The electrolyte of a nickel-cadmium battery is at its lowest when the battery is in which state?

• A. During discharge
• B. Fully charged
• C. Resting after use
• D. Freshly charged

Answer: (A)

In a nickel–cadmium cell, the electrolyte is an alkaline solution that carries ions between the electrodes. During discharge, the active materials at the electrodes are converted into their hydroxide forms, and this process effectively ties up dissolved electrolyte ions as solid hydroxides at the electrode surfaces. As more discharge happens, more of the electrolyte components become part of those solid products, so the concentration of free electrolyte in the solution drops. That’s why the electrolyte is at its lowest during discharge. When the cell is charged, the reactions are reversed and water and ions are returned to the solution, restoring the electrolyte concentration. Resting simply lets the cell approach equilibrium without producing or consuming significant additional electrolyte.