题目

现用直流电源给蓄电池充电，如图所示，若蓄电池内阻r，电压表读数U，电流表的读数为I。则蓄电池的发热功率为_________，电能转化为化学能的功率为_________。  答案：I2r，UI－I2r解析:略 —What should a goldfish be fed? Is candy OK?—No! It______be fed candy. Give it shrimp or cooked rice.A.doesn't have toB.may notC.needn’tD.can't