"Laws of Current in Series and Parallel Circuits" Current and Circuit PPT Teaching Courseware

Description

"Laws of Current in Series and Parallel Circuits" Current and Circuit PPT Teaching Courseware

Part One: Knowledge Management

1. Explore the laws of electric current

Exploration: Ask questions, conjectures and hypotheses, design experiments (draw a circuit diagram, design a table to record experimental data), conduct experiments (connect the physical diagram according to the circuit diagram, connect the ammeter according to "positive in and negative out", select the appropriate range, Objective and accurate reading), analysis and induction, summary and demonstration.

Note: Multiple measurements must be made with different light bulbs, and conclusions can be drawn by summarizing multiple sets of experimental data.

① Pay attention to the correct connection of the ammeter in the circuit; ② When connecting the circuit, the switch should be turned off; ③ After the circuit is connected, use the switch test method to select the appropriate range of the ammeter before measuring; ④ After each measurement of data, the switch should be turned off. open.

2. Current law

Series: The current in a series circuit is equal everywhere. I＝I1＝I2

Parallel connection: The current in the trunk of a parallel circuit is equal to the sum of the currents in each branch. I＝I1＋I2

PPT on the laws of current in series and parallel circuits, part 2: classification and exploration

Type 1: Understand the laws of current flow in series circuits

When "exploring the relationship between the currents at various points in a series circuit", Xiao Ming designed the experiment as follows: connect two light bulbs L1 and L2 in series and connect them to the circuit as shown in the figure, and connect points A, B, and C in the figure respectively. Disconnect, connect, measure the current flowing, and see how they relate to each other. Replace the other two small light bulbs and measure the three points again to see if there is still the same relationship.

The table below is the experimental data of two measurements.

Item Current IA at point A Current IB at point B Current IC at point C

First measurement 0.3 A 0.3 A 0.3 A

Second measurement 0.2 A 0.2 A 0.2 A

Analysis and argumentation:

(1) When disconnecting the circuit, switch S must be in the state.

(2) Conclusion: Everything in the series circuit is equal.

[Analysis] Explore the current law in a series circuit, use an ammeter to measure the current in each part of the series circuit, and conduct multiple experiments using electrical appliances of different specifications, analyze the experimental data, and draw experimental conclusions.

[Method Summary] When the specifications of two light bulbs are the same, regardless of whether they are connected in series or in parallel, the current is the same. In order to avoid special (accidental) characteristics in the experiment, multiple measurements need to be made with light bulbs of different specifications. When the ammeter is used, the current measured cannot exceed the maximum range of the ammeter. The current must flow in from the "+" terminal of the ammeter and flow out from the "-" terminal.

Type 2: Understand the current laws in parallel circuits

[2017•Chengdu, Sichuan]The experimental circuit of "Exploring the current relationship of parallel circuits" is shown in Figure 1.

(1) In order to make the conclusions drawn from the investigation have universal significance, L1 and L2 should choose (optional "same" or "different") small light bulbs.

(2) Connect the circuit according to Figure 1, connect the ammeter to point C, close the switch, and find that the ammeter pointer is as shown in Figure 2. The reason for this phenomenon is .

(3) After the measurement is completed, conduct group exchange and discussion. The following table selects the data of four groups. Do you think these data are reasonable? Please explain the reasons. .

[Analysis] (1) In order to make the conclusions drawn from the investigation have universal significance, L1 and L2 should choose different small light bulbs.

(2) Connect the circuit according to Figure 1, connect the ammeter to point C, close the switch, and find that the ammeter pointer is as shown in Figure 2. The reason for this phenomenon is that the ammeter pointer is not zeroed or the ammeter is wired "+" and "-" The column is connected backwards.

(3) After the measurement is completed, group exchanges and discussions are held. The selected data of the four groups are reasonable because there are errors in the experimental measurement.

(4) It can be seen from the table that the main circuit current is equal to the sum of the branch currents, that is, IC = IA + IB.

[Method Summary] (1) Using the inductive method to draw universal conclusions must meet two conditions: first, the sample must be representative, and second, the number of samples must be large enough; (2) further clarify the main circuit current in the parallel circuit through experiments Is equal to the sum of the currents in each branch.

