There is no realistic prospect for widespread electric air travel: the jet engines on aircraft need the high-energydensity 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。
2
Capacitance of conductor capacitor electric field energy and energy density.
导体的电容；电容器。电场的能量和能量密度。
3
Week 16 Energy of point charges system, energy of electric field in capacitor , energy and its density of electric field.