Laboratory work 9 assembly of an electromagnet. Outline of the lesson "The magnetic field of a coil with a current

Plan - a summary of a physics lesson in grade 8 on the topic:

“Magnetic field of a coil with current. Electromagnets.

Laboratory work No. 8 "Assembling an electromagnet and testing its operation."

Lesson objectives: teach how to assemble an electromagnet from finished parts and experimentally check what it depends on magnetic action.

Tasks.

Educational:

1. using a game form of activity in the lesson, repeat the basic concepts of the topic: magnetic field, its features, sources, graphic representation.

2. to organize activities in pairs of permanent and replaceable composition for the assembly of an electromagnet.

3. to create organizational conditions for conducting an experiment to determine the dependence of the magnetic properties of a conductor with a current.

Developing:

1. to develop students' skills of effective thinking: the ability to highlight the main thing in the studied material, the ability to compare the studied facts and processes, the ability to logically express their thoughts.

2. to develop skills in working with physical equipment.

3. to develop the emotional-volitional sphere of students, when solving problems of varying degrees of complexity.

Educational:

1. to create conditions for the formation of such qualities as respect, independence and patience.

2. to promote the formation of a positive "I - competence".

Cognitive. Allocate and formulate a cognitive goal. Build logical chains of reasoning.

Regulatory. They pose a learning task based on the correlation of what has already been learned and what is still unknown.

Communicative. Exchange knowledge between team members to make effective joint decisions.

Lesson type: methodological lesson.

Problem-based learning technology and CSR.

Laboratory equipment: collapsible electromagnet with parts (designed for frontal laboratory work on electricity and magnetism), current source, rheostat, key, connecting wires, compass.

Demonstrations:

The structure and course of the lesson.

	Lesson stage	Stage objectives	Activity teachers	Activity pupil		Time
Motivational - indicative component
	Organizational stage	Psychological preparation for communication	Provides a supportive attitude.	Get ready to work.	Personal

	The stage of motivation and actualization (determination of the topic of the lesson and the joint goal of the activity).	Provide activities to update knowledge and define the goals of the lesson.	Invites you to play a game and review the basic concepts of the topic. Suggests to discuss the positional problem and name the topic of the lesson, determine the goal.	They are trying to answer, to solve a positional problem. Determine the topic of the lesson and the purpose.

Operational and executive component
	Learning new material.	Promote the activities of students in independent decision tasks.	Offers to organize activities according to the proposed tasks.	Perform laboratory work. They work individually, in pairs. Class work.	Personal, cognitive, regulatory
Reflexive - evaluative component
	Control and self-examination of knowledge.	Reveal the quality of the assimilation of the material.	Offers to solve problems.	Decide. They answer. They are discussing.	Personal, cognitive, regulatory
	Summing up, reflection.	Adequate self-esteem of the individual, their capabilities and abilities, merits and limitations is formed.	He offers to answer the questions of the questionnaire “It's time to draw conclusions”.	They answer.	Personal, cognitive, regulatory
	Submitting homework.	Consolidation of the studied material.	Writing on the board.	They write it down in a diary.	Personal

1. Review the basic concepts of the topic. Entrance testing.

The game "Continue the sentence".

Substances that attract iron objects are called ... (magnets).

Interaction of a conductor with current and a magnetic needle
first discovered by a Danish scientist ... (Oersted).

Interaction forces arise between conductors with current, which are called ... (magnetic).

The places of the magnet, in which the magnetic action is most pronounced, are called ... (magnet poles).

There is ...
(a magnetic field).

Source magnetic field serves ... (moving charge).

7. Lines along which the axes are located in a magnetic field
small magnetic arrows are called ... (magnetic lines of force).

A magnetic field around a conductor with a current can be detected, for example, ... (using a magnetic needle or using iron filings).

9. Bodies that retain their magnetization for a long time are called ... (permanent magnets).

10. The like poles of a magnet ..., and unlike - ... (repel,

are attracted

2. "Black box".

What's hidden in the drawer? You will find out if you understand what is discussed in the story from Dari's book "Electricity in Its Applications". A performance by a French magician in Algeria.

“On the stage is a small bound box with a handle on the lid. I call a stronger person out of the audience. In response to my challenge, an Arab of medium height, but strong build ...

“Come to the courts,” I said, “and raise the box. The Arab bent down, lifted the box and asked arrogantly:

- Nothing more?

- Wait a little, - I answered.

Then, assuming a serious air, I made an imperious gesture and said in a solemn tone:

- You are now weaker than a woman. Try to lift the box again.

The strongman was not at all afraid of my charms, he again took up the box, but this time the box resists and, despite the desperate efforts of the Arab, remains motionless, as if chained to a place. The Arab is trying to lift the box with enough force to lift a huge weight, but all in vain. Tired, out of breath and burning with shame, he finally stops. Now he begins to believe in the power of sorcery. "

(From the book by Ya.I. Perelman "Entertaining physics. Part 2".)

Question. What is the secret of sorcery?

They are discussing. Express their position. From the "Black Box" I take out a coil, iron filings and a galvanic cell.

Demonstrations:

1) the action of a solenoid (coil without a core), through which a direct current flows, on a magnetic needle;

2) the action of a solenoid (coil with a core), through which a direct current flows, on the armature;

3) the attraction of iron filings by a coil with a core.

They conclude what an electromagnet is and formulate the purpose and objectives of the lesson.

