I was doing homework, and the following appeared as a question:
A negatively charged thundercloud above Earth's surface may be modeled by a parallel plate capacitor. The lower plate of the capacitor is the Earth's surface and the upper plate is the base of the thundercloud.
After being asked to find things like capacitance and total energy, the last question is,
State one assumption that needs to be made so that the Earth-Thundercloud system may be modeled by a parallel plate capacitor
The answer I wrote was, "There is no energy lost as heat during the discharge"
My instructor marked this as incorrect. Isn't some energy lost in the creation of plasma, or during the friction at which the lightning is created?
Thank you for your help.