题目1 (98年甘肃中考题)如图1所示的电路中,用电器的电阻 R=50欧,要求通过它的电流能在60～600毫安范围内变化.(1)所选用的电源电压最少应为多少?(2)若所选用电源的电压为36伏,则变阻器 R_0的阻值变化范围是多少?分解分析所需电源电压最小值可分解为:①对于给定的电路,电流确定(60～600毫安),据 U=IR,当电路中电阻最小时,所需电 Question 1 (98 Gansu exam questions) In the circuit shown in Figure 1, the electrical resistance of the appliance is R = 50 ohms and the current through it is required to be varied within a range of 60 to 600 milliamperes. (1) Selected power supply What is the minimum voltage? (2) If the voltage of the selected power supply is 36V, what is the resistance variation range of R_0? The minimum value of the required supply voltage can be decomposed into: 1 For a given circuit, the current Determined (60 ~ 600 mA), according to U = IR, when the resistance in the circuit is the minimum, the required electricity