Question

The total electric charge on a certain number of electrons is found to be $96368C$. What is the mass of these excess electrons?

• A. $0.5kg$
• B. $50g$
• C. $0.55mg$
• D. $5mg$

Answer 1

The correct option is C $0.55mg$

Given that total charge $\left(Q\right)$ on certain number of electrons is $=96368C$

We have to find the mass of these electrons.

So, we use the formula $Q=ne$

where $Q=$ charge; $n=$ number fo electrons;

$e=$ charge on $1$ electron $=1.6\times {10}^{-19}C$

So, number of electrons $n=\frac{Q}{e}=\frac{96368}{1.6\times {10}^{-19}}$

$=60230\times {10}^{19}$

$m=$ mass of $n$ electrons $=60230\times {10}^{19}\times$ mass of $1$ electron

Mass of $1$ electron $=9.11\times {10}^{-31}Kg$

So, $m=60230\times {10}^{19}\times 9.11\times {10}^{-31}Kg$

$=548695.3\times {10}^{-12}Kg$

$=0.55\times {10}^{-6}Kg$

$=0.55\times {10}^{-6}\times {10}^{6}mg$

$=0.55mg$