题目

如图14-6-6所示，电源电动势为E，内电阻为r,R1、R2为定值电阻，R3为滑动变阻器.当R3的滑片P向右移动时，下列说法中正确的是（    ） 图14-6-6A.R1的功率必然减小                   B.R2的功率必然减小C.R3的功率必然增大                   D.电源消耗的功率必然减小 答案：解析：R3↑→R↑→I↓→U端↑→I1↑→I2↓，所以P1↑，P2↓,P↓.答案：BD --- Would like to to go to the concert with me tonight? --- I’d love to, but of us couple has tickets. Do you have some? A. both B.neither C. none D.each