3. Implementation of laboratory work.

A coil with an iron core inside is called electromagnet. An electromagnet is one of the main parts of many technical devices. I suggest you assemble an electromagnet and determine what its magnetic action will depend on.

Laboratory work No. 8

"Assembling an electromagnet and testing its operation"

Purpose of work: to assemble an electromagnet from ready-made parts and experimentally check what its magnetic action depends on.

Directions for work

Task number 1. Make an electrical circuit from a battery, coil, key, connecting everything in series. Close the circuit and with using a compass determine the magnetic poles at the coil. Move the compass along the axis of the coil to such a distance at which the effect of the magnetic field of the coil on the compass needle is insignificant. Insert the iron core into the coil and observe the action of the electromagnet on the arrow. Make a conclusion.

Task number 2. Take two coils with an iron core, but with a different number of turns. Check the poles with a compass. Determine the action of the electromagnets on the arrow. Compare and draw a conclusion.

Task No. 3. Insert the iron core into the coil and observe the action of the electromagnet on the arrow. Use a rheostat to change the current in the circuit and observe the action of the electromagnet on the arrow. Make a conclusion.

They work in static pairs.

1 row - task number 1; 2nd row - task number 2; 3 row - task number 3. Exchange tasks.

1 row - task number 3; 2nd row - task number 1; 3 row - task number 2.Exchange tasks.

1 row - task number 2; 2nd row - task number 3; 3rd row - task number 1.Exchange tasks.

Work in pairs of replacement composition.

At the end of the experiments,conclusions:

1. If an electric current passes through the coil, then the coil becomes a magnet;

2.the magnetic action of the coil can be enhanced or weakened:
changing the number of turns of the coil;

3.changing the current flowing through the coil;

4. by inserting an iron or steel core inside the coil.

Sheet myself training, myself rebuttals and myself ovaluation.

1. Entrance testing.The game "Continue the sentence".

1.__________________________

2.__________________________

3.__________________________

4.__________________________

5.__________________________

6.__________________________

7.__________________________

8.__________________________

9.__________________________

10._________________________

2. Laboratory work No. 8 "Assembling an electromagnet and testing its operation"

Purpose of the work: to collect _______________ from finished parts and check by experience what the _____________ action depends on.

Devices and materials: galvanic cell, rheostat, key, connecting wires, compass, parts for assembling an electromagnet.

Progress.

Task number 1.

Task number 2.

Task number 3.

Statement	I completely agree	I partially agree	Partially disagree	Strongly disagree
I have acquired a lot of new information on the topic of the lesson
I felt comfortable
The information obtained in the lesson will be useful to me in the future.
I received answers to all my questions on the topic of the lesson.
I will definitely share this information with my friends.

Purpose of work: to assemble an electromagnet from ready-made parts and experimentally check what its magnetic action depends on.

To test the electromagnet, we will assemble a circuit, the diagram of which is shown in Figure 97 of the textbook.

An example of a job.

( north) pole.

2.When the iron core is inserted into the coil, the effect of the magnetic field on the compass needle is increased.

3.With an increase in the current in the coil, its magnetic effect on the compass needle increases, and, conversely, when it decreases, it decreases.

4. Determination of the poles of an arched magnet is the same as in point 1.

Measurement of voltage in various sections of the electrical circuit.

Determination of the resistance of the conductor using an ammeter and a voltmeter.

purpose of work: learn how to measure the voltage and resistance of a section of the circuit.

Devices and materials: power supply, spiral resistors (2 pcs.), ammeter and voltmeter, rheostat, key, connecting wires.

Directions for work:

Assemble a circuit consisting of a power supply, a key, two coils, a rheostat, an ammeter, connected in series. The rheostat engine is located approximately in the middle.
Draw a diagram of the circuit you assembled and show on it where the voltmeter is connected when measuring the voltage on each spiral and on two spirals together.
Measure the current in the circuit I, the voltages U 1, U 2 at the ends of each spiral and the voltage U 1,2 in the section of the circuit consisting of two spirals.
Measure the voltage across the rheostat U p. and at the poles of the current source U. Enter the data in the table (experiment No. 1):

Experience number	№1	№2
Current I, A
Voltage U 1, V
Voltage U 2, V
Voltage U 1.2 V
Voltage U p. , V
Voltage U, V
Resistance R 1, Ohm
Resistance R 2, Ohm
Resistance R 1,2, Ohm
Resistance R p. , Ohm

Using a rheostat, change the resistance of the circuit and repeat the measurements again, writing down the results in the table (experiment no. 2).
Calculate the sum of the voltages U 1 + U 2 on both spirals and compare with the voltage U 1.2. Make a conclusion.
Calculate the sum of the voltages U 1.2 + U p. And compare with the voltage U. Make a conclusion.
From each individual measurement, calculate the resistances R 1, R 2, R 1,2 and R p. ... Draw conclusions.

Laboratory work No. 10

Checking the laws of parallel connection of resistors.

purpose of work: check the laws of parallel connection of resistors (for currents and resistances). Remember and write down these laws.

Devices and materials: power supply, spiral resistors (2 pcs.), ammeter and voltmeter, key, connecting wires.

