Final answer:
Analyzing the electrical systems of aircraft, only essential buses would be powered by the battery in flight. The energy density limitations of current lithium-ion batteries would lead to restricted range and prolonged recharge times for electric planes.
Step-by-step explanation:
The topic of the question pertains to the electric systems of aircraft, specifically which buses are powered when an airplane is running on battery power in flight. In general aviation, essential buses are designed to be powered in order to maintain critical systems operational, assuming a single battery is providing the power. The exact buses that remain powered would depend on the airplane's design, but typically they would include those that support vital functions such as communication, navigation, and some flight instruments. Considering the comparison of power density in batteries versus liquid fossil fuels, it is clear that a purely battery-powered flight would significantly limit the range and operational capabilities of conventional aircraft, as modern batteries store significantly less energy per kilogram compared to traditional jet fuel.
Moreover, the feasibility of powering large passenger planes with batteries is currently not practical due to weight and energy density limitations. This is evidenced by the fact that current lithium-ion batteries have only about 5% of the energy per kilogram compared to liquid fossil fuels, and thus a full battery replacement would lead to a significantly reduced flight range and much longer recharge times.