题目:用伏安法测未知电阻(约6欧左右)的阻值,实验桌上备有以下规格的器材:电流表一个(量程0～0.6安,0～3安)、电压表一个(量程0～3伏,0～15伏)‘,干电池三节(串联)、滑动变阻器(阻值为0～12欧)、开关、导线、被测电阻 R_X.(1)画出实验电路图,并在图上标出电流表、电压表的“+”、“-”接线柱.(2)该电路中,电流可变化的范围是 Title: Using voltammetry to measure the resistance of an unknown resistor (approximately 6 ohms), the following specifications are provided on the laboratory table: one ammeter (ranging 0 to 0.6 amps, 0 to 3 amps), one voltmeter (range 0 ～3V, 0～15V)’, dry cell three sections (series), sliding rheostat (resistance 0～12 ohms), switch, wire, measured resistance R_X. (1) draw the experimental circuit diagram, and in the figure Mark the “+” and “-” terminals of the ammeter and voltmeter. (2) In this circuit, the current can be changed