Directions for work:

Take a close look at what is indicated on the panel of the voltmeter and ammeter. Determine the limits of measurements, the price of divisions. Find the instrumental errors of these devices from the table. Write down the data in a notebook.
Assemble a circuit consisting of a power supply, a key, an ammeter and two coils connected in parallel.
Draw a diagram of the circuit you assembled and show on it where the voltmeter is connected when measuring the voltage at the poles of the current source and on the two spirals together, as well as how to connect the ammeter to measure the current in each of the resistors.
After being checked by the teacher, close the circuit.
Measure the current in the circuit I, the voltage U at the poles of the current source and the voltage U 1,2 in the section of the circuit consisting of two spirals.
Measure the currents I 1 and I 2 in each coil. Enter the data in the table:

Calculate the resistances R 1 and R 2, as well as the conductivity γ 1 and γ 2, of each spiral, the resistance R and the conductivity γ 1,2 of the section of two parallel-connected spirals. (Conductivity is called the reciprocal of resistance: γ = 1 / R Ohm -1).
Calculate the sum of the currents I 1 + I 2 on both spirals and compare with the current strength I. Draw a conclusion.
Calculate the sum of the conductivities γ 1 + γ 2 and compare with the conductivity γ. Make a conclusion.

Estimate the errors of direct and indirect measurements.

Laboratory work No. 11

Determination of power and efficiency of an electric heater.

Devices and materials:

Clock, laboratory power supply, laboratory electric heater, ammeter, voltmeter, key, connecting wires, calorimeter, thermometer, scales, beaker, vessel with water.

Directions for work:

Weigh the inner beaker of the calorimeter.
Pour 150-180 ml of water into the calorimeter and lower the electric heater coil into it. The water should completely cover the coil. Calculate the mass of water poured into the calorimeter.
Assemble an electrical circuit consisting of a power source, a key, an electric heater (located in the calorimeter) and an ammeter, connected in series. Connect a voltmeter to measure the voltage on the electric heater. Depict schematic diagram this chain.
Measure the initial water temperature in the calorimeter.
After checking the circuit by the teacher, close it, noticing the moment of its turning on.
Measure the current passing through the heater and the voltage at its terminals.
Calculate the power supplied by the electric heater.
After 15 - 20 minutes after the start of heating (note this moment in time), measure the water temperature in the calorimeter again. At the same time, do not touch the coil of the electric heater with the thermometer. Switch off the chain.
Calculate the useful Q - the amount of heat received by the water and the calorimeter.
Calculate Q total, - the amount of heat released by the electric heater for the measured period of time.
Calculate the efficiency of a laboratory electric heating installation.

Use the tabular data from the textbook "Physics. 8th grade." edited by A.V. Peryshkina.

Laboratory work No. 12

Study of the magnetic field of the coil with current. Assembling the electromagnet and testing its operation.

C spruce work: 1. investigate the magnetic field of the coil with current using the magnetic arrow, determine the magnetic poles of this coil; 2. Assemble an electromagnet from finished parts and test its magnetic action experimentally.

Devices and materials: laboratory power supply, rheostat, key, ammeter, connecting wires, compass, parts for assembling an electromagnet, various metal objects (nails, coins, buttons, etc.).

Directions for work:

Make an electrical circuit from a power source, coil, rheostat and key, connecting everything in series. Close the circuit and use the compass to locate the magnetic poles at the coil. Make a schematic drawing of the experiment, indicating on it the electric and magnetic poles of the coil, and depicting the appearance of its magnetic lines.
Move the compass along the axis of the coil to such a distance that the effect of the coil's magnetic field on the compass needle is negligible. Insert the steel core into the coil and observe the action of the electromagnet on the arrow. Make a conclusion.
Use a rheostat to change the current in the circuit and observe the action of the electromagnet on the arrow. Make a conclusion.
Assemble the arched magnet from the finished parts. Connect the magnet coils in series with each other so that opposite magnetic poles are obtained at their free ends. Check the poles with a compass. Determine with the help of a compass where the north and where is the south pole of the magnet.
Using the obtained electromagnet, determine which of the bodies offered to you are attracted to it, and which are not. Write the result in a notebook.
List the known applications of electromagnets in your report.
Draw a conclusion from the work done.

Laboratory work No. 13

Determination of the refractive index of glass

Purpose of work:

Determine the refractive index of a trapezoidal glass plate.

Devices and materials:

Trapezoidal glass plate with plane-parallel edges, 4 sewing pins, protractor, square, pencil, sheet of paper, foam lining.

Directions for work:

Place a piece of paper on top of a foam pad.
Place a plane-parallel glass plate on a sheet of paper and trace its outlines with a pencil.
Lift the foam pad and, without moving the plate, stick pins 1 and 2 into the sheet of paper. In this case, you need to look at the pins through the glass and stick pin 2 so that pin 1 is not visible behind it.
Move pin 3 until it is in line with the imaginary images of pins 1 and 2 in the glass plate (see figure a)).
Draw a straight line through points 1 and 2. Draw a straight line through point 3, parallel to straight line 12 (Fig. B)). Connect points O 1 and O 2 (Fig. C)).

6. Draw a perpendicular to the air-glass interface at point O 1. Specify the angle of incidence α and the angle of refraction γ

7. Measure the angle of incidence α and the angle of refraction γ using

Protractor. Record the measurement data.

Use a calculator or Bradis tables to find sin a and sin g ... Determine the refractive index of glass n st.-carriage. relative to air, assuming the absolute refractive index of air n air.@ 1.

