题目

如图18所示电路中定值电阻R1=5Ω，R2为滑动变阻器，电源电压保持不变。当滑片在a端时，电流表示数为0.6A。滑片在b端时电压表示数为2V。 求：（1）电源电压；   （2）滑动变阻器R2的最大阻值。        答案：解：（1）当滑片在a端时，U1= U= IR1=0.6 A×5Ω=3 V    （2）当滑片在b端时，电流相等。 I2= I1= U1／R1=（U –U2）／R1=（3V—2 V）／5Ω=0.2 A R2= U2／I2=2 V／0.2 A =10Ω  You should not have said that to her. It hurt her. --- I know. I regret ___________. A．to have done that B．to do that C．having done that D．I have done that