《Resistance》Voltage resistance PPT

《Resistance》Voltage resistance PPT

Part One Content: Basic Knowledge Key Points

Knowledge point 1 Resistor

1. As shown in the picture, when the copper wire is connected to the circuit, the small bulb is brighter; when the nickel-chromium alloy wire is connected to the circuit, the small bulb is darker. This means that the resistance of the copper wire in the picture is less than (optional "greater than" or "less than" ) the resistance of nichrome wire.

2. Please complete the following unit conversions:

(1)1.6 MΩ=　1.6×106　Ω;

(2)5 kΩ=　5×103　Ω;

(3)2×106Ω=　2MΩ;

(4)60 kΩ=　6×10-2　MΩ.

Knowledge point 2 Factors affecting the size of resistance

3. (Yulin High School Entrance Examination) Which of the following statements about conductor resistance is correct (D)

A. A conductor with a long length must have a high resistance.

B. A conductor with a large cross-sectional area must have a small resistance

C. The resistance of a conductor is determined by the voltage across it and the current flowing through it.

D. The resistance of a conductor is related to factors such as the material, length and cross-sectional area of ​​the conductor

4. A and B are conductors of the same material and the same cross-sectional area. If the length L A < L B, then the size relationship between R A and R B ( B )

A.R A>R B B.R A

C. R A = R B D. Unable to determine

5. Xiaomeng uses the circuit as shown in the picture to explore the relationship between the resistance of the conductor and the material.

(1) Xiaomeng can judge the resistance of different conductors by observing the indications of the ammeter. This research method is the _______ conversion method;

(2) In order to complete the experimental investigation, two conductors ② and ③ (fill in the conductor code) in the figure should be selected and connected to the circuit respectively.

Knowledge point 3 Semiconductors and superconducting phenomena

6. Which of the following substances is a semiconductor material (C)

A.Iron B.Copper C.Silicon D.Plastic

7. Which of the following statements about superconducting materials is correct (B)

A. The resistance of superconducting materials has nothing to do with temperature.

B. The resistance of superconducting materials is zero

C. Superconducting materials can be used to make electric heating wires

D. Superconducting materials are the most advanced semiconductor materials

Resistance PPT, part 2: improvement of comprehensive capabilities

8. When we set up power transmission wires or connect circuits, we should try to keep the length of the wire as short as possible (please fill in "long" or "short") when selecting the route. The reason is that the material, cross-sectional area and When the temperature is constant, the shorter the wire, the smaller the resistance.

9. The materials and lengths of the two wires A and B are the same. The cross-sectional area of ​​A is larger than the cross-sectional area of ​​B, so the resistance of A is smaller than the resistance of B. If they are connected in series in a circuit, the current flowing through A is equal to ( Please fill in "greater than", "less than" or "equal to") the current passing through B.

10. Teacher Liu did a demonstration experiment in class. Experimental equipment: waste incandescent lamp with broken glass bulb but intact tungsten filament, small light bulb L marked with "6 V", battery, switch S, alcohol lamp, matches, and some wires. The connected circuit is as shown in the figure. When the switch S is closed, the small bulb L emits light normally, and then uses an alcohol lamp to heat the tungsten filament of the incandescent lamp. It can be observed that the brightness of the small bulb L dims significantly. At this time, through the The current becomes smaller. This experiment shows that the resistance is related to the temperature of the conductor.

11. (Kunming High School Entrance Examination) According to the conductive properties of materials, materials can be divided into three categories: conductors, semiconductors and insulators; if superconducting wires are used to transmit electrical energy, such wires will not generate heat.

12. (Dalian High School Entrance Examination) The picture shows an electronic thermometer, which reflects a person's body temperature through the current in the temperature sensing head. The temperature sensing head is made of semiconductor material, which is the application of semiconductor (D)

A. One-way conductive characteristics

B. Good insulation properties

C. Characteristics of resistance changing with pressure changes

D. Characteristics of resistance changing with temperature changes

13. (Hezhou High School Entrance Examination) When using the circuit shown in the figure to explore the "factors affecting the size of the resistance" experiment, the following statement is correct (C)

A. In this circuit, a small light bulb cannot be used instead of an ammeter to determine the strength of the current.

B. The experiment only needs to control the materials of the conductors to be the same.

C. This circuit explores the relationship between the resistance of the conductor and the length of the conductor.

D. According to the experiment in the figure, it can be concluded that the resistance of the conductor is related to the material of the conductor.

14. There are three aluminum wires A, B, and C. A and B have the same thickness, A is shorter than B, B and C have the same length, and B is thicker than C. Then the three wires are arranged correctly in the order of their resistance (B)

A.RA>RB>RC B.RC>RB>RA

C.RA>RC>RB D.RC>RA>RB

Resistance PPT, part 3: Expansion, exploration and breakthrough

17. Xiao Zhang explored some of the factors that affect the size of the resistance. The equipment used was: a switch, an ammeter, a dry battery (the voltage is constant at 1.5 V), three identical alloy wires, and several wires. The experimental circuit is shown in Figure A. Xiao Zhang connected the alloy wire between A and B in different ways. After closing the switch S, the recorded data is as shown in the table.

Based on the experimental data, answer the following questions:

(1) Picture B shows the reading of the ammeter when an alloy wire is connected to the circuit. Please fill it in the table;

(2) The relationship between the size of the resistance and the length is: When the material and cross-sectional area are the same, the resistance of the conductor is proportional to the length;

The relationship between the size of the resistance and the cross-sectional area is: When the material and length are the same, the resistance of the conductor is inversely proportional to the cross-sectional area.

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