You can define n st.-cart. and in another way, using fig d). To do this, it is necessary to extend the perpendicular to the air-glass interface as far down as possible and mark on it an arbitrary point A. Then, continue the incident and refracted rays with dotted lines.
Drop from point A the perpendiculars to these extensions - AB and AC. L AO 1 C = a, l AO 1 B = g ... Triangles AO 1 B and AO 1 C are rectangular and have the same hypotenuse O 1 A.
sin a = sin g = n st. =
Thus, by measuring AC and AB, the relative refractive index of the glass can be calculated.
Estimate the error of the measurements made.

Plan - a summary of a physics lesson in grade 8 on the topic:

“Magnetic field of a coil with current. Electromagnets.

Laboratory work No. 8 "Assembling an electromagnet and testing its operation."

Lesson objectives: teach how to assemble an electromagnet from finished parts and experimentally check what its magnetic action depends on.

Tasks.

Educational:

1. using a game form of activity in the lesson, repeat the basic concepts of the topic: magnetic field, its features, sources, graphic representation.

2. to organize activities in pairs of permanent and replaceable composition for the assembly of an electromagnet.

3. to create organizational conditions for conducting an experiment to determine the dependence of the magnetic properties of a conductor with a current.

Developing:

2. to develop skills in working with physical equipment.

3. to develop the emotional-volitional sphere of students, when solving problems of varying degrees of complexity.

Educational:

1. to create conditions for the formation of such qualities as respect, independence and patience.

2. to promote the formation of a positive "I - competence".

Cognitive. Allocate and formulate a cognitive goal. Build logical chains of reasoning.

Regulatory. They pose a learning task based on the correlation of what has already been learned and what is still unknown.

Communicative. Exchange knowledge between team members to make effective joint decisions.

Personal. O a conscious, respectful and benevolent attitude towards another person, his opinion.

Lesson type: methodological lesson.

Problem-based learning technology and CSR.

Laboratory equipment: collapsible electromagnet with parts (designed for frontal laboratory work on electricity and magnetism), current source, rheostat, key, connecting wires, compass.

Demonstrations:

The structure and course of the lesson.

	Lesson stage	Stage objectives	Activity teachers	Activity pupil		Time
Motivational - indicative component
	Organizational stage	Psychological preparation for communication	Provides a supportive attitude.	Get ready to work.	Personal

	The stage of motivation and actualization (determination of the topic of the lesson and the joint goal of the activity).	Provide activities to update knowledge and define the goals of the lesson.	Invites you to play a game and review the basic concepts of the topic. Suggests to discuss the positional problem and name the topic of the lesson, determine the goal.	They are trying to answer, to solve a positional problem. Determine the topic of the lesson and the purpose.

Operational and executive component
	Learning new material.	Facilitate the activities of students in independent problem solving.	Offers to organize activities according to the proposed tasks.	Perform laboratory work. They work individually, in pairs. Class work.	Personal, cognitive, regulatory
Reflexive - evaluative component
	Control and self-examination of knowledge.	Reveal the quality of the assimilation of the material.	Offers to solve problems.	Decide. They answer. They are discussing.	Personal, cognitive, regulatory
	Summing up, reflection.	Adequate self-esteem of the individual, their capabilities and abilities, merits and limitations is formed.	He offers to answer the questions of the questionnaire “It's time to draw conclusions”.	They answer.	Personal, cognitive, regulatory
	Submitting homework.	Consolidation of the studied material.	Writing on the board.	They write it down in a diary.	Personal

1. Review the basic concepts of the topic. Entrance testing.

The game "Continue the sentence".

Substances that attract iron objects are called ... (magnets).

Interaction of a conductor with current and a magnetic needle
first discovered by a Danish scientist ... (Oersted).

Interaction forces arise between conductors with current, which are called ... (magnetic).

The places of the magnet, in which the magnetic action is most pronounced, are called ... (magnet poles).

There is ...
(a magnetic field).

The source of the magnetic field is ... (moving charge).

7. Lines along which the axes are located in a magnetic field
small magnetic arrows are called ... (magnetic lines of force).

A magnetic field around a conductor with a current can be detected, for example, ... (using a magnetic needle or using iron filings).

9. Bodies that retain their magnetization for a long time are called ... (permanent magnets).

10. The like poles of a magnet ..., and unlike - ... (repel,

are attracted

2. "Black box".

What's hidden in the drawer? You will find out if you understand what is discussed in the story from Dari's book "Electricity in Its Applications". A performance by a French magician in Algeria.

“On the stage is a small bound box with a handle on the lid. I call a stronger person out of the audience. In response to my challenge, an Arab of medium height, but strong build ...

“Come to the courts,” I said, “and raise the box. The Arab bent down, lifted the box and asked arrogantly:

- Nothing more?

- Wait a little, - I answered.

Then, assuming a serious air, I made an imperious gesture and said in a solemn tone:

- You are now weaker than a woman. Try to lift the box again.

(From the book by Ya.I. Perelman "Entertaining physics. Part 2".)

Question. What is the secret of sorcery?

They are discussing. Express their position. From the "Black Box" I take out a coil, iron filings and a galvanic cell.

Demonstrations:

1) the action of a solenoid (coil without a core), through which a direct current flows, on a magnetic needle;

2) the action of a solenoid (coil with a core), through which a direct current flows, on the armature;

3) the attraction of iron filings by a coil with a core.

They conclude what an electromagnet is and formulate the purpose and objectives of the lesson.

3. Implementation of laboratory work.

Laboratory work No. 8

"Assembling an electromagnet and testing its operation"

Purpose of work: to assemble an electromagnet from ready-made parts and experimentally check what its magnetic action depends on.

