The function of constant resistance in circuit It is said in the book that the constant value resistance remains unchanged, and the relationship between voltage and current is measured. Then a constant value resistance (such as 5 Ohm) is selected and measured. My question comes. ① in the circuit diagram, the constant value resistance is connected in series, and the voltmeter is connected in parallel with the constant value resistance, but how to explain the constant value resistance when measuring the current? ② the constant value resistance is connected in series to the circuit, Is the resistance in the circuit the same as the constant resistance? ③ since the resistance is the physical quantity that hinders the current, why is the value of the ammeter after the constant resistance the same as that of the ammeter placed in the constant resistance when the current passes through the constant resistance I don't have a good head

The function of constant resistance in circuit It is said in the book that the constant value resistance remains unchanged, and the relationship between voltage and current is measured. Then a constant value resistance (such as 5 Ohm) is selected and measured. My question comes. ① in the circuit diagram, the constant value resistance is connected in series, and the voltmeter is connected in parallel with the constant value resistance, but how to explain the constant value resistance when measuring the current? ② the constant value resistance is connected in series to the circuit, Is the resistance in the circuit the same as the constant resistance? ③ since the resistance is the physical quantity that hinders the current, why is the value of the ammeter after the constant resistance the same as that of the ammeter placed in the constant resistance when the current passes through the constant resistance I don't have a good head

1. R = u / I, the relationship between u and I can be obtained by keeping r unchanged
2. If the power supply has internal resistance, the resistance value of ammeter is large, and the resistance value of voltmeter is small, it is not the same as the constant resistance, so there are errors in the experiment
3. It's like a current. It flows the same way

Why use sliding rheostat? Can we measure current and voltage directly and measure resistance by voltammetry

Sliding rheostat has two functions in voltammetry
1 is the protection circuit
2 is to change the resistance of the circuit. If there are several more values, the resistance can be obtained by equations