Direct Current (DC) is essential for the process of electrolysis. Electrolysis is the process of breaking down a compound using an electric current. The electric current causes ions to move, which results in a chemical reaction that breaks down the compound. In order for electrolysis to work, a direct current is required, as the ions must flow in one direction. Alternating Current (AC) changes direction and would not provide a consistent flow of ions.
Heating, lighting, and turning a motor can be done by either DC or AC. Heating can be done by passing an electric current through a heating element, which can be powered by either DC or AC. Lighting can be done by passing an electric current through a light bulb, which can be powered by either DC or AC. A motor can be powered by either DC or AC, but the type of motor and the application will determine which type of current is more suitable.