Directions for work

Task number 1. Make an electrical circuit from a battery, coil, key, connecting everything in series. Close the circuit and use the compass to locate the magnetic poles at the coil. Move the compass along the axis of the coil to such a distance that the effect of the coil's magnetic field on the compass needle is negligible. Insert the iron core into the coil and observe the action of the electromagnet on the arrow. Make a conclusion.

They work in static pairs.

1st row - task number 1; 2nd row - task number 2; 3 row - task number 3.

Work in pairs of replacement composition.

1st row - task number 3; 2nd row - task number 1; 3 row - task number 2.

1st row - task number 2; 2nd row - task number 3; 3rd row - task number 1.

At the end of the experiments, conclusions:

1. If an electric current passes through the coil, then the coil becomes a magnet;

2.the magnetic action of the coil can be enhanced or weakened:
a. by changing the number of turns of the coil;

b. changing the strength of the current passing through the coil;

c. by introducing an iron or steel core inside the coil.

Self-study sheet, self-assessment.

1. Entrance testing. The game "Continue the sentence".

1.__________________________

2.__________________________

3.__________________________

4.__________________________

5.__________________________

6.__________________________

7.__________________________

8.__________________________

9.__________________________

10._________________________

2. Laboratory work No. 8 "Assembling an electromagnet and testing its operation"

Purpose of the work: to collect _______________ from finished parts and check by experience what the _____________ action depends on.

Devices and materials: galvanic cell, rheostat, key, connecting wires, compass, parts for assembling an electromagnet.

Progress.

Task number 1.

Task number 2.

Task number 3.

Statement	I completely agree	I partially agree	Partially disagree	Strongly disagree
I have acquired a lot of new information on the topic of the lesson
I felt comfortable
The information obtained in the lesson will be useful to me in the future.
I received answers to all my questions on the topic of the lesson.
I will definitely share this information with my friends.

MOU "Kremenovskaya secondary school"

Plan - a summary of a physics lesson in grade 8 on the topic:

“Magnetic field of a coil with current. Electromagnets and their application. "

Teacher: Savostikov S.V.

Plan - a summary of a physics lesson in grade 8 on the topic:

“Magnetic field of a coil with current. Electromagnets and their application. "

Lesson objectives:

- educational: to study ways to enhance and weaken the magnetic field of a coil with a current; teach to determine the magnetic poles of the coil with current; consider the principle of operation of an electromagnet and its field of application; teach how to collect an electromagnet from
finished parts and empirically check what determines its magnetic effect;

Developing: develop the ability to generalize knowledge, apply
knowledge in specific situations; develop skills to work with the device
mi; develop cognitive interest in the subject;

Educational: education of perseverance, hard work, accuracy in the implementation of practical work.

Lesson type: combined (using ICT).

Lesson equipment: computers, author's presentation "Electromagnets".

Laboratory equipment: collapsible electromagnet with parts (designed for frontal laboratory work on electricity and magnetism), current source, rheostat, key, connecting wires, compass.

Demonstrations:

1) the action of the conductor through which the constant flows

current, per magnetic needle;

2) the action of a solenoid (coil without a core), through which a direct current flows, on a magnetic needle;

the attraction of iron filings by a nail on which
a wire connected to a constant source
current.

Strokelesson

I. Organizing time.

Announcement of the topic of the lesson.

NS. Updating basic knowledge(6 min).

"Continue the offer"

Substances that attract iron objects are called ... (with magnets).

Interaction of a conductor with current and a magnetic needle
first discovered by a Danish scientist ... (Oersted).

Interaction forces arise between conductors with current, which are called ... (magnetic).

The places of the magnet, in which the magnetic action is most pronounced, are called ... (by the poles of a magnet).

There is ...
(a magnetic field).

The source of the magnetic field is ... (moving charge).

7. Lines along which the axes are located in a magnetic field
small magnetic arrows, called ... (power magicianthread lines).

A magnetic field around a current carrying conductor can be detected, for example ... (using the magnetic arrow or withusing iron filings).

If the magnet is broken in half, then the first piece and the second
a piece of magnet have poles ... (northern -Nand southern -S).

11.Bodies that retain their magnetization for a long time are called ... (permanent magnets).

12. Like poles of a magnet ..., and unlike poles - ... (repel, attract).

III... Main part. Learning new material (20 min).

Slides number 1-2

Frontal poll

Why can be used to study the magnetic field
iron filings? (In a magnetic field, the sawdust is magnetized and becomes magnetic arrows)

What is called the magnetic line of a magnetic field? (The lines along which the axes of the small magnetic arrows are located in the magnetic field)

Why is the concept of a magnetic field line introduced? (With the help of magnetic lines it is convenient to depict magnetic fields graphically)

How to show experimentally that the direction of magnetic lines
related to the direction of the current? (When the direction of the current in the conductor changes, all magnetic arrows turn 180 O )

Slide No. З

What unites these drawings (see slide) and how are they different?

Slide number 4

Can you make a magnet that only has a North Pole? But only the South Pole? (Impossible to domagnet, which would be missing one of the poles).

If you break a magnet in two, will those parts be magnets? (If you break a magnet apart, then all of itparts will be magnets).

What substances can be magnetized? (Iron, cobalt,nickel, alloys of these elements).

Slide number 5

Refrigerator magnets have become so popular that they are collectible. So at the moment, the record for the number of collected magnets belongs to Louise Greenfarb (USA). At the moment, a record of 35,000 magnets is registered in the Guinness Book of Records.

