Question

a 100mg body was initially neutral after it underwent a process and acquired -2c of charge calculate percentage change in mass of body

Answer 1

Given :

Initial mass of the body = 100 mg

Charge acquired by the body = - 2 C

To Find :

Percentage change in mass of the body = ?

Solution :

Since we know that charge on 1 $e^-$ is = $1.6 \times 10^{-19}$

So when -2 C of charge is given to the body , the total no. of electrons added to the body will be :

$= \frac{2}{1.6\times 10^{-19} }$

$= 1,25 \times 10^{-19} e^-$

∴ Mass of one $e^- = 9.1\times 10^{-31}kg$

So , mass of $1.25 \times 10^{19} e^-$ = $1.25 \times 10^{19} \times 9.1\times 10^{-31}kg$

                                          $=11.375 \times 10^{-44} mg$

So , change in mass is  $=11.375 \times 10^{-44} mg$

Hence %age change in mass = $\frac{\Delta mass}{initial mass}\times 100$

                                                $= \frac{11.375 \times 10^{-44}}{100}\times 100$

                                               $=11.375 \times 10^{-44}$ %

So, the percentage change in mass of body is $11.375 \times 10^{-44}$ %