If `10^(9)` electrons move out of a body to another body evergy second, how much time is required to get a total charge of 1 C on the other body?

Explanation

In one second `10^(9)` electrons move out of the body. Therefore the charge given out in one second is `1.6xx10^(-19)xx10^(9)C=1.6xx10^(-10) C`. The time required to accumulate a charge of 1 C can then be astimated to be `1 C div (1.6xx10^(-10) C//s)=6.25xx10^(9)s=6.25xx10^(9) div (365xx24xx3600)` years = 198 years. Thus to collect a charge of one coulomb, from a body from which `10^(9)` electrons move out every second, we will need approximately 200 years. One coulomb is, therefore, a very large unit for many practical purposes.
It is, however, also important to know what is roughly the number of electrons contained in a piece of one cubic centimetre of a material. A cubic piece of copper of side 1 cm contains about `2.5xx10^(24)` electrons.