In the experiment of exploring the relationship between current and voltage, resistance, when exploring the relationship between current and resistance, we should () A. Adjust the sliding rheostat to keep the current in the circuit constant B. Adjust the sliding rheostat so that the voltage at both ends of different fixed resistor R remains unchanged C. Make the voltage at both ends of resistance R change in multiple D. The current in the circuit should be changed in multiple during each measurement

In the experiment of exploring the relationship between current and voltage, resistance, when exploring the relationship between current and resistance, we should () A. Adjust the sliding rheostat to keep the current in the circuit constant B. Adjust the sliding rheostat so that the voltage at both ends of different fixed resistor R remains unchanged C. Make the voltage at both ends of resistance R change in multiple D. The current in the circuit should be changed in multiple during each measurement

B

In the experiment of exploring the relationship between current and resistance under a certain voltage, series power supply, switch, sliding resistor and a fixed value resistor are used. If the fixed value resistor increases, the sliding rheostat resistance will increase or decrease? Why

The resistance value of the sliding rheostat should be increased, because the voltage of the fixed value resistance will increase only by increasing the fixed value resistance value. To keep the voltage of the fixed value resistance unchanged, the sliding rheostat should share more voltage, so the resistance of the sliding rheostat should be increased

Research on the relationship among resistance, current and voltage
I don't know how to keep the voltage constant,
In addition, by connecting the fixed resistors with different resistance values into the circuit in turn, and then adjusting the sliding rheostat, the voltage can be controlled unchanged? (it is written in the book)
Isn't the voltage always the power supply voltage? How can different fixed value resistors have different voltages at both ends?

The voltage mentioned here is the voltage at both ends of the constant resistance, not the power supply voltage. By adjusting the sliding rheostat, the voltage at both ends of the constant resistance with different resistance values (measured by voltmeter) can be the same. Only when the voltage at both ends of the constant resistance is constant, can we explore the relationship between the resistance value of the constant resistance and the current passing through it (measured by ammeter),

Experiment on the relationship among current, voltage and resistance
When we let the constant resistance R be constant, we can get that u is proportional to I by moving the slide. But if we let u be constant, here u refers to the power supply voltage or the voltage at both ends of the constant resistance. At this time, we should change what to get the relationship between R and I,

Note the role of the sliding rheostat in this test
Verify that u and I are proportional, provided that R is a constant value. Here, the constant value resistor R is used to achieve. All the research is carried out around the constant value resistor R. in this case, the formula u = IR, u = two voltage of the constant value resistor, I = current of the constant value resistor. The sliding rheostat is used to adjust the current of the constant value resistor in this experiment. The resistance of the sliding resistor does not participate in the calculation
In the experiment of verifying that R is inversely proportional to I, the premise is that u is a constant value. Here u = power supply voltage. Resistance = constant value resistance + sliding rheostat resistance. Sliding rheostat plays a role in changing resistance value in this experiment. The formula should be I = u / (R + R)