Question

A person scuffing her feet on a wool rug on a dry day accumulates a net charge of -52 µc. how many excess electrons does this person get? electrons by how much does her mass increase?

Answer 1

Using q=1.60217662 E-19 C we get:
$\frac{52 \times 10^-^6}{1.60217662 \times 10^-^1^9}=3.24558 \times 10^1^4 electrons$
Then using 9.10938356E-31 kg as the mass, we get
 $(3.24558 \times 10^1^4)(9.10938356\times 10^-^3^1)=2.95653\times 10^-^1^6kg$

Answer 2

As per the question  the person is scuffing his feet under a wool rug on a dry day.

As the electron affinity of the wool is less as compared to human body ,so some amount of electron will be transferred from wool to the feet of the person.

The total amount of charge that is accumulated on his feet is -52 micro coulomb.

we are asked to calculate the net amount of excess electrons .

whenever a body gets negative charge ,an integral amount of electronic charge is transferred  to the body.

Hence total charge=number of electrons ×one electronic charge

                         i.e  q=ne

Here n= total number of electrons and e is the charge of one electron

we know that $e= -1.602*10^{-19} coulomb$

The total charge q= -52 micro coulomb i.e $-52*10^{-6} coulomb$

So total number of electrons $n=\frac{q}{e}$

                                                       =  $\frac{-52*10^{-6}coulomb }{-1.602*10^{-19}coulomb }$

                                                   $=32.459*10^{13}$

                                                        i.e 32×10^13 electrons approximately.

The mass of one electron is $9.1*10^{-31} kg$

Total mass increased by the main will be equal to the total mass of excess electrons.

Hence mass increment=$m_{e} *32*10^{13}$

                                     =$9.1*10^{-31} *32*10^{13} kg$

                                     =$291.2*10^{-18} kg$