A gas discharge tube contains helium-4 ions (He2+\text{He}^{2+}He2+) and electrons (e−\text{e}^{-}e−) moving under the influence of an electric field, as shown in the diagram.
At a particular cross-section of the tube:
- 3.0 × 1015 helium-4 ions pass to the right per second.
- 5.0 × 1015 electrons pass to the left per second.
What is the magnitude and direction of the total electric current across this cross-section?
Take the elementary charge to be e=1.60×10−19 Ce = 1.60 \times 10^{-19}\text{ C}e=1.60×10−19 C.
0.16 mA0.16\text{ mA}0.16 mA to the right
1.28 mA1.28\text{ mA}1.28 mA to the right
1.76 mA1.76\text{ mA}1.76 mA to the left
1.76 mA1.76\text{ mA}1.76 mA to the right