Topic: Assembling the electromagnet and testing its operation.

Objective: assemble an electromagnet from ready-made parts and test its magnetic effect by experience.

Equipment:

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

Instructions 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 determine the magnetic poles of the coil.

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

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

4. Assemble the arc magnet from the prefabricated parts. Connect the coils of the electromagnet to each other in series so that on them loose ends obtained opposite magnetic poles. Check the poles with a compass. Use a compass to determine where the north and where is the south pole of the magnet.

Measurement of voltage in various parts of the electrical circuit.

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

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

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

Instructions for work:

1. Assemble a circuit consisting of a power source, a key, two spirals, a rheostat, an ammeter connected in series. The rheostat engine is located approximately in the middle.
2. Draw a diagram of the circuit you have 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 at the rheostat U p. and on 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, recording the results in a 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 your own conclusions.

Lab #10

Checking the laws of parallel connection of resistors.

Objective: 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.

Instructions for work:

1. Carefully consider what is indicated on the panel of the voltmeter and ammeter. Determine the limits of measurements, the price of divisions. Use the table to find the instrumental errors of these instruments. Write down the data in a notebook.
2. Assemble a circuit consisting of a power source, a key, an ammeter and two spirals connected in parallel.
3. Draw a diagram of the circuit you have 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 checking 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 spiral. Enter the data in 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 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 conductance γ. Make a conclusion.

1. Evaluate direct and indirect measurement errors.

Lab #11

Determination of the power and efficiency of the electric heater.

Devices and materials:

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

Instructions for work:

1. Weigh the inner beaker of the calorimeter.
2. Pour 150-180 ml of water into the calorimeter and lower the coil of the electric heater 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 voltage across the electric heater. Draw a schematic diagram of this circuit.
4. Measure the initial temperature of the water in the calorimeter.
5. After checking the circuit by the teacher, close it, noting the moment in time it was turned on.
6. Measure the current through the heater and the voltage at its terminals.
7. Calculate the power generated by the electric heater.
8. After 15 - 20 minutes after the start of heating (note this point in time), measure the water temperature in the calorimeter again. At the same time, it is impossible to touch the electric heater spiral with a thermometer. Turn off the circuit.
9. Calculate useful Q - the amount of heat received by 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. Peryshkin.

Lab #12

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

C spruce work: 1. explore the magnetic field of the coil with current using a magnetic needle, determine the magnetic poles of this coil; 2. assemble an electromagnet from ready-made parts and test its magnetic effect by experience.

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

Instructions for work:

1. Make an electrical circuit from a power source, a coil, a rheostat and a key, connecting everything in series. Close the circuit and use the compass to determine the magnetic poles of the coil. Complete schematic drawing experience, 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 a distance at which the effect of the magnetic field of the coil 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 the rheostat to change the current in the circuit and observe the effect of the electromagnet on the arrow. Make a conclusion.
4. Assemble the arcuate magnet from prefabricated parts. Connect the magnet coils in series so that opposite magnetic poles are obtained at their free ends. Check the poles with a compass. Use a compass to determine where the north and where is the south pole of the magnet.
5. Using the resulting electromagnet, determine which of the bodies proposed to you are attracted to it, and which are not. Write down the result in a notebook.
6. In the report, list the applications of electromagnets known to you.
7. Make a conclusion from the work done.

Lab #13

Determination of the refractive index of glass

Objective:

Determine the refractive index of a glass plate shaped like a trapezoid.

Devices and materials:

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

Instructions for work:

1. Lay a sheet of paper on the foam pad.
2. Place a plane-parallel glass plate on a sheet of paper and trace its contours with a pencil.
3. Lift up 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 Fig. a)).
5. Draw a straight line through points 1 and 2. Draw a straight line through point 3 parallel to line 12 (Fig. b)). Connect the 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. Write down the measurement data.

1. Use a calculator or Bradis tables to find sin a and sing . Determine the refractive index of glass n Art. relative to air, considering the absolute refractive index of air n woz.@ 1.

.

1. You can determine n Art. and in another way, using Fig. d). To do this, it is necessary to continue the perpendicular to the air-glass interface as far down as possible and mark an arbitrary point A on it. Then continue the incident and refracted rays with dashed lines.
2. Drop from point A the perpendiculars to these extensions - AB and AC.Ð AO 1 C = a , Ð 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 \u003d sin g \u003d n st. =
4. Thus, by measuring AC and AB, one can calculate the relative refractive index of glass.
5. Estimate the error of the measurements made.

The purpose of the work: to assemble an electromagnet from finished parts and to test by experience 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.

1. To determine the magnetic poles of a coil with current, we bring the compass to it with the north (south) pole. north) pole. The poles of the coil thus determined are shown in the figure.

