How many electrons would have to be removed from a coin to leave it with a charge of #+1.6 xx 10^-7# C?
We assume that the coin has a net charge of zero. Recall that electrons have a negative charge, and specifically, they have a charge of
Thus, removing electrons from the coin would decrease its negative charge, i.e. increase its positive charge.
#+1.6xx10^(-7) cancel"C" xx "1 electron"/(-(-1.6xx10^(-19) cancel"C"))#
#= color(blue)(10^12 "electrons")#
The first negative sign indicates removal of the electron, and the second negative sign is part of its defined charge.