Question

The potential difference applied to an X-ray tube is 5 kV and the current through it is 3.2 mA. Then the number of electrons striking the target per second is

• A. $5\times 10^6$
• B. $2\times 10^{16}$
• C. $1\times 10^{17}$
• D. $4\times 10^{18}$

Answer 1

Answer: (B)

Given, potential difference, $V=5kV$ and discharge current, $I=3.2mA=3.2\times 10.3A$
As, We know that current, $I=\frac{ne}{t}$
where, $n=$ number of electron, $e=$ charge on electron and $t=$time
$\Rightarrow n=\frac{It}{e}$
Putting $t=1s$ and $e=1.6\times 10^{-19}C$
$\Rightarrow n=\frac{3.2\times 10^{-3}\times 1}{1.6\times 10^{-19}}=2\times 10^{16}$
Hence, $2\times 10^{16}$ electrons are striking the target per second.