ATPL Airframe Practice Test

The electrolyte in a Nickel-Cadmium battery is potassium hydroxide. This alkaline solution serves as the medium through which electric charge is conducted within the battery. In Nickel-Cadmium batteries, the charge and discharge processes involve the transfer of ions between the positive and negative electrodes, which are made of nickels and cadmium, respectively. The potassium hydroxide solution facilitates this ionic movement, essential for the battery's functioning, providing both conductivity and stability during cycles of charge and discharge.

The other choices do not serve as electrolytes in Nickel-Cadmium batteries. Nickel dioxide is an electrode material rather than an electrolyte, potassium chloride is not suitable due to its insolubility in alkaline battery environments, and hydrogen peroxide is not used in such batteries as it does not provide effective ion transport required for the reactions that occur in Nickel-Cadmium systems.