"End of Chapter Review" Ohm's Law PPT

Description

"End of Chapter Review" Ohm's Law PPT

Part One: Knowledge Versatility

1. Two important experiments

(1) Explore the relationship between current, voltage, and resistance

Experimental circuit diagram: As shown in Figure 17-Z-1.

Experimental method: controlled variable method.

Experimental conclusion: When the resistance is constant, the current through the conductor is proportional to the voltage at both ends of the conductor; when the voltage is constant, the current through the conductor is inversely proportional to the resistance of the conductor.

(2) Measure resistance by voltammetry

Experimental principle: R=U/I.

Experimental circuit diagram: As shown in Figure 17-Z-2.

2.Three formulas

(1) Ohm’s law formula: I=UR.

(2) The series connection formula of resistors: R=R1+R2+……+Rn.

(3) The parallel formula of resistors: 1R=1R1+1R2+……+1Rn.

Review PPT at the end of the chapter, part 2 content: Practical high school entrance examination

Test Point 1: Determine the changes in electric meter values

The problem of changes in the electric meter value in the circuit caused by the movement of the sliding blade of the sliding rheostat or the opening and closing of the switch has been the focus of the examination in the past years, usually in the form of multiple-choice questions or fill-in-the-blank questions. The steps to solve the problem are as follows:

(1) Analyze the connection method of the circuit and clarify the measurement objects of each meter.

(2) Analyze the circuit changes caused by the movement of the slide or the closing and opening of the switch.

(3) Further qualitative analysis of the changes in electrical meter numbers, or quantitative calculations based on the question conditions.

Example 1 [Shenzhen High School Entrance Examination] As shown in Figure 17-Z-3, keeping the power supply voltage unchanged, when the switch S changes from open to closed, the following statement is correct ( )

A． The number expressed by the current remains unchanged, but the number expressed by the voltage becomes larger.

B． The number represented by the current becomes larger, but the number represented by the voltage remains unchanged.

C. The current indication number becomes larger, and the voltage indication number becomes larger.

D. The number represented by current remains unchanged, and the number represented by voltage remains unchanged.

Example 2 [Fuzhou High School Entrance Examination] As shown in Figure 17-Z-4, the power supply voltage remains unchanged, the switch S is closed, and when the sliding varistor slide P moves to the right ( )

A． The indication of ammeter A1 becomes smaller, and the indication of voltmeter V becomes smaller.

B． The indication of ammeter A2 becomes larger, and the indication of voltmeter V becomes larger.

C. The ratio of the reading of voltmeter V to the reading of ammeter A1 remains unchanged.

D. The ratio of the reading of voltmeter V to the reading of ammeter A2 remains unchanged.

Test Point 2 Application of Ohm’s Law

Ohm's law (I=U/R) connects current, voltage, and resistance, and can be used to solve more complex electrical problems in series and parallel circuits. The focus of the examination is the relationship between resistances in series and parallel circuits and the use of Ohm's law and the characteristics of series and parallel circuits to analyze and solve circuit problems. The application of Ohm's law has been a key test subject in the high school entrance examinations over the years, and the test questions include almost all types of questions.

Example 3 Use uniform resistance wires to surround a square ABCD, as shown in Figure 17-Z-5, where E is the midpoint of CD. When two points B and D are connected to the circuit, the total resistance is 8 Ω; then when two points B and E are connected to the circuit, the total resistance is ______Ω.

Example 4 [Chongqing High School Entrance Examination] In the circuit shown in Figure 17-Z-6, the power supply voltage U remains unchanged and the fixed value resistance R=20 Ω. Close the switch S. When the slider P of the sliding rheostat R' is at the midpoint c, the ammeter indicates 0.4 A; when the slider P is moved to the rightmost end, the ammeter indicates 0.3 A. Then the power supply voltage U and sliding

The maximum resistance value of varistor R′ is ( )

A． 6 V 10 Ω B. 6V 20Ω

C. 12V 20ΩD． 12V 40Ω

Example 5 [ Zhuzhou High School Entrance Examination The above is an ammeter with a range of 0~0.6 A), R1 is a varistor, and the image of its resistance changing with the pressure F is shown in Figure B. Its upper surface area is 0.01 m2. The fuel tank is a rectangular parallelepiped, with a depth h of 0.4 m when filled with oil.

(1) From Figure B, it can be seen that the resistance of varistor R1 increases with the increase of pressure F; when the gasoline in the fuel tank is used up, the resistance of R1 is ______Ω.

(2) When the fuel tank is filled with gasoline, what is the pressure and pressure on the upper surface of the varistor? (g is 10 N/kg, ρ gasoline = 0.7×103 kg/m3)

(3) When the fuel tank is filled with gasoline, the fuel quantity indication is the maximum value (that is, the ammeter is full bias). Find the resistance of R0.

