HOw many electrons make up a charge of -30 micro coulombs???

Answer 1

a micro is 10^-6 or one millionth
so we are talking about -30 *10^-6 coulombs

the charge on the electron is -1.6 *10^-19 Coulombs

so N electrons * (-1.6*10^-19 coulombs/1 electron) = -30 *10^-6 coulombs

so N = 30 *10^-6 /1.6*10^-19

that is (30/1.6) * 10^13
which is (3/1.6) *10^14
which is 1.875 * 10^14 electrons