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某班组进行碎煤机轴承加热，采用方法是油煮法，已知油的比热C＝3.7kg·℃，油槽中有油50kg，当用电加热器把油从20℃提高到100℃时，此电加热器管规格为220V/1500W，共用4只，试求加热一次所用的时间（不计热能损耗及电压影响）？
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【单选题】Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-...
A.
do not use naturally produced fertilisers
B.
produce carbon dioxide when removing weeds
C.
use high doses of weed-killer
D.
use too many resources to qualify for organic status
【单选题】Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-...
A.
they are approved by many experts
B.
C. they won’t cause diseases
C.
B. they taste better than standard foods
D.
they are free from pesticides
【判断题】[判断题]钎焊是利用某些熔点低于母材的金属作为钎料,将焊件和钎料加热到高于钎料熔点,但低于母材熔点的温度,利用液态钎料湿润母材,填充接头间隙并与母材相互扩散实现连接焊件的方法。
A.
正确
B.
错误
【单选题】变压器器身检修时，器身温度应不低于周围环境温度，否则应采取对器身加热措施，如采用真空滤油机循环加热，使器身温度高于周围空气温度（）℃以上。
A.
3
B.
4
C.
5
D.
6
【单选题】下列实验不能获得成功的是( ) 1 用甲烷气体通入溴水制 溴 甲烷 2 甲烷和 氯气 混合光照制取纯净的一 氯 甲烷 3 用洒精灯加热甲烷气体制取炭黑和氢气
A.
只有 ①
B.
只有 ③
C.
只有 ②
D.
①②③
相关题目：
【单选题】Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-...
A.
do not use naturally produced fertilisers
B.
produce carbon dioxide when removing weeds
C.
use high doses of weed-killer
D.
use too many resources to qualify for organic status
【单选题】Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-...
A.
they are approved by many experts
B.
C. they won’t cause diseases
C.
B. they taste better than standard foods
D.
they are free from pesticides
【判断题】[判断题]钎焊是利用某些熔点低于母材的金属作为钎料,将焊件和钎料加热到高于钎料熔点,但低于母材熔点的温度,利用液态钎料湿润母材,填充接头间隙并与母材相互扩散实现连接焊件的方法。
A.
正确
B.
错误
【单选题】变压器器身检修时，器身温度应不低于周围环境温度，否则应采取对器身加热措施，如采用真空滤油机循环加热，使器身温度高于周围空气温度（）℃以上。
A.
3
B.
4
C.
5
D.
6
【单选题】下列实验不能获得成功的是( ) 1 用甲烷气体通入溴水制 溴 甲烷 2 甲烷和 氯气 混合光照制取纯净的一 氯 甲烷 3 用洒精灯加热甲烷气体制取炭黑和氢气
A.
只有 ①
B.
只有 ③
C.
只有 ②
D.
①②③
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