如图所示,电源电压不变,将定值电阻$R_{1}$和$R_{2}$串联后接在电源上,$R_{1}$消耗的功率为$3W$,$R_{2}$消耗的功率为$6W$,则$R_{1}$和$R_{2}$之比为______.若将它们并联后仍接在该电源上,则$R_{1}$和$R_{2}$消耗的功率之比为______.