The law of current in series and parallel circuits PPT, the third part: evaluation in class

1. [2019•Tongzhou District, Beijing]When exploring the laws of current in series circuits, the circuit is as shown in the figure. Close the switch and use an ammeter to measure the currents at A, B, and C as IA, IB, and IC respectively. Regarding their size relationship, the correct one is ()

A. IA=IC B. IA＜IB

C. IA＜IC D. IB>IC

2. [2019•Tongren, Guizhou]In the circuit shown in the figure, the reading of ammeter A1 is 0.5 A, and the reading of ammeter A2 is 0.7 A. Then, the reading of ammeter A should be ()

A. 1.2 A B. 0.5A

C. 0.7 A D. 0.2 A

3. [2019•Shandong Binzhou]In the circuit as shown in the figure, after closing the switch, the pointers of the two ammeters deflect normally and at the same deflection angle. At this time, the ratio of the currents of lamps L1 and L2 is ()

A. 1:5 B. 1:4

C. 5:1 D． 4:1

4. [2019•Changde, Hunan] Two light bulbs with the same specifications are connected to the circuit. Their currents are both 0.46 A measured with an ammeter. The total current in the circuit is ()

A. It must be 0.46 A

B． It must be 0.92 A

C. Both 0.46 A and 0.92 A are possible

D． None of the above statements are correct

PPT on the laws of current in series and parallel circuits, part 4: layered work

1. [2019•Shandong Linyi]As shown in the figure, when exploring the current relationship in a parallel circuit, Xiao Ming connected two light bulbs with different resistances to the circuit, and used an ammeter to measure the current through A, B, The currents at three points C are IA, IB, and IC respectively. Regarding the size relationship between them, the correct one is ()

A. IA＝IB＝IC B. IA>IB＝IC

C. IA＝IB＋IC D． IA＜IB＜IC

2. [2019•Guangdong Shenzhen]As shown in the figure, the maximum currents allowed to pass through the resistors R1, R2, and R3 connected to the circuit are I1, I2, and I3 respectively, and I1>I2>I3, then this The maximum current allowed to pass through the circuit is ()

A. I1B． I2

C. I3D. I1＋I2＋I3

3. [2019•Jiangsu Yancheng] Xiaohong connected the circuit as shown in the picture. After closing the switch S, he found that L1 was very bright and L2 could only glow weakly. Regarding the current passing through L1 and L2, the following statement is correct of is()

A. The current through L1 is greater than the current through L2

B． The current through L1 is equal to the current through L2

C. The current through L1 is less than the current through L2

D． Unable to judge

4. [2019•Shaoyang, Hunan]Which of the following statements is correct ()

A. The current flowing through the two lamps is equal, then the two lamps must be connected in series.

B． The currents in a series circuit may not be equal everywhere

C. In a parallel circuit, the current in the main circuit must be greater than the current in any branch.

D． The currents in each branch of a parallel circuit must be equal

5. [2019•Nanjing, Jiangsu] Connect the two ammeters to the two positions as shown in Figure A for measurement. At this time, the readings of ammeters A1 and A2 are as shown in Figure B respectively. Through the bulbs L1 and L2 The current magnitudes are ()

A. 0.24A,0.7A

B． 1.2A,0.7A

C. 0.24A,0.46A

D． 1.2A,0.14A

[Analysis] It can be seen from the circuit diagram that two light bulbs are connected in parallel, ammeter A1 measures the current of the L1 branch, and ammeter A2 measures the main circuit current. Because the main circuit current in a parallel circuit is equal to the sum of the branch currents, that is, the main circuit current is greater than the current of any branch, and judging from the deflection positions of the two ammeter pointers, the deflection angle of A2 is smaller than A1, so the ammeter A1 The measuring range is 0 to 0.6 A, the graduation value is 0.02 A, and the indication is 0.24 A, that is, the current I1 passing through the lamp L1 = 0.24 A; the ammeter A2 has a measuring range of 0 to 3 A, the division value is 0.1 A, and the indication is is 0.7 A, that is, the main circuit current I=0.7 A. According to the current law of the parallel circuit: I=I1+I2, the current through the lamp L2: I2=I-I1=0.7 A-0.24 A=0.46 A.

Keywords: Free download of PPT courseware for ninth-grade physics from the People's Education Press, PPT download of current and circuits, PPT download of the laws of current in series and parallel circuits, .PPT format;

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Update Time: 2024-11-23

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