Laws of serial and parallel connection of presentation conductors. Serial and parallel connection of conductors. Laws of serial connection of conductors

Reiteration

Chizhova Vera Alexandrovna

Physics and Computer Science Teacher

MBOU SOSH p. Krasnoe,

Nenets Autonomous Okrug.


  • The speed of the charge moving along the conductor
  • Charge passing through the conductor in 1 s
  • Denoted by ()
  • Unit of measurement (A) ampere
  • Measured with an ammeter
  • Depends on voltage and resistance (Ohm's Law)

  • Voltage is the work of an electric field to move a unit charge (1C) along a conductor
  • Indicated by a letter (U)
  • Measured with a voltmeter
  • Unit of measure (V) volts

  • The property of a conductor to impede the movement of charged particles along a conductor under the influence of an electric field
  • Denoted by R
  • Measurement unit (Ohm)
  • Depends on the physical properties of the conductor

Laws of serial connection of conductors

  • The current strength is the same in all parts of the circuit
  • The total resistance of the circuit is equal to the sum of the resistances of the individual sections of the circuit
  • The total stress is equal to the sum of the stresses in individual sections

  • 1) It is required to make a Christmas tree garland of light bulbs. designed for a voltage of 6 V so that it can be connected to a 120 V network. How many bulbs should I take for this?
  • A) 4. B) 8 C) 16 D) 20 E) 30.
  • 2) Determine the total resistance of the circuit, if the resistance of the lead wires is 2 Ohm, the included part of the rheostat
  • 64 Ohm and 294 Ohm lamps (Fig. 159).
  • 1.240 ohm; 2.180 Ohm; 3.100 ohm; 4.120 Ohm; 5.360 Ohm.
  • 3) When measuring the voltage on the conductor R 1, it turned out to be 12 V. When the voltmeter was connected to the conductor R 2 , then he showed 45 V (Fig. 160). Calculate the resistance R 2 if R 1 \u003d 40 ohms.
  • A) 360 Ohm; B) 135 Ohm; B) 150 Ohm; D) 4 Ohm; E) 40 ohms.
  • 4) In each of the two heating elements of the boiler, the current is 5 A. Determine the current in the supply wires if the elements are connected in series.
  • A) 25 A; B) 5 A; B) 10 A; D) 2.5 A.
  • 5) Conductors with a resistance of 2.4 and 6 ohms are connected in series and included in a network with a voltage of 36 V. Calculate the current in the conductors.
  • A) 3 A; B) 0.33 A; B) 432 A; D) 0.5 A; E) 0.3 A.

  • 1) Current in the conductor R 1 equal to 4 A. What is the current in the conductor R 2 (fig. 161).
  • A) 4 A; B) 2 A; B) 8 A; D) 16 A.
  • 2) Resistance of the lamp R 1 \u003d 300 Ohm, and the voltage across it is 90 V. What will the voltmeter show if it is connected to a lamp with resistance R2 \u003d 400 Ohm (Fig. 162)?
  • A) 240 V; B) 180 V; B) 100 V; D) 120 V; E) 360 V.
  • 3) Three identical lamps are connected in series with a voltage of 120 V (Fig. 163). What is the voltage on each of them?
  • A) 360 V; B) 120 V; B) 60 V; D) 4 V; E) 40 V.
  • 4) Figure 164 shows a stepped rheostat, in which the resistances R 1 \u003d R 2 \u003d R 3 \u003d… \u003d R 5 \u003d 10 Ohm. Calculate the resistance at a given position of the moving contact K.
  • A) 20 Ohm; B) 50 Ohm; B) 40 Ohm; D) 30 Ohm; E) 3.3 ohms.
  • 5) Electric lamp resistance R and the ammeter was connected to a 200 V network as shown in Figure 165. Calculate the resistance R , if the ammeter shows a current of 0.5 A. The lamp resistance is 240 ohms.
  • A) 120 Ohm; B) 160 Ohm; B) 260 Ohm; D) 60 Ohm.

  • A resistor of 2 (Ohm) is connected in a 12V circuit. What resistance should one more resistor be connected so that the current strength is 2A

Repetition: serial connection of conductors

  • In a circuit with a voltage of a 12V source, two resistors and a light bulb are connected. The voltage on the light bulb is 5V, on the first resistor is 3V. The resistance of the second resistor is 6 (Ohm). Determine the resistance of the first resistor and light bulb

  • The current in the unbranched part of the circuit is equal to the sum of the currents in the branches
  • The voltage in all parallel sections is the same
  • The reciprocal of the total resistance is equal to the sum of the reciprocal values \u200b\u200bof the resistances of all parallel sections


Tasks for parallel connection of consumers



The resistances of the resistors are respectively equal to 4.6.12 (Ohm). Determine the current strength in each resistor if the voltage between points A and B is 24V. Determine the current in the unbranched part of the circuit



The currents in the resistors are respectively equal to 2A, 1.5A, 3A. Determine the resistance of the resistors if the voltage between points A and B is 16V.


D / s § 48,49 exercise 22 (1,2), exercise 23 (3)

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Slide 2

Series connection of conductors

With a series connection of conductors, the end of one conductor is connected to the beginning of another, etc. The figures show a chain of series connection of two lamps and a diagram of such a connection. If one of the bulbs burns out, the circuit will open and the other bulb will go out.

Slide 3

Serial connection laws

When the conductors are connected in series, the current strength in all sections of the circuit is the same: According to Ohm's law, the voltages U1 and U2 on the conductors are equal: The total voltage U on both conductors is equal to the sum of the voltages U1 and U2: where R is the electrical resistance of the entire circuit. It follows from this: When connected in series, the total resistance of the circuit is equal to the sum of the resistances of the individual conductors.

Slide 4

Parallel connection of conductors

When the conductors are connected in parallel, their beginnings and ends have common points of connection to the current source.

Slide 5

Laws of parallel connection of conductors

When connected in parallel, the voltages U1 and U2 in all sections of the circuit are the same: The sum of the currents I1 and I2 flowing through both conductors is equal to the current in the unbranched circuit: Writing based on Ohm's law: where R is the electrical resistance of the entire circuit, we get , the reciprocal of the total resistance of the circuit, is equal to the sum of the values \u200b\u200bopposite to the resistances of the parallel-connected conductors.

Slide 6

Task 1 Two conductors are connected in series. The resistance of one conductor is R \u003d 2 ohms, the other is R \u003d 3 ohms. The reading of the ammeter connected to the first conductor is I \u003d 0.5 Ohm. Determine the current flowing through the second conductor, the total current in the circuit, the total voltage of the circuit.

Slide 7

The solution of the problem

Given: R1 \u003d 2 Ohm R2 \u003d 3 Ohm I1 \u003d 0.5 A Solution: I1 \u003d I2 \u003d Iu; I2 \u003d Iu \u003d 0.5 AU1 \u003d I1R1; U1 \u003d 0.5 x 2 \u003d 1 (V) U2 \u003d I2R2; U2 \u003d 0.5 x 3 \u003d 1.5 (V) Uu \u003d U1 + U2; Uu \u003d 1 + 1.5 \u003d 2.5 (V) I2, Iu, Uu \u003d? Answer: I2 \u003d Iu \u003d 0.5 A, Uu \u003d 2.5 V.

Slide 8

Objective 2.

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    Slide 14

    Objective 3.

    Dr. Watson and Sherlock Holmes were invited by friends on New Year's Eve. And, suddenly, as one of Murphy's laws says: "Everything that needs to break will surely break, and at the most inopportune moment." And what happened? When the owner of the house began to turn on the Christmas tree garland for the children, one of the 3.5 V bulbs burned out. The children are upset, the owner is in a panic, because there is no spare light bulb at hand. We must save the holiday, Holmes decided. And, asking everyone to calm down, Holmes spoke the magic words and did one action. To the delight of the children, the garland lit up. Later, Dr. Watson asked Holmes, what did he do? What did Holmes answer?

    Slide 15

    Advantages and disadvantages of connections

    Example of serial connection: garland. An example of a parallel connection: lamps in a study. Advantages and disadvantages of connections: Parallel - when one lamp burns out, the rest are on. But when you turn on the lamp with the lower possible voltage, it will burn out. Sequential - lamps with a lower possible voltage are included in a circuit with a higher voltage, but when one lamp burns out, all will not burn.

    Slide 16

    Homework:

    Give examples of serial and parallel connections of conductors in your home. Repeat. § 48, 49. Exercise. 22 (2), exercise 23 (3.4).

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    Experience has shown the relationship between current strength, voltage and resistance in series connection. There are wiring diagrams for serial connection and solving problems according to these diagrams.

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    "Presentation for the lesson" Serial connection of conductors. "



    Symbol

    Name

    Galvanic

    Resistor

    Ammeter

    Voltmeter


    Physical quantities and their letter designations.

    Current strength

    Voltage

    Resistance


    Ampere

    Volt

    Current strength

    Voltage

    Resistance


    Physical quantities and devices for their measurement.

    Ammeter

    Voltmeter

    Current strength

    Voltage


    Georg Simon Ohm

    Famous German physicist



    Current (A)

    I 1

    I 2

    Voltage (V)

    U 1

    U 2

    Resistance (Ohm)

    R 1

    R 2


    • With a series connection, the current in any part of the circuit is the same, i.e.

    I = I 1 = I 2 .

    The total voltage in the circuit when connected in series, or the voltage at the poles of the current source, is equal to the sum of the voltages in individual sections of the circuit:

    U \u003d U 1 + U 2

    • The total resistance of the circuit when connected in series is equal to the sum of the resistances of the individual conductors:

    R \u003d R 1 + R 2 .




    15 Ohm

    20 Ohm



    1. According to the scheme shown in fig. 17, define

    ammeter reading and total resistance

    in the electrical circuit if R 1 \u003d 5 Ohm, R 2 \u003d 3 ohms.

    2. What are the ammeter readings and general

    electrical circuit resistance,

    shown in Fig. 18, if a R 1 \u003d 10 Ohm, R 2 \u003d 2 ohms?

    3. According to the scheme shown in fig. 21,

    determine the ammeter reading and

    resistance R2, if R1 \u003d 4 ohms.

    The purpose of the lesson: 1. To acquaint students with the serial and parallel connection of conductors. 2. Regularities existing in a circuit with serial and parallel connection of conductors. Application 3. To teach to solve problems on the topic: Serial and parallel connection of conductors 4. To consolidate the knowledge of students about the various connections of conductors and to form the ability to calculate the parameters of combined circuits




















    Advantages and disadvantages of a series connection Advantages: Having elements designed for low voltage (for example, light bulbs), you can connect them in series in the required number and connect to a source with high voltage (this is how Christmas tree garlands are arranged) Disadvantage: It is enough for one device (or element) to get out of when the circuit is broken and all other devices do not work








    Advantages and disadvantages of parallel connection Advantages: If one of the branches fails, the rest continue to work. In this case, each branch can be connected and disconnected separately. Disadvantage: You can turn on devices designed only for this voltage




    Application of a serial connection The main disadvantage of a serial connection of conductors is that if one of the connection elements fails, the rest are turned off.For example, if one of the lamps of a Christmas tree garland burns out, then all the others will go out. The indicated disadvantage can turn into an advantage some circuit needs to be protected against overload: when the current increases, the circuit should automatically shut down How to do this? (How to do this? (For example, use fuses) Give examples of applications for serial connection of conductors


    Application of parallel connection A wide variety of consumers of electrical energy can be connected in parallel in the same electrical circuit. Such a connection scheme for current consumers is used, for example, in living quarters. Question to students: How are electrical appliances interconnected in your apartment?


















    Can two identical 110 V lamps be used on a 220 V network? How? How many identical resistors were connected in series if each of them has a resistance of 50 ohms, and their total resistance is 600 ohms? Two resistors with resistances of 5 ohms and 10 ohms are connected in parallel to the battery. The current strength in which of them is greater? How will the resistance of the electrical circuit change if another resistor is connected to any link in the circuit: a) in series b) in parallel? How do you connect four resistors with 0.5 ohm, 2 ohm, 3.5 ohm, and 4 ohm resistance so that their total resistance is 1 ohm? Knowledge check



     

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