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:

1. Assemble a chain consisting of power supply, key, two spirals, rheostat, ammeter, connected in series. The rheostat engine is located approximately in the middle.
2. 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.
3. 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.
4. 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. , IN
Voltage U, V
Resistance R 1, Ohm
Resistance R 2, Ohm
Resistance R 1,2, Ohm
Resistance R p. , Ohm

1. Using a rheostat, change the resistance of the circuit and repeat the measurements again, writing down the results in the table (experiment No. 2).
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.
3. Calculate the sum of the voltages U 1.2 + U p. And compare with the voltage U. Make a conclusion.
4. 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:

1. 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.
2. Assemble a circuit consisting of a power supply, a key, an ammeter and two coils connected in parallel.
3. 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.
4. After being checked by the teacher, close the circuit.
5. 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.
6. Measure the currents I 1 and I 2 in each coil. Enter the data into the table:

1. 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).
2. Calculate the sum of the currents I 1 + I 2 on both spirals and compare with the current strength I. Draw a conclusion.
3. Calculate the sum of the conductivities γ 1 + γ 2 and compare with the conductivity γ. Make a conclusion.

1. 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:

1. Weigh the inner beaker of the calorimeter.
2. 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.
3. 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.
4. Measure the initial water temperature in the calorimeter.
5. After checking the circuit by the teacher, close it, noticing the moment of its turning on.
6. Measure the current passing through the heater and the voltage at its terminals.
7. Calculate the power supplied by the electric heater.
8. 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.
9. Calculate the useful Q - the amount of heat received by the water and the calorimeter.
10. Calculate Q total, - the amount of heat released by the electric heater for the measured period of time.
11. 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 magnetic field coils with current. Assembling the electromagnet and testing its action.

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:

1. 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.
2. 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.
3. Use a rheostat to change the current in the circuit and observe the action of the electromagnet on the arrow. Make a conclusion.
4. Assemble the arched magnet from the finished parts. Connect the magnet coils in series so that opposite magnetic poles are formed at their free ends. Check the poles with a compass. Determine with the help of the compass where the north and where is the south pole of the magnet.
5. 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.
6. List the known applications of electromagnets in your report.
7. 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:

1. Place a piece of paper on top of a foam pad.
2. Place a plane-parallel glass plate on a sheet of paper and trace its outlines with a pencil.
3. 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.
4. Move pin 3 until it is in line with the imaginary images of pins 1 and 2 in the glass plate (see figure a)).
5. 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.

1. 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.

.

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.
2. 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.
3. sin a = sin g = n st. =
4. Thus, by measuring AC and AB, the relative refractive index of the glass can be calculated.
5. 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 determines its magnetic effect.

Tasks.

Educational:

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

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

3.Create the organizational conditions for the experiment to determine the dependence magnetic properties at a conductor with 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 contribute to 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.

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 in question in the story from the book "Electricity in its applications" by Dari. 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 lift 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 in the least 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 use the compass to locate 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 strength of the current passing 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.

Subject: Assembling the electromagnet and testing its action.

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

Equipment:

• current source (battery or accumulator);
• rheostat;
• key;
• connecting wires;
• compass;
• parts for assembling an electromagnet.

Directions for work

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

2. 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.

3. Change the current in the circuit with a rheostat and observe the action of the electromagnet on the arrow. Make a conclusion.

4. Assemble the arc magnet from the finished parts. Connect the coils of the electromagnet in series with yourself 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.

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 determines its magnetic effect.

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 replacement 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 contribute to 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. ABOUT 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.

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 lift 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 in the least 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 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.

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.

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. 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.

Equipment: power supply, rheostat, key, connecting wires, compass (magnetic needle), arc-shaped magnet, ammeter, ruler, parts for assembling an electromagnet (coil and core).
Safety regulations. Read the rules carefully and sign that you agree to follow them .

Caution! Electricity! Make sure that the insulation of the conductors is intact. When conducting experiments with magnetic fields, take off the watch and remove the mobile phone.

I have read the rules, I undertake to comply. ________________________

Student signature

Progress.

1. 
   Make up the electrical, coil, rheostat, ammeter and key by connecting them in series. Draw a diagram of the circuit assembly.

Electrical circuit assembly diagram

1. 
   Close the circuit and use the magnetic arrow to locate the poles at the coil.

Record the measurement results in Table 1.

16

1. 
   Move the magnetic needle along the axis of the coil this distanceL2 ,

Table 1

4. Insert the iron core into the coil and observe the action

electromagnet on the arrow. Measure the distanceL3 from coil to arrow and

amperageI3 in a spool with a core. Record the measurement results in

Table 2.

1. 
   Move the magnetic needle along the axis of the cored coil to such a distance.

arrow slightly. Measure this distance and amperageI4 in the coil.

Also record the measurement results in table 2.

table 2

1. 
   Compare the results obtained in point 3 and point 4. Makeoutput: ______________

1. 
   Change the current in the circuit with the help of a rheostat and observe the action

____________________________________________________________________

____________________________________________________________________

1. 
   Assemble the arched magnet from the finished parts. Electromagnet coils

17

CONTROL QUESTIONS:

What are the similarities between a current coil with a magnetic needle? __________ ________________________________________________________________________________________________________________________________________

1. 
   Why is the magnetic effect of the coil, through which the current flows, increased if an iron core is introduced into it? _______________________________________ ____________________________________________________________________________________________________________________________________________________________________________________________________________

1. 
   What is called an electromagnet? For what purposes are electromagnets used (3-5 examples)? ______________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ________

1. 
   Is it possible to connect the coils of a horseshoe electromagnet so that the ends of the coil have the same poles? ________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

1. 
   What pole will appear at the pointed end of an iron nail if the south pole of the magnet is brought closer to its head? Explain the phenomenon ___________ ____________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________