As shown in the figure, during the movement of slide P of rheostat R0, the indication range of voltmeter is 0 ~ 4V, the indication range of ammeter is 1 ~ 0.5A, and the internal resistance of power supply can be ignored. Calculate the resistance value of resistance R, the maximum value of rheostat R0 and the electromotive force E of power supply

As shown in the figure, during the movement of slide P of rheostat R0, the indication range of voltmeter is 0 ~ 4V, the indication range of ammeter is 1 ~ 0.5A, and the internal resistance of power supply can be ignored. Calculate the resistance value of resistance R, the maximum value of rheostat R0 and the electromotive force E of power supply

When U1 = 0V, I1 = 1a, e = i1r = R ① When the voltage is U2 = 4V, the current is I2 = 0.5ar0 = u2i2 = 40.5 Ω = 8 Ω. The electromotive force of power supply is e = U2 + I2R = 4 + 0.5r ② According to the solution of (1) and (2), e = 8V, r = 8 Ω

When we measure resistance by voltammetry, when we move the slide, we find that the indication of ammeter becomes larger and the apparent number of voltmeter becomes smaller

When moving the slide, it is found that the indication of the ammeter becomes larger because the resistance is decreasing, so the current becomes larger. However, as the current becomes larger, the voltage drop on other resistors (if any), ammeter and internal resistance of the power supply begins to increase, making the voltage at both ends of the resistor smaller

When the slide P of rheostat moves between two points, the indication range of ammeter is from 1 A to 2.4 A, and that of voltmeter is from 7.2 V to 10 v
Then the resistance value and supply voltage of the fixed resistance R are ()

Formula: r = (u1-u2) / (i1-i2)
So r = (u1-u2) / (i1-i2) = (10v-7.2v) / (2.4a-1a) = 2 Ω