Why can't u = IR be used to judge that when the current is constant, the higher the voltage, the smaller the resistance (I don't know the resistance)

Why can't u = IR be used to judge that when the current is constant, the higher the voltage, the smaller the resistance (I don't know the resistance)

If you want to keep the current constant and increase the voltage, you have to reduce the resistance

According to the formula u = IR, when the current is constant, the voltage at both ends of the conductor is proportional to the resistance of the conductor?

Ideally, it would be
But the formula is I = u / R, which is generally determined by the voltage resistance

The relationship between current and voltage in circuit
Is the reduced voltage equal to the reduced current multiplied by the original resistance?

If it is true in a pure resistance circuit, it is not true in a circuit with capacitance and reactance. Because there is reactive power, it can not be simply understood as whether the reduced voltage is equal to the reduced current multiplied by the original resistance value

In superconducting state, the resistance R of conductor=______ Ω．

In some special materials, when the temperature drops to a certain value, the resistance value suddenly becomes zero, which is called superconductivity