Question

A beam of electrons has an energy of $1joule$. How many electrons are in the beam? [$1eV=1.6x{10}^{-19}J$]

Answer 1

Step 1: Given data:

Energy = $1joule$

$1eV=1.6x{10}^{-19}J$

Step 2: To find no. of electrons,

Let there are n electrons in a beam moved by the potential difference of $1\text{volt}$.

The energy of n electrons = $1joule$

Formula used: $Energy=workdone$

Work done by $1$ electron = $qV$

Work done by n electrons = n$qV$ $=n(1.6\times {10}^{-19})\left(1\right)$

$1joule$$=n(1.6\times {10}^{-19})\left(1\right)$

No. of electrons =$\frac{1}{1.6\times {10}^{-19}}$$=6.25\times {10}^{18}$electrons.

Thus, there are $=6.25\times {10}^{18}$electrons in the beam.