(4) When the gasoline in the tank is used up, what is the current in the circuit?

Review the PPT at the end of the chapter, the third part: Entering the majors and high schools

Advantage 1: Determine the composition of the circuit by measuring resistance

Black box circuit problems are relatively complex and are mostly competition test questions. However, in recent years, they have also appeared in high school entrance examination questions in some areas. They focus on testing students' ability to calculate physical quantities in circuits and their comprehensive analysis and judgment ability of circuit connection methods. They need to be meticulous, Rigorous logical thinking.

Typical example 1 (open inquiry question) "Chengdu High School Entrance Examination" There is an electrical black box in the laboratory. Its appearance is shown in Figure 17-Z-13①. There are four terminals outside the box and there are A plastic slider. Xiao Ming asked students in the same group to explore its internal structure. The laboratory teacher reminded them that the internal components only have one sliding rheostat and two fixed-value resistors, and the sliding rheostat has only two binding posts connected to the circuit. After discussion, the whole group's opinion was to first make a detector, connect the detector to the terminals outside the black box, and then speculate on the internal connections based on the measured data.

(1) Xiao Li from Group A assembled the detector, as shown in Figure ②. The power supply voltage is 3 V and the ammeter range is 0~0.6 A. For the resistor R with a resistance of 5 Ω, what do you think its function is? ________________________________________.

(2) In the first three tests, the sliding rheostat was not adjusted to the maximum and minimum resistance positions only once, which was the _________ time.

(3) The maximum resistance value of the sliding rheostat is _________.

(4) Please draw the connection circuit diagram of each component in the box in Figure ③, and mark its resistance value next to the fixed value resistor.

Advantage 2: Application of Ohm’s law in series and parallel circuits

Ohm's law and the characteristics of series and parallel circuits are the core content of junior high school electrical knowledge. Flexible application of this knowledge to solve more complex circuit calculation and design problems is an important test content for physics propositions in the high school entrance examination. It often appears as the final question, focusing on testing students. Mastery of basic electrical knowledge and application ability, and being able to correctly analyze equivalent circuits under different conditions are the key to solving problems.

Typical example 2 (open inquiry question) [Anhui High School Entrance Examination] There is an ammeter G with a full bias current Ig=3 mA, and its resistance Rg=100 Ω is known. Now it needs to be modified into a maximum The ammeter with measured value Ic=3 A is shown in Figure 17-Z-15A. beg:

(1) The resistance of resistor Rx.

(2) The resistance value of the modified ammeter resistor Rc.

(3) As shown in Figure B, connect the modified ammeter to the circuit. It is known that the power supply voltage U=10 V, the resistance R1=5 Ω, close the switch S, and move the slide P of the sliding rheostat to make the ammeter display Number I=1.0 A. At this time, what is the resistance R2 of the sliding rheostat in the circuit and the current I1 passing through the original ammeter G.

Keywords: Free download of PPT courseware for ninth-grade physics from the People's Education Press, download of PPT for end-of-chapter review, download of Ohm's law PPT, .PPT format;

For more information about the "Ohm's Law End of Chapter Review" PPT courseware, please click the Ohm's Law ppt end of chapter review ppt tag.

"Special Method for Measuring Resistance" Ohm's Law PPT:

"Special Methods for Measuring Resistance" Ohm's Law PPT [Topic Overview] Common special methods for measuring resistance include the voltohmometric method, the amperometric method, and the substitution method. The specific measurement methods are as follows: (1) The voltohmic method refers to measuring resistance with How to measure unknown resistance using a voltmeter and a known resistance. ..

"End of Chapter Summary and Improvement" Ohm's Law PPT:

"End of Chapter Summary and Improvement" Ohm's Law PPT Part One Content: Key Breakthrough Type 1 The relationship between current, voltage and resistance 1. As shown in the figure, in the experiment to study the relationship between current, voltage and resistance, a fixed value should be selected first Resistance, by changing the sliding rheostat..

"Application of Ohm's Law in Series and Parallel Circuits" Ohm's Law PPT teaching courseware:

"Application of Ohm's Law in Series and Parallel Circuits" Ohm's Law PPT Teaching Courseware Part One Content: Knowledge Management 1. The total resistance of a series connection of resistors: The total resistance of a series circuit is equal to the sum of the resistances of each part of _____. Formula: R＝R1＋R2. illustrate..

File Info

Update Time: 2024-10-06

This template belongs to Physics courseware People's Education Edition Ninth Grade Physics Complete Book industry PPT template

Preview