Slide number 6

- Can iron nail, steel screwdriver, aluminum wire, copper coil, steel bolt be magnetized? (Iron nail, steel bolt and steel screwdriver can bemagnet, but the aluminum wire and copper coil onit is impossible to magnetise, but if an electric current is sent through them, thenthey will create a magnetic field.)

Explain the experience in the pictures (see slide).

Slide number 7

Electromagnet

André Marie Ampere, conducting experiments with a coil (solenoid), showed the equivalence of its magnetic field to the field of a permanent magnet Solenoid(from the Greek solen - a tube and eidos - a kind) - a wire spiral through which an electric current is passed to create a magnetic field.

Studies of the magnetic field of a circular current led Ampere to the idea that permanent magnetism is explained by the existence of elementary circular currents flowing around the particles that make up the magnets.

Teacher: Magnetism is one of the manifestations of electricity. How to create a magnetic field inside the coil? Can this field be changed?

Slides number 8-10

Demonstrations by the teacher:

the action of the conductor through which the constant flows
current, per magnetic needle;

the action of a solenoid (coil without a core), through which a direct current flows, on a magnetic needle;

the action of a solenoid (coil with a core), along which
a direct current flows through the magnetic needle;

the attraction of iron filings by a nail on which a wire is wound, connected to a direct current source.

Teacher: The coil consists of a large number of turns of wire wound on wooden frame... When there is current in the coil, the iron filings are attracted to its ends; when the current is turned off, they fall off.

We will include a rheostat in the circuit containing the coil and with the help of it we will change the current in the coil. With an increase in the current strength, the effect of the magnetic field of the coil with current increases, with a decrease, it weakens.

The magnetic effect of a coil with a current can be significantly enhanced without changing the number of its turns and the strength of the current in it. To do this, you need to insert an iron rod (core) inside the coil. Iron | introduced into the coil increases its magnetic effect.

A coil with an iron core inside is called electromagnet. An electromagnet is one of the main parts of many technical devices.

At the end of the experiments, conclusions are drawn:

if an electric current passes through the coil, then the coil
becomes a magnet;

the magnetic action of the coil can be increased or decreased:
changing the number of turns of the coil;

changing the strength of the current passing through the coil;

by introducing an iron or steel core inside the coil.

Slide number 11

Teacher: The windings of electromagnets are made from insulated aluminum or copper wire, although there are also superconducting electromagnets. Magnetic cores are made of soft magnetic materials - usually from electrical or high-quality structural steel, cast steel and cast iron, iron-nickel and iron-cobalt alloys.

An electromagnet is a device whose magnetic field is created only when an electric current flows.

Slide number 12

Think and answer

Can a wire wound on a nail be called an electromagnet? (Yes.)

What determines the magnetic properties of an electromagnet? (From
current strength, from the number of turns, from magnetic properties core, on the shape and size of the coil.)

3. A current was sent through the electromagnet, and then it was reduced by
twice. How have the magnetic properties of an electromagnet changed? (Decreased by 2 times.)

Slides number 13-15

1ststudent: William Sterzhen (1783-1850) - English electrical engineer, created the first horseshoe-shaped electromagnet capable of holding a load greater than its own weight (a 200-gram electromagnet was able to hold 4 kg of iron).

The electromagnet, demonstrated by Sterzhen on May 23, 1825, looked like a horseshoe bent, varnished, iron rod 30 cm long and 1.3 cm in diameter, covered on top with one layer of insulated copper wire. The electromagnet weighed 3600 g and was significantly stronger than natural magnets of the same mass.

Joule, experimenting with the very first magnet of Sterzhen, managed to bring its lifting force to 20 kg. This was in the same 1825.

Joseph Henry (1797-1878) - American physicist, improved the electromagnet.

In 1827, J. Henry began to insulate not the core, but the wire itself. Only then did it become possible to wind the turns in several layers. J. Henry investigated various methods of winding a wire to obtain an electromagnet. He created a magnet of 29 kg, holding a gigantic weight at that time - 936 kg.

Slides number 16-18

2ndstudent: The factories use electromagnetic cranes that can carry huge loads without attachments. How do they do it?

An arc-shaped electromagnet holds an anchor (iron plate) with a suspended load. Rectangular electromagnets are designed to grip and hold sheets, rails and other long loads during transportation.

As long as there is current in the winding of the electromagnet, not a single piece of iron will fall. But if the current in the winding is interrupted for some reason, an accident is inevitable. And there have been such cases.

In one American plant, an electromagnet lifted iron blanks.

Suddenly, at the Niagara Falls power station, which supplies current, something happened, the current in the winding of the electromagnet disappeared; a mass of metal fell off the electromagnet and fell with all its weight on the worker's head.

In order to avoid the repetition of such accidents, as well as in order to save the consumption of electrical energy, special devices began to be arranged with electromagnets: after the objects to be carried were lifted by a magnet, strong steel supports are lowered and tightly closed from the side, which then themselves support the load, the current during transportation is interrupted.

Electromagnetic traverses are used to move long loads.

Probably the most powerful circular lifting electromagnets are used in seaports for reloading scrap metal. Their weight reaches 10 tons, the carrying capacity is up to 64 tons, and the breakout force is up to 128 tons.

Slides number 19-22

3rd student: Basically, the field of application of electromagnets is electrical machines and devices included in industrial automation systems, in equipment for the protection of electrical installations. Useful properties of electromagnets:

demagnetized quickly when the current is turned off,

it is possible to manufacture electromagnets of any size,

during operation, you can adjust the magnetic action by changing the current in the circuit.

