Question

In hydrogen discharge tube, it is observed that through a given cross-section $3.13\times 10^{15}$ electrons are moving from right to left and $3.12\times 10^{15}$ protons are moving from left to right per second. The current in the discharge tube and its direction will be

• A. $1mA$ , towards left
• B. $2mA$ , towards right
• C. $1mA$ , towards right
• D. $2mA$ , towards left

Answer 1

Answer: (C)

Number of electrons $n_e=3.13\times 10^{15}$
Number of protons $n_p=3.12\times 10^{15}$
Now, the current is given by the relation
$i=n_e{q}_e+n_p{q}_p$
$=3.13\times 10^{15}\times 1.6\times 10^{-19}+3.12\times 10^{15}\times 1.6\times 10^{-19}$
$=1\times 10^{-3}=1mA$
Now, due to excess the charge on electrons, the direction of the current will be towards right.