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
$i=n_{e}q_{e}+n_{p}q_{p}$
$=3.13\times 10^{15}\times 1.6\times 10^{- 19}+3.12\times 10^{15}\times 1.6\times 10^{- 19}$
$=1\times 10^{- 3}=1 \, mA$
Now, due to excess the charge on electrons, the direction of the current will be towards right.