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【单选题】
防腐剂的作用对象是( )A.
食品
B.
微生物
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皮皮学刷刷变学霸
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【简答题】为 实现均匀梯度的磁场,两块相同的磁铁(磁铁截面积及表面感应强度相同)相对位置,即N极与N极相对,两磁铁之间留一等间距间隙,霍尔元件平行于磁铁放在该间隙的中轴上。间隙大小要根据测量范围和测量灵敏度要求而定,间隙越小,磁场梯度就越大,灵敏度就 ( )
【简答题】According to the author, what is the central truth that tech executives should acknowledge if they want the tech world to move in the right direction?
【单选题】负序（逆序）继电器用于______，其作用是______。A．短路保护／保护发电机B．过载保护／保护电网C．逆功率保护／保护电网D．逆相序和断相保护／保护电网负载
A.
短路保护／保护发电机
B.
过载保护／保护电网
C.
逆功率保护／保护电网
D.
逆相序和断相保护／保护电网负载
【简答题】High-tech machines have made life easier for millions around the world．However, some people still prefer low-tech ways of doing things．Here’s an example of why this is happening．You can microwave a fr...
【简答题】阅读理解。 High-tech machines have made life easier for millions around the world. However, some people still prefer low-tech ways of doing things. Here's an example of why this is happening. You can micro...
【简答题】High-tech machines have made life easier for millions around the world. However, some people still prefer low-tech ways of doing things. Here’s an example of why this is happening. You can microwave a...
【单选题】如图所示 , 一有限范围的匀强磁场 , 宽度为 d , 将一边长为 l 的正方形导线框以速度 v 向右匀速地通过磁场区域 , 若 d > l , 则导线框中不产生感应电流的时间应等于 ( )
A.
d/v
B.
L/V
C.
(d-L)/v
D.
(d-2l)/v
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