When you walk across a carpet during the winter you often get a shock when you touch a metal door knob. The reason is that you pick up electrons via friction between your feet and the carpet. If you pick up -40 μC of charge, how many electrons did you acquire?
Since the net charge that is gathered is negative, electrons are present in the person as he/she touches the metal door knob. These electrons will be collected until you discharge it by touching anything that will connect it to the ground. By doing so, you will feel certain shock since it is a form of releasing of energy.
One electron has a charge of -1.602x10^-19 C. So to determine the number of electrons acquired:
`-40 mu C * (1.0 x 10^-6 C)/(1 mu C) * (1 el ectron)/(-1.602 x 10^-19 C)`
`= 2.4969 x10^(14) = 2.5x10^(14) el ectrons`