如图所示,ab两端电压U不变,若cd两端接理想电压表,则示数为60V,若cd两端接理想电流表,则示数为3A,若cd两端接电阻R3,则R1、R2、R3上消耗的电功率相等.电阻R1、R2、R3的阻值分别为_Ω,

问题描述:

如图所示,ab两端电压U不变,若cd两端接理想电压表,则示数为60V,若cd两端接理想电流表,则示数为3A,若cd两端接电阻R3,则R1、R2、R3上消耗的电功率相等.电阻R1、R2、R3的阻值分别为______Ω,______Ω,______Ω,a、b两端的电压为______V.

cd端接电压表时:I=U(R1+R2),IR2=UR2R1+R2=60V①;cd端接电流表时:R2短路,I′=UR1=3A②;cd端接R3,功率相等,R2和R3并联:U2=U3,由P=U2R可得R2=R3,I1=I2+I3=2I3=2I2,由题意知三个电阻消耗的功率相等,由P=I2R...