in the circuit and its designation on the diagram

Rules for using an ammeter. 1) Included in the circuit in series. 2) Switching on is done via two terminals "+" and "-". 3) The terminal with the "+" sign is connected to the "+" of the source, "-" to the "-". 4) Protect the device from shock, shaking and dust.

Slide 6. Current measurement

Let's assemble a virtual electrical circuit and measure the current strength.

Slide 7. Current measurement

Let's make the necessary entries in the virtual notebook.

5 Performing laboratory work No. 4 "Assembling an electrical circuit and measuring the current strength in its various sections."

(20 minutes)

Now we proceed directly to the implementation of laboratory work No. 4 according to the description in the textbook, p. 224.

WITH
layd 8. textbook_225

Slide 9. textbook_226

Sources used

Textbook "Physics. Grade 8" Peryshkin A. V. M. "Bud" 2014.

1. What do the “+” and “-” signs near the terminals of the device mean?

These signs indicate the poles of the current source to which the device must be connected.

2. What is the maximum current strength it can measure?

3. What is the value of division of its scale?

What is the smallest current that can be measured with this instrument?

$C = 0.05 A$; $I_(min) = \frac(0.05)(2) = 0.025 A$.

2. Assembling an electrical circuit and measuring the current in it.

1. Assemble the electrical circuit according to the drawing. Check the assembly with the teacher! Close the chain.

2. Draw a circuit diagram and indicate the direction of the current in the circuit with a solid arrow, and the direction of movement of charge carriers with a dotted arrow.

3. Reverse the direction of the current in the circuit. Check the circuit with the teacher! Write how you did it and whether changing the direction of the current affected the strength of the current and the glow of the light bulb.

Swapped the wires on the current source and ammeter. The current strength has not changed.

4. Measure and enter in the table the values of the current flowing between the “+” terminal of the current source and the key (section 1); the strength of the current flowing between the key and the light bulb (section 3); current I4 flowing between the light bulb and the “-” terminal of the current source (section 4). Draw conclusions about the value of the current in various parts of the circuit.

$I_1 = 0.5A$;
$I_2 = 0.5 A$;
$I_3 = 0.5 A$;
$I_4 = 1.25 A$.

5. Draw circuit diagrams for measuring currents $I_3$ and $I_4$.

Scheme 2 and Scheme 3

6. Replace the light bulb in the last circuit, first with a resistor on the socket, then with a resistor on the holders. Measure and enter in the table the values of the currents in them $I_4"$ and $I_4"$.

7. Compare the currents $I_4$, $I_3"$ and $I_4"$ and draw conclusions.

$I_1 = I_2 = I_3$;
$I_3< I_4$.

Turning on the ammeter at various points in the circuit does not change the current strength, and replacing the light bulb with a resistor changes the current strength.

3. Answers to security questions/

1. Why is the current strength in different parts of the circuit the same?

Because current flows in different parts of the circuit in the same time.

2. Will the exclusion from the ammeter circuit affect the light bulb? Why?

No, it won't. Because the ammeter has a small resistance and practically does not consume electricity.