Electromagnets are used in lifting devices, for cleaning coal from metal, for sorting different types of seeds, for forming iron parts, in tape recorders.

Electromagnets are widely used in technology due to their remarkable properties.

Single-phase alternating current electromagnets are designed for remote control of actuators for various industrial and domestic purposes. Electromagnets with high lifting force are used in factories to carry steel or cast iron products, as well as steel and cast iron shavings, ingots.

Electromagnets are used in telegraph, telephone, electric bell, electric motor, transformer, electromagnetic relay and many other devices.

As part of various mechanisms, electromagnets are used as a drive to implement the necessary translational movement (rotation) of the working bodies of machines or to create a holding force. These are electromagnets of lifting machines, electromagnets of clutches and brakes, electromagnets used in various starters, contactors, switches, electrical measuring instruments, and so on.

Slide number 23

4th student: Brian Tveits, CEO of Walker Magnetics, is proud to present the world's largest pendant electromagnet. Its weight (88 tons) is about 22 tons more than the current winner of the Guinness Book of Records from the United States. Its carrying capacity is approximately 270 tons.

The world's largest electromagnet is used in Switzerland. The 8-sided electromagnet consists of a core made of 6400 tons of mild steel and an aluminum coil weighing 1100 tons. The coil consists of 168 turns electrically welded to the frame. A current of 30 thousand A, passing through the coil, creates a magnetic field with a power of 5 kilogauss. The dimensions of the electromagnet, exceeding the height of a 4-storey building, are 12x12x12 m, and the total weight is 7810 tons. It took more metal to make it than to build the Eiffel Tower.

The world's heaviest magnet has a diameter of 60 m and weighs 36 thousand tons. It was made for the 10 TeV synchrophasotron installed at the Joint Institute nuclear research in Dubna, Moscow region.

Demonstration: Electromagnetic Telegraph.

Fastening (4 min).

3 people on computers perform work "Reshalkin" on the topic "Electromagnet" from the site
Slide number 24

What is called an electromagnet? (Iron core coil)

What methods can be used to enhance the magnetic effect of the coil with

electric shock? (the magnetic effect of the coil can be enhanced:
changing the number of turns of the coil, changing the strength of the current passing through the coil, by introducing an iron or steel core inside the coil.)

In which direction is the current coil installed,
suspended from long thin conductors? What a similarity
does it have a magnetic needle?

4. For what purposes are electromagnets used in factories?

Practical part (12 min).

Slide number 25

Laboratory work.

Pupils' performance of laboratory work No. 8 on their own "Assembling an electromagnet and testing its action ”, page 175 of the textbook“ Physics-8 ”(by A3. Peryshkin,“ Bustard ”, 2009).

Sla ydy No. 25-26

Summing up and grading.

Vi. Homework.

2. To carry out a home research project "Motor for
minutes " (instructions are given to each student for work
at home, see Appendix).

Motor in 10 minutes project

It is always interesting to observe changing phenomena, especially if you yourself participate in the creation of these phenomena. Now we will assemble the simplest (but really working) electric motor, consisting of a power source, a magnet and a small coil of wire, which we will also make ourselves. There is a secret that will make this set of objects become an electric motor; a secret that is both clever and amazingly simple. Here's what we need:

1.5 V battery or rechargeable battery;

holder with contacts for the battery;

1 meter of wire with enamel insulation (diameter 0.8-1 mm);

0.3 meters of bare wire (diameter 0.8-1 mm).

We'll start by winding the coil, the part of the electric motor that will rotate. To make the coil sufficiently flat and round, we wind it on a suitable cylindrical frame, such as an AA battery.

Leaving 5 cm of wires free from each end, we wind 15-20 turns on a cylindrical frame. Do not try to wind the coil very tightly and evenly, a small degree of freedom will help the coil to better maintain its shape.

Now carefully remove the coil from the frame, trying to maintain the resulting shape.

Then wrap the loose ends of the wire several times around the loops to maintain shape, making sure that the new bonding loops are exactly opposite each other.

The coil should look like this:

Now is the time for the secret, the feature that will make the motor work. This is a sophisticated and non-obvious trick, and very difficult to detect when the motor is running. Even people who know a lot about engine operation may be surprised to discover this secret.

Keeping the spool upright, place one of the free ends of the spool on the edge of the table. Using a sharp knife, remove the top half of the insulation from one free end of the spool (holder), leaving the bottom half intact. Do the same for the other end of the coil, making sure that the bare ends of the wire point up at the two free ends of the coil.

What is the meaning of this technique? The coil will rest on two holders made of bare wire. These holders will be attached to different ends of the battery so that electrical current can flow from one holder through the coil to the other holder. But this will only happen when the bare halves of the wire are lowered down, touching the holders.

Now you need to make a support for the coil. it
just the coils of wire that support the coil and allow it to spin. They are made from bare wire, so
how, in addition to supporting the coil, they must deliver electric current to it. Just wrap every piece of non-insulated pro
water around a small nail - get the part you want
engine.

The base of our first motor is a battery holder. This will also be a suitable base because with the battery installed it will be heavy enough to keep the motor from shaking. Put the five pieces together as shown in the picture (without the magnet at first). Place a magnet on top of the battery and gently push the coil ...

If done correctly, the coil will start spinning rapidly!

