看你这题应该是并联吧！R1与A1串联再与R2并联，电流表A在干路上。解：R1两端的电压：U1=I1R1=1A×5Ω=5V，∵R1、R2并联∴U2=U1=5V，I2=I-I1=1.5A-1A=0.5A，∴R2的阻值：R2=U2/I2=5V/0.5A=10Ω．
