A small drop of water, measuring 0.011 mm in diameter, hangs suspended above the ground due to the Earth’s electric field (see Problem 86). How many extra electrons are on the drop of water?

Data From Problem 86.

Charged planet. Lightning is striking somewhere on the planet at all times of the day. This and other meteorological phenomena produce a sustained vertical electric field—pointing downward toward the center of the Earth—that averages about 140 N/C near the surface. What is the average net charge per unit area on the Earth’s surface?