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 the electrons striking the target per second is

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

Answer 1

The correct option is A

$2\times {10}^{16}$

Given, Current through the X-ray tube, I =3.2 mA; Potential difference applied to the X-ray tube = 5 kV

Let 'n' be the number of electrons hitting the target and 't' be the total time the X-ray tube was in working condition.

We know that, $q=ne$, where, q= Total charge on a body, n= Number of electrons, e= Charge on an electron

Also, $I=q/t\Rightarrow q=It$
Therefore : $q=It=ne\Rightarrow \frac{n}{t}=\frac{I}{e}$

Hence, the number of the electrons striking the target per second is $=\frac{I}{e}=\frac{3.2\times {10}^{-3}}{-1.6\times {10}^{-19}}$
$=2\times {10}^{16}$......(We ignore the negative charge of an electron and only consider the magnitude to find the number of electrons)