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

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

4. The determination of the poles of the arcuate magnet occurs in the same way as in paragraph 1.

Laboratory work № 8 _____________________

date of

Assembling the electromagnet and testing its operation.

Target: assemble an electromagnet from ready-made parts and test by experience what its magnetic effect depends on.

Equipment: power supply, rheostat, key, connecting wires, compass (magnetic needle), arcuate magnet, ammeter, ruler, parts for assembling an electromagnet (coil and core).

Safety rules.Read the rules carefully and sign that you agree to follow them..

Carefully! Electricity! Make sure that the insulation of the conductors is not broken. When conducting experiments with magnetic fields, you should take off your watch and put away your mobile phone.

I have read the rules and agree to abide by them. ________________________

Student Signature

Working process.

1. Make up an electrical circuit from a power source, a coil, a rheostat, an ammeter and a key, connecting them in series. Draw a circuit assembly diagram.

1. Close the circuit and use the magnetic needle to determine the poles of the coil.

Measure the distance from the coil to the needle L 1 and current I 1 in the coil.

Record the measurement results in table 1.

1. Move the magnetic needle along the axis of the coil to such a distance L2,

on which the effect of the magnetic field of the coil on the magnetic needle is negligible. Measure this distance and current I 2 in a coil. Also record the measurement results in Table 1.

Table 1

Coil without core	L 1 cm	I 1, A	L 2 cm	I 2, A

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

Electromagnet on the arrow. measure distance L 3 from the coil to the arrow and

Current strength I 3 in a core coil. Record the measurement results in

Table 2.

1. Move the magnetic needle along the axis of the core coil to

Distance L 4 , on which the action of the magnetic field of the coil on the magnetic

Arrow slightly. Measure this distance and current I 4 in the coil.

Also record the measurement results in table 2.

table 2

Coil core	L 3 cm	I 3, A	L 4 cm	I 4, A

1. Compare the results obtained in paragraph 3 and paragraph 4. Do output: ______________

____________________________________________________________________

1. Use a rheostat to change the current in the circuit and observe the effect

Electromagnet on the arrow. Do output: _____________________________

____________________________________________________________________

____________________________________________________________________

1. Assemble the arcuate magnet from prefabricated parts. Electromagnet coils

connect together in series so that opposite magnetic poles are obtained at their free ends. Check the poles with a compass, determine where the north and where is the south pole of the electromagnet. Sketch the magnetic field of the electromagnet you received.

TEST QUESTIONS:

1. What is the similarity between a coil with current and a magnetic needle? __________ ________________________________________________________________________________________________________________________________

1. Why does the magnetic effect of a coil carrying current increase if an iron core is introduced into it? ___________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________

1. What is 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 a magnet is brought near its head? Explain the phenomenon ___________ __________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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Target: To acquaint students with the device of electromagnets and their application.To encourage students to overcome difficulties in the process of mental activity, to cultivate interest in physics.

Equipment for laboratory work: power supply, rheostat, key, connecting wires, compass, electromagnet assembly parts.

Demos:device and principle of operation of an electromagnet; the use of electromagnets in an electric bell, electromagnetic: relay, telegraph.

During the classes

I. Organizing time

II. Repetition.

Checking homework

IN At the beginning of the lesson, you can conduct a short frontal survey: -. What magnetic phenomena do you know?

- What is the relationship between electric current and magnetic field?

- What particles or bodies are affected by an electric field? Will the magnetic needle deviate if it is placed near a beam of moving particles: a) electrons; b) atoms; c) positive ions?

- What is a magnetic field line called?

A straight insulated wire is laid on the floor of the laboratory under a layer of linoleum. How to determine the location of the wire and the direction of the current in it without opening the linoleum? Next, you can analyze the questions that arose when solving homework problems.

The device and principle of operation of an electromagnet

A coil carrying an electric current is magnet and has two poles - north and south. As the current increases, the magnetic field of the coil increases.

It is possible to strengthen the magnetic field of the coil in another way: it is enough to introduce an iron core inside the coil. Saying that such a coil can be called electromagnet, the teacher explains to the students that an electromagnet is one of the main parts of many technical devices: a bell, a telegraph, a telephone, a microphone, an electromagnetic relay, and others

III. Laboratory work

After a brief introduction to electromagnets and their applications, to performing laboratory work No. 9. The work is performed according to the instructions of the textbook.

In the course of laboratory work, it is necessary to draw students' attention to how, knowing the direction of the current in the turns of the coil, determine the poles of the coil (electromagnet): if you mentally “grasp” the coil with your right hand from current, placing four fingers in the direction of the current, then the bent thumb will indicate the north pole of the coil (the direction of the magnetic field lines inside the coil).

Homework

1. § 58 textbook; questions for the paragraph.

2. Do exercise 28 (p. 136).