In one second $10^{9}$ electrons move out of the body. Therefore the charge given out in one second is $1.6 \times 10^{-19} \times 10^{9} \,C =1.6 \times 10^{-10} \,C$

The time required to accumulate a charge of $1 \,C$ can then be estimated. to be $1\, C \div\left(1.6 \times 10^{-10} \,C / s \right)=6.25 \times 10^{9} \,s =6.25 \times 10^{9} \div(365 \times 24 \times$ $3600$ $years$ $=198$ $years$. 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.ns.