(1)R3与变阻器R2的并联电阻为R23= R2R3 R2+R3 = 12×6 12+6 Ω=4Ω由闭合电路欧姆定律得,通过电阻R1的电流为 I1= E R23+R1+r = 6 4+5+1 A=0.6A (2)通过电阻R3的电流为 I3= R2 R2+R3 I1=0.4(A) 电阻R3的电功率是PR3=I32R3=0.96(W)答:(1)通过电阻R1的电流是0.6A.(2)电阻R3的电功率是0.96W.