Hope it works for you the first time. If the motor still does not start, carefully check all electrical connections. Does the coil spin freely? Is the magnet close enough? If not enough, install additional magnets or trim the wire holders.

When the motor starts up, the only thing you need to pay attention to is not to overheat the battery, since the current is large enough. Just remove the coil and the chain will be broken.

Show your motor model to your classmates and teacher in the next physics lesson. Let the comments of classmates and the teacher's assessment of your project become an incentive for further successful design of physical devices and knowledge of the world around you. Wish you success!

Laboratory work No. 8

"Assembling an electromagnet and testing its operation"

Purpose of work: assemble an electromagnet from finished parts and test by experience what its magnetic action depends on.

Devices and materials: a battery of three cells (or accumulators), a rheostat, a key, connecting wires, a compass, parts for assembling an electromagnet.

Directions for work

1. Make an electrical circuit from the battery, coil, rheostat and key, connecting everything in series. Close the circuit and use the compass to locate the magnetic poles at the coil.

Move the compass along the axis of the coil to such a distance that the effect of the coil's magnetic field on the compass needle is negligible. Insert the iron core into the coil and observe the action of the electromagnet on the arrow. Make a conclusion.

Use a rheostat to change the current in the circuit and observe the action of the electromagnet on the arrow. Make a conclusion.

Assemble the arched magnet from the finished parts. Connect the coils of the electromagnet with each other in series so that opposite magnetic poles are obtained at their free ends. Check the poles with a compass. Determine with the help of a compass where the north and where is the south pole of the magnet.

History of the electromagnetic telegraph

V In the world, the electromagnetic telegraph was invented by the Russian scientist and diplomat Pavel Lvovich Schilling in 1832. While on a business trip in China and other countries, he acutely felt the need for a high-speed means of communication. In a telegraph apparatus, he used the property of a magnetic needle to deviate in one direction or another, depending on the direction of the current passing through the wire.

Schilling's apparatus consisted of two parts: a transmitter and a receiver. Two telegraphs were connected by conductors to each other and to an electric battery. The transmitter had 16 keys. If you pressed the white keys, the current went in one direction, if the black keys, in the other. These current pulses were reached through the wires of the receiver, which had six coils; near each spool, two magnetic arrows and a small disk were hung on a thread (see left figure). One side of the disc was painted with black paint, the other with white.

Depending on the direction of the current in the coils, the magnetic arrows turned in one direction or the other, and the telegrapher receiving the signal saw black or white circles. If the current did not flow into the coil, then the disc was visible with an edge. Schilling developed an alphabet for his apparatus. Schilling's devices operated on the world's first telegraph line, built by the inventor in St. Petersburg in 1832, between the Winter Palace and the offices of some ministers.

In 1837, the American Samuel Morse designed a telegraph apparatus that records signals (see right figure). In 1844, the first telegraph line, equipped with Morse apparatus, was opened between Washington and Baltimore.

Morse's electromagnetic telegraph and the system for recording signals in the form of dots and dashes developed by him have become widespread. However, the Morse apparatus had serious drawbacks: the transmitted telegram must be deciphered and then recorded; low transmission speed.

NS The world's first direct-printing apparatus was invented in 1850 by the Russian scientist Boris Semenovich Yakobi. This machine had a printing wheel that rotated at the same speed as the wheel of another machine installed at a nearby station (see lower figure). The rims of both wheels were engraved with letters, numbers and signs that were wetted with paint. Electromagnets were placed under the wheels of the apparatus, and paper strips were pulled between the anchors of the electromagnets and the wheels.

For example, you need to transmit the letter "A". When the letter A was located at the bottom on both wheels, a key was pressed on one of the devices and the chain was closed. The anchors of the electromagnets were attracted to the cores and pressed paper strips to the wheels of both devices. The letter A was simultaneously imprinted on the tapes. To transmit any other letter, it is necessary to "catch" the moment when the desired letter will be on the wheels of both devices below, and press the key.

What are the necessary conditions for correct transmission in the Jacobi apparatus? First, the wheels must rotate at the same speed; second - on the wheels of both vehicles, the same letters must occupy the same positions in space at any time. These principles have also been used in the latest telegraphs.

Many inventors worked on the improvement of telegraph communication. There were telegraphs that transmitted and received tens of thousands of words per hour, but they are complex and cumbersome. Teletypes - direct-printing telegraph devices with a keyboard like a typewriter - have become widespread in their time. Currently, telegraphs are not used, they were supplanted by telephone, cellular and Internet communications.

Explanatory note

... №6 on subject current Magnetic field. Magnetic field direct current. Magnetic lines. 1 55 Magnetic field coils with current. Electromagnets and their at...

Physics program for grades 7-9 of educational institutions Authors of the program: E. M. Gutnik, A. V. Peryshkin M .: Bustard. 2007 textbooks (included in the Federal List)

Program

... №6 on subject"The work and power of the electric current»1 Electromagnetic phenomena. (6 h) 54 Magnetic field. Magnetic field direct current. Magnetic lines. 1 55 Magnetic field coils with current. Electromagnets and their at...

Order No. from “” 201 Physics work program for the basic level of physics study in basic school grade 8

Working programm

... physics... Diagnostics on repeated material 7 class... Diagnostic work Section 1. ELECTROMAGNETIC PHENOMENA Theme ... magnetic fields coils with current on the number of turns, on the strength current v reel, from the presence of a core; application electromagnets ...

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