What approximations did you have to make to predict the electron currents?
1)batteries always output approximately the same amount of current, no matter what is attached to them. 2)the temperature of the bulb filaments didn't change enough to make a significant change in the electron mobility.
3)the potential differences along the connecting wires were negligible.
4)the battery always maintained the same potential difference across itself.

power out to power in less than 100%

i will answer your question if you answer mine

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.