How many electrons did the fly loose?-Got the answer please help explain how to get to it.

Question

A housefly walking across a surface may develop a significant electric charge through frictional charging. Suppose the fly picks up a charge of +87 pC. How many electrons did it lose to the surface as it is walking?

I got 5.4 which is the correct numbers for the first two digits, but I am confused how the answer is 5.40x10^8.

Answer 1

One electron has a charge of 1.602 x 10^-19 Coulombs, so we can write

1 e- / 1.602 x 10^-19 C. The units for this would be electrons per coulomb.

When you multiply this by the charge on the fly, you get 1 e- / 1602 x 10^-19 C x +87 x 10^12 C which is the number of electrons lost to the surface.

Carrying out the calculation on your calculator should give 5.4 x 10^8 electrons. You have to know that one picocoulomb (pc) is 1.0 x 10^-12 coulombs.