∵P= U2 R ,∴灯泡电阻:R甲= U P甲 = (6V)2 3W =12Ω,R乙= U P乙 = (6V)2 6W =6Ω,两灯泡串联时电路电流:I= U R甲+R乙 = 6V 12Ω+6Ω = 1 3 A,P2=I2R乙=( 1 3 A)2×6Ω≈0.67W,灯泡并联在6V电路中,灯泡乙正常发光,此时灯泡功率:P3=3W,则P2小于P3;故选C.