"Scientific Exploration: Ohm's Law" Exploring Circuit PPT Courseware 4

Description

"Scientific Exploration: Ohm's Law" Exploring Circuit PPT Courseware 4

Knowledge preparation

You must still remember:

1. Voltage is the cause of _______.

2. Resistance represents the resistance of a conductor to ________.

question

So is there a certain relationship between the current passing through a certain conductor, the voltage across the conductor, and the resistance of the conductor?

1. Observe the following experiments and think about them

Phenomenon: When powered by two batteries, the light bulb glows more____;

Analysis: As the voltage across the bulb increases, the current in the bulb _____.

2. Observe the following experiments and think about them

Current is related to resistance. When the resistance in a circuit increases, the current in the circuit _________.

From the above experiments we see:

The current in a circuit is related to voltage and resistance. The current in the circuit increases as the voltage increases and decreases as the resistance increases.

So, what is the quantitative relationship between them?

In this lesson we explore this relationship through experiments.

1. Experiment to explore the relationship between current, voltage and resistance

Current is affected by voltage and resistance at the same time. What method should we use to study the influence of each factor?

Determine the research method: control variable method

specific methods:

1. Control the resistance to be constant and explore the relationship between current and voltage.

2. Control the voltage to be constant and explore the relationship between current and resistance.

1. Experiment to explore the relationship between current and voltage

design experiment

To measure the voltage across a resistor, what equipment should I choose?

How to change the voltage across a resistor? How to operate?

To measure the current through a resistor, what equipment should I choose?

What are the invariants during the experiment and how to control them?

What role does the sliding rheostat play in the experiment?

2. Experiment to explore the relationship between current and resistance

Experimental steps

(1) Connect the circuit according to the circuit diagram;

(Note: Before connecting the circuit, turn off the switch and move the sliding rheostat slide to the maximum value. Select the appropriate range and correct binding posts for the ammeter and voltmeter.)

(2) Write down the resistance value (such as 5Ω), close the switch, and move the slider of the sliding rheostat so that the voltmeter indicates a certain value (such as 2V). Note down the ammeter's indication and record the data in the table. ;

(3) Replace a new resistor, write down its resistance value (for example, 10Ω), move the slider of the sliding rheostat so that the voltmeter's indication remains unchanged (for example, it is still 2V), note down the ammeter's indication, and put Data are recorded in tables;

(4) Replace a new resistor, note its resistance value (such as 15Ω), and repeat the last experiment.

Experimental circuit diagram

1. The function of the sliding rheostat: to keep the voltage across R unchanged

2. Equipment to be replaced in the circuit during the experiment

R size

Experimental conclusion 2:

When the voltage is kept constant, the current is related to the resistance.

practice

1. When the voltage across a conductor increases several times, the current flowing through it will ___ ____; when the voltage across the conductor changes, the conductor resistance will _______.

2. In the experiment of "Studying the Relationship between Current, Voltage and Resistance", we first set the resistance to a certain value, change the resistance value of the sliding rheostat multiple times, record each current value and the corresponding ______ value, and get When the resistance remains constant, the current is proportional to ____. Then change the resistance value of the resistor several times and adjust the slider of the sliding rheostat so that ______ remains unchanged each time. Record the resistance value R and The corresponding ____ value is that the current is inversely proportional to _____.

3. Which statement about the relationship between voltage and current is incorrect ( )

A Voltage is what causes current in a circuit

B The current in a conductor is directly proportional to the voltage and inversely proportional to the resistance

C When the resistance is constant, the voltage across the conductor is proportional to the current

D When the resistance is constant, the conductor current is proportional to the voltage across the conductor

4. The picture in the picture is the U-I image drawn by Xiao Ming using the measured data when studying the relationship between current and voltage. From the picture, it can be seen that the size relationship between R1 and R2 is ( )

A R1>R2

B R1

C R1=R2

D Unable to determine

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Update Time: 2024-08-06

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