But now, if I integrate the charge density over the entire region, then what I will get is actually the total amount of electric charge inside the region.

如果将电荷密度对整个区域做积分，将得到，在区域内的电量总和。

youdao

There is no realistic prospect for widespread electric air travel: the jet engines on aircraft need the high-energy density that only chemical fuels can provide.

广泛的以电力为驱动的空中旅行很不现实：飞机发动机需要高密度的能量，而这些只有化学燃料才可提供。

youdao

It is the electric charge density.

这是电荷密度。

youdao

So, instead of having the periodic variation of water, or the periodic variation of air density here we're talking about an electric field.

不像水或者空气密度的,周期变化，我们这里,讨论的是电场。

麻省理工公开课 - 化学原理课程节选

The electric current density possible with such windings is approximately 30 to 100 times greater than the values achievable with copper coils at room temperature.

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Plus, according to Andy Chu, vice president of marketing and communications at battery-maker A123, because hybrids do not rely solely on electric, they can afford to sacrifice some energy density and stick with the NiMH without fear of running out of juice.

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Bosch reckons that for electric cars to become universally popular, a threefold increase in energy density and a fall of two-thirds in the price of batteries will be needed.

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