Question

A current is established in a gas discharge tube when a sufficiently high potential difference is applied across the two electrodes in the tube. The gas ionizes; electrons move toward the positive terminal and singly charged positive ions move toward the negative terminal. What is the current in a hydrogen discharge tube in which 3.4 ✕ 1018 electrons and 1.4 ✕ 1018 protons move past a cross-sectional area of the tube each second? (Enter the magnitude.)

Answer 1

Explanation:

It is given that the number of electrons passing through the cross-sectional area in 1 s is $3.4 \times 10^{18}$. Also, we know that charge on an electron is $-1.60 \times 10^{-19} C$, then negative charge crossing to the left per second is  as follows.

         I- = $3.4 \times 10^{18} electrons \times -1.6 x 10^{-19} C/electrons$

         I- = 0.544 A

As it is given that the number of protons crossing per second is $1.4 \times 10^{18}$, as the charge on the proton is $+1.60 \times 10^{-19} C$, then positive charge crossing to the right per second is calculated as follows.

          I+ = $1.4 \times 10^{18} electrons \times 1.6 \times 10^{-19} electrons/C$

            I+ = 0.224 A

          I = l I+ l + l I- l

So,    I = 0.544 + 0.224

            = 0.768 A

Thus, we can conclude that the current in given hydrogen discharge tube is 0.768 A.