"Resistors and Rheostats" Exploring Circuit PPT Courseware 2

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"Resistors and Rheostats" Exploring Circuit PPT Courseware 2

The teacher connects each component on the circuit board to the circuit respectively. You carefully observe the changes in the brightness of the light bulb and think about the following questions:

How does a change in the brightness of a light bulb indicate a change in the current flowing through it? What does the change in current in the circuit indicate?

induction:

All components can conduct electricity, but their conductive properties are different. Everything has two sides, and the same is true for conductors. While conducting electricity, they also hinder current flow.

1. Resistance (R)

1. Concept

Indicates the resistance of a conductor to current flow.

The greater the conductor resistance, the greater the resistance of the conductor to current flow, and the smaller the current in the circuit.

The smaller the conductor resistance, the smaller the resistance of the conductor to the current, and the greater the current in the circuit.

2. Unit

SI unit: ohm, referred to as ohm, symbol Ω.

Commonly used units: kiloohms (KΩ) megaohms (MΩ)

1KΩ＝1000Ω　1MΩ＝1000KΩ

3. Application

A component with a certain resistance value - a resistor, referred to as a resistor. The symbol is _____.

Function: Used to regulate the current and voltage in the circuit.

2. Research experiments

Ask the question: What are the factors that determine the size of a resistor?

Guess: The resistance may be related to the material of the conductor; it may also be related to the cross-sectional area and length of the conductor; maybe it is related to the temperature.

Plan and design experiments:

1. What methods are used to conduct research in experiments?

Use the method of controlling variables to study the impact of each factor on the resistance size

2. How to determine the size of the resistance in the experiment?

Use an ammeter to measure the magnitude of the current flowing through the conductor for comparison, while keeping the voltage of the circuit constant.

Conduct experiments and collect evidence

Explore the relationship between resistor size and cross-sectional area

Design experimental plan

In this study, the _______ and _______ of the conductor should be controlled constant, and then the change in conductor resistance when the cross-sectional area of ​​the conductor changes.

Experimental conclusion: When the material length of the conductor is the same, the larger the cross-sectional area, the smaller the resistance.

Explore the relationship between resistor size and length

Design experimental plan

In this study, we should control the ______ and _______ of the conductor unchanged, and then study the changes in the conductor resistance when the length of the conductor changes.

Experimental conclusion: When the cross-sectional area of ​​the conductor material is the same, the longer the length, the greater the resistance.

Explore whether the resistance size is related to the material of the conductor

Design experimental plan

In this study, the _______ and ______ of the conductor should be controlled unchanged, and then the change in conductor resistance when the conductor material changes should be studied.

Experimental conclusion: When the cross-sectional area and length of the conductor are the same, the resistance is related to the material.

Relationship between resistance and temperature

Conclusion: For general metal conductors, the resistance of the metal conductor will increase as the temperature increases.

Note: At the junior high school level, unless otherwise specified, the change in resistance value with temperature is not considered.

Summary: (complete the textbook and fill in the blanks)

The resistance of a conductor is ______ with its cross-sectional area. The larger the cross-sectional area of ​​a conductor, the resistance is ______.

The resistance of a conductor is ______ with the length of the conductor. The longer the conductor, the resistance is ______.

The resistance of a conductor depends on the material of the conductor.

Resistance is also related to the temperature of the conductor. The higher the temperature of most conductors, the resistance______.

So: Resistance is a property of the conductor itself. For a fixed-value resistor, its resistance has nothing to do with the applied voltage and the passing current.

Knowledge and Application:

1. Which of the following statements is correct:

A. Sliding rheostat is better than resistor box

B. Two copper wires with different thicknesses, the thinner one has greater resistance

C. The resistance box can gradually change the resistance connected to the circuit

D. Before connecting the circuit and closing the switch, the resistance of the sliding rheostat connected to the circuit should be maximized.

2. Among the sliding rheostat shown in the figure below, the resistance in the circuit can be changed by moving the slider of the sliding rheostat:

3. As shown in the figure below, when the slider P of the sliding rheostat slides to the right, the resistance value of the sliding rheostat connected to the circuit will be:

A. Gradually become larger B. Gradually become smaller

C. Remain unchanged D. Unable to judge

4. As shown in the figure below, when the switch is closed, slide the slider P of the sliding rheostat to the right, and the ammeter will read:

A. Gradually become larger B. Gradually become smaller

C. Remain unchanged D. Unable to judge

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For more information about the "Exploring Circuit Resistors and Rheostats" PPT courseware, please click the Explore Circuit PPT Resistors and Rheostats PPT tab.

"Resistors and Rheostats" Exploring Circuit PPT Courseware 4:

"Resistors and Rheostats" Exploration Circuit PPT Courseware 4 Demonstration Experiment 1. Observe the brightness changes of the dimmer light 2. Listen to the changes in the volume of the speaker. Think about it. If you move the wire clip along the pencil lead, how will the brightness of the small light bulb change? Why do you think the brightness of the light bulb changes like this?

"Resistors and Rheostats" Exploring Circuit PPT Courseware 3:

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"Resistors and Rheostats" exploring circuit PPT courseware:

"Resistors and Rheostats" Exploring Circuit PPT Courseware 1. Resistance 1. Concept: The _____ effect of a conductor on current is called resistance. Represented by the letters _____. 2. Unit: The international unit of resistance is _____, the abbreviation of _____ symbol is _____. Commonly used units include _____( ) and _..

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Update Time: 2024-10-17

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