"How to Understand Resistance" Exploring Ohm's Law PPT Courseware 2

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"How to Understand Resistance" Exploring Ohm's Law PPT Courseware 2

teaching objectives

1. What is resistance, and what factors are related to the size of resistance.

2. What research methods are used to study resistance.

3. How to use sliding rheostat

Detection Preview 1

1. What factors are related to the resistance size.

2. What method is used to study the resistance size?

Review questions:

How is electric current formed?

The directional movement of charges creates an electric current.

Thinking: The flow of water in a water pipe is subject to resistance, so is the current in a conductor also hindered by the conductor?

1. Resistance:

1. Concept: Resistance represents 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. Symbol: Resistor is represented by R

3. Unit:

(1) International unit: ohm, referred to as ohm, symbol Ω

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

2. What factors are related to resistance?

Conductor resistance has a certain size.

So do you know what factors are related to the resistance of a conductor?

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

Activity 1: Explore what factors are related to the resistance of a conductor

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 a conductor or compare it to the brightness of a small light bulb while keeping the voltage of the circuit constant.

Experimental results

(1) The resistance of a conductor is related to the length of the conductor. When the material and thickness of the conductor are the same, the longer the conductor, the greater the resistance.

(2) The resistance of a conductor is related to the thickness of the conductor. When the material and length of the conductor are the same, the thicker the conductor, the smaller the resistance.

(3) The resistance of a conductor is related to the material. When the thickness and length of the conductor are the same, conductors of different materials have different resistances.

(4) Further research shows that the resistance of conductors is also related to temperature, and the resistance of most metals increases with temperature.

Detection Preview 2

Classification of resistors, use of sliding rheostat

3. Classification of resistors

(1) Fixed value resistor---resistance

(2) Variable resistor---sliding rheostat/resistance box

4. Principle and function of sliding rheostat

1. Function:

(1) Change the size of the current by changing the size of the resistance

(2) Protection circuit

2. Principle: Change the resistance by changing the length of the resistance wire in the access circuit

3. Correct use of sliding rheostat:

(1). Connected in series in the circuit

(2).Connect the two terminals "one up and one down"

(3). The passing current cannot exceed the allowed maximum value

(4). Before use, the slider should be at the maximum resistance point.

What have you gained?

1. The concept of resistance: the degree of resistance of a conductor to current flow.

The symbol of resistance: R.

2. The units of resistance and their conversion.

3. Learned to use the controlled variable method when studying the relationship between one physical quantity and multiple physical quantities.

4. Resistance is a property of the conductor itself. Factors that determine the size of a resistor include length, thickness, material, and temperature.

5. Principle and use of sliding rheostat

practise

1. Fold a metal wire in half and merge it into one. Its resistance will change __ (please fill in "big" or "small"). The reason is that the ______ of the wire does not change, _____ becomes larger, and ______ becomes Caused by small things.

2. After a metal wire is stretched evenly, its resistance will become __ (optional "large" or "small"). The reason is that the ______ of the wire remains unchanged, ______ becomes larger, and ______ becomes smaller.

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For more information about the PPT courseware "Exploring Ohm's Law and How to Understand Resistance", please click the Explore Ohm's Law ppt and How to Understand Resistance ppt tag.

"How to Understand Resistance" Exploring Ohm's Law PPT Courseware 3:

"How to Understand Resistance" Exploring Ohm's Law PPT Courseware 3 Review Question: How can the resistance of a conductor be changed? Which method is easiest? Methods include changing the _________, _________, _________ and _________ of the conductor. And the most convenient thing is to change...

"How to Understand Resistance" Exploring Ohm's Law PPT Courseware:

"How to Understand Resistance" Exploring Ohm's Law PPT Courseware Learning Objectives 1. Know what resistance is, know the units of resistance, and know the factors that determine the resistance of a conductor. 2. Understand the basic structure and principle of the sliding rheostat, and be able to use the sliding rheostat to change the...

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Update Time: 2024-10-16

This template belongs to Physics courseware Guangdong and Shanghai Edition Ninth Grade Physics Volume 1 industry PPT template

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