In the experiment of exploring the relationship between current and resistance, the slide of sliding rheostat is adjusted to keep the voltage at both ends of the resistance unchanged. If the voltage does not change, does not the current also change? Does not the calculated resistance also change?

In the experiment of exploring the relationship between current and resistance, the slide of sliding rheostat is adjusted to keep the voltage at both ends of the resistance unchanged. If the voltage does not change, does not the current also change? Does not the calculated resistance also change?

The slide of sliding rheostat is adjusted to keep the voltage at both ends of constant value R. in the experiment, it is necessary to use different constant value R. for example, suppose the power supply voltage is 4 v. at the beginning, the constant value R is 10 Ω, and the voltmeter reading at both ends of R is 2 V, which means that the reading of ammeter is 0.2 A. at the same time, the resistance of sliding rheostat can be calculated as (4-2) / 0.2 = 10 beats, If the resistance of the sliding rheostat remains unchanged, the total current is 4 / (20 + 10) = 4 / 30 A, and the reading of the voltmeter at both ends of R should be 20 × 4 / 30 = 8 / 3 ≈ 2.67 v. to keep the reading of the voltmeter at both ends of the constant resistance R (U = 2V), the slide of the sliding rheostat must be adjusted to ensure that the voltage at both ends of R is 2 v. at this time, the reading of the ammeter is 2 / 20 = 0.1 A, and the resistance of the sliding rheostat is (4-2) / 0.1 = 20 Ω, That is to say, when the constant resistance increases, the slide of sliding rheostat will slide in the direction of increasing resistance until the voltmeter at both ends of R reaches the required value
To explore the relationship between current and resistance is to study the law of how the current changes when the resistance changes, rather than to calculate the resistance value (the resistance value studied is given, that is, the constant resistance). So in the experiment, we need to use different constant resistance R. you ignore this premise and get the following conclusion: "if the voltage does not change, then the current does not change, In fact, in order to keep the voltage at both ends of the constant resistance unchanged, we should adjust the slide of the sliding rheostat (change the resistance value) to change the total current so that the product (voltage) of the total current and the constant resistance R remains unchanged

Excuse me, in the process of exploring the relationship between "when the resistance is fixed, the current through the resistance and the voltage at both ends", what is the purpose of using sliding rheostat

Protection circuit, adjust the resistance voltage, and then control the current

In a circuit, the power supply voltage is 6V, the range of ammeter is 0-0.6a, the range of voltmeter is 0-3v, the resistance of bulb is 8ohm, and the sliding rheostat is the largest
In a circuit, the power supply voltage is 6V, the range of ammeter is 0-0.6a; the range of voltmeter is 0-3v, the bulb resistance is 8ohm, and the maximum resistance of sliding rheostat is 20. In the process of moving the slide, in order not to damage the ammeter, what range should the resistance of sliding rheostat be connected to (detailed steps)

The lamp is connected in series with the rheostat
When the lamp voltage is 3V, the rheostat voltage is 3V, and the rheostat resistance is equal to 8 Ω
At this time, the current is I1 = u / (r Lamp + R transformer) = 6 / (8 + 8) = 3 / 8 a ＜ 0.6A
In order not to damage the meter, the resistance value of sliding rheostat should be greater than or equal to 8 Ω, 8 Ω ≤ R ≤ 20 Ω

The range of 0-0.6a is used for the constant supply voltage ammeter, and the 3V small bulb is used for the voltmeter, marked with 2.5v1.25w. The maximum resistance of the sliding rheostat is 20 Ω
When 4 Ω is connected, the small bulb works normally and the resistance value of R1 is calculated. The power supply voltage can change the working state of bulb L by adjusting R, but it must be ensured that the ammeter voltmeter does not exceed the range and the resistance value of R1 is calculated

Unable to answer, there must be a circuit diagram, the circuit diagram in physics is more useful than that in mathematics!