Question

The power of an X-ray tube is $16W$. If the potential difference applied across the tube is $5kV$, then the number of electrons striking the target per second is

• A. $8.4\times {10}^{16}$
• B. $5\times {10}^{17}$
• C. $2\times {10}^{16}$
• D. $2\times {10}^{19}$

Answer 1

Answer: (C)

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

16W in one second is 16J.
PD across tube is 5kV.
Energy of one electron accelerated across this potential is
$eV=1.6\ast {10}^{-19}\ast 5\ast {10}^3=8\ast {10}^{-16}J$
No of electrons per second is :

$\frac{16}{8\ast {10}^{-16}}=2\ast {10}^{16}$ electrons.