Therefore, the answer is that the voltage across the control conductor is constant.
(2) Analyze and compare the relationship between the current and the voltage of the experimental serial number 1, 2, 3, or 4, 5, 6. When the resistance value is constant, the voltage increases several times and the current increases several times accordingly, so the current passing through the same conductor is proportional to the voltage at both ends of the conductor;
So the answer is that the current through the same conductor is proportional to the voltage across the conductor.
(3) By analyzing and comparing the relevant data of the experimental serial numbers 7, 8 and 9, it is found that when the voltage is constant, the resistance increases several times and the current becomes a fraction of the original, so when the voltage at both ends of the conductor is the same, the current passing through the conductor is inversely proportional to the resistance of the conductor;
So the answer is: when the voltage across the conductor is the same, the current through the conductor is inversely proportional to the resistance of the conductor.
(4)① Further analysis and comparison table 1 or table 2 shows that the ratio of the voltage across the same conductor to the passing current is the same;
② By further analyzing and comparing Table 1 and Table 2, it can be found that for different conductors, the ratio of voltage at both ends to current is different, and the greater the ratio, the greater the resistance.
Therefore, the answer is: the ratio of the voltage at both ends to the current through the same conductor is the same; For different conductors, the ratio of voltage to current at both ends is different, and the greater the ratio, the greater the resistance.