两定值电阻丝R1=440Ω,R2=220Ω,若将R1和R2串联后接到220V的电源上,在相同时间内,R1和R2上产生的热量之比是______________.
2:1
When he was asked about the question where he was last night, he was ______. [ ]
A. at loss
B. in a loss
C. at a loss
D. with losses
爆炸危险区域是指油品蒸气、液化石油气或压缩天然气与空气混合后,有可能达到()的区域。
A、燃烧极限
B、饱和
C、高压
D、爆炸极限