Electric power plants typically use alternating current to generate electricity. AC power can be easily raised and lowered through transformers for long-distance power transmission in the power grid...

Some aircraft and ship systems use direct current. For example, flight instruments and avionics equipment on airplanes, as well as navigation systems and communication equipment on ships, all use direct current.

Communication system: AC power is used to supply power to communication facilities such as telecommunications base stations, communication network equipment, and telephone systems.

Some specific industrial applications require direct current. For example, electroplating, electrolysis processes, arc welