Mikhail An was appointed first deputy general director of VDNKh JSC for congress and exhibition activities - "informexpo"
Minister of Economy and Finance of the Moscow Region. Education: 2002 Drexel University (USA), majoring in Finance,...
Purpose of the lesson: 1. To introduce students to the serial and parallel connection of conductors 2. The laws that exist in a circuit with a serial and parallel connection of conductors. Application 3. Teach how to solve problems on the topic: Series and parallel connection of conductors 4. Consolidate students’ knowledge of various conductor connections and develop 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 quantity and connect them to a source with a high voltage (this is how Christmas tree garlands are arranged) Disadvantage: It is enough for one device (or element) to come out of building, the circuit opens and all other devices do not work
Advantages and disadvantages of a parallel connection Advantages: If one of the branches fails, the rest continue to work. Moreover, each branch can be connected and disconnected separately. Disadvantage: You can turn on devices designed only for a given voltage
Using a series connection The main disadvantage of a series connection of conductors is that if one of the connection elements fails, the rest are switched off. So, for example, if one of the lamps of a Christmas tree garland burns out, then all the others will go out. This disadvantage can also turn into an advantage Imagine that some circuit needs to be protected from overload: when the current increases, the circuit should automatically turn off How to do this? (How to do this? (For example, use fuses) Give examples of the use of series connection of conductors
Application of parallel connection A variety of consumers can be connected in parallel to the same electrical circuit electrical energy This scheme for connecting current consumers is used, for example, in residential premises. Question to students: How are electrical appliances connected to each other in your apartment?
Slide 2
When connecting conductors in series, the end of one conductor is connected to the beginning of another, etc. The pictures show a circuit connecting two light bulbs in series 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
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: With a series connection, the total resistance of the circuit is equal to the sum of the resistances of the individual conductors.
Slide 4
When conductors are connected in parallel, their beginnings and ends have common connection points to the current source.
Slide 5
With a parallel connection, the voltages U1 and U2 are the same in all sections of the circuit: The sum of the currents I1 and I2 flowing through both conductors is equal to the current in the unbranched circuit: Writing on the basis of Ohm’s law: where R is the electrical resistance of the entire circuit, we obtain When the conductors are connected in parallel, the value , the reciprocal of the total resistance of the circuit, is equal to the sum of the reciprocal values of the resistances of parallel-connected conductors.
Slide 6
Problem 1Two conductors are connected in series. The resistance of one conductor is R = 2 Ohms, the other is R = 3 Ohms. The reading of the ammeter connected to the first conductor is I = 0.5 Ohm. Determine the current flowing through the second conductor, the total current in the circuit, and the total voltage in the circuit.
Slide 7
Given: R1= 2 OhmR2= 3 OhmI1= 0.5 AR Solution: I1= I2= Iu; I2= Iu= 0.5 AU1= I1R1; U1= 0.5 x 2= 1 (V)U2= I2R2; U2= 0.5 x 3= 1.5 (V)Uu= U1+U2; Uu= 1+1, 5 = 2.5 (V) I2, Iu, Uu=? Answer: I2= Iu= 0.5 A, Uu= 2.5 V.
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Doctor Watson and Sherlock Holmes were invited to visit friends on New Year's Eve. And, suddenly, as one of Murphy’s laws says: “Everything that is supposed to break will definitely 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 light bulbs designed for a voltage of 3.5 V burned out. The children were upset, the owner was in a panic, because there was no spare light bulb at hand. We must save the holiday, Holmes decided. And, asking everyone to calm down, Holmes uttered the magic words and did one action. To the universal joy of the children, the garland caught fire. Later, Dr. Watson asked Holmes what he did? What did Holmes answer?
Slide 15
Example of a serial connection: garland. Example of parallel connection: lamps in an office. Advantages and disadvantages of connections: Parallel - when one lamp burns out, the rest burn out. But if you turn on a lamp with a lower possible voltage, it will burn out. Series - lamps with a lower possible voltage are included in a circuit with a higher voltage, but if one lamp burns out, all of them will not light.
Slide 16
Give examples of series and parallel connections of conductors in your home. Rep. § 48, 49. Ex. 22 (2), exercise 23 (3,4).
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Secondary school No. 20 Position: physics teacher Sequential compound conductors compound conductors without branches, when the end of one conductor connected to the beginning of another conductor. At sequential connection conductors: - the strength of the current flowing through each...
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Repetition
Chizhova Vera Alexandrovna
Physics and computer science teacher
MBOU secondary school in Krasnoe village,
Nenets Autonomous Okrug.
Laws of series connection of conductors
Repetition: series connection of conductors
Tasks for parallel connection of consumers
The resistor resistances are respectively 4,6,12(Ohm). Determine the current in each resistor if the voltage between points A and B is 24V. Determine the current strength in the unbranched part of the circuit
The current strengths in the resistors are respectively 2A, 1.5A, 3A. Determine the resistance of the resistors if the voltage between points A and B is 16V.
D/z § 48,49 exercise 22(1,2), exercise 23(3)
The experiment shows the relationship between current, voltage and resistance in a series connection. There are electrical circuits for serial connections and solutions to problems using these circuits.
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 instruments 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
I = I 1 = I 2 .
The total voltage in the circuit in a series connection, 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 = U 1 +U 2
R = R 1 + R 2 .
15 Ohm
20 Ohm
1. According to the diagram shown in Fig. 17, determine
ammeter readings and total resistance
in an electrical circuit, if R 1 = 5 Ohm, R 2 = 3 Ohm.
2. What are the ammeter readings and general
electrical circuit resistance,
shown in Fig. 18, If R 1 = 10 Ohm, R 2 = 2 Ohm?
3. According to the diagram shown in Fig. 21,
determine the ammeter readings and
resistance R2, if R1 = 4 Ohms.