Chapter 26, Problem 76P

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 toward the negative terminal. (a) What is the current in a hydrogen discharge tube in which 3.1 × 10¹⁸ electrons and 1.1 × 10¹⁸ protons move past a cross-sectional area of the tube each second? (b) Is the direction of the current density toward or away from the negative terminal?