题目

Railway Stephen Manufacturer: Fisher Price Publication date: 2016-6-15 Price:＄9.65 For Ages: 2+ Stephen is one of the earliest engines ever built. Other engines may be faster and stronger than Stephen, but in terms of strength or speed, Stephen makes up for with his positive spirits, a sense of humor and knowledge. Stephen can connect to other engines and vehicles with magnet connectors. Monster Truck Manufacturer: LEGO Publication date: 2016-2-21 Price:＄29.95 For Ages: 3+ Get the big monster truck to the race with the Monster Truck! Check the engine and huge tires before the show. 某学生欲测一未知电阻的阻值，可供选择的器材有；电流表A1量程0～10mA电流表A2量程0～0.6A电压表V1，量程0～3v电压表V2量程0～l5V滑动变阻器一只，电源4.5V，电健2个．如图所示，当电键K2连a时．两电表的指针偏转角度都在满偏的4/5处，若将K2接b时，其中一个电表的指针偏角几乎不变，另一电表的指针偏转到满偏的3/4处．该学生所选用的电压表的量程为    ．所用电流表的量程为    ，该电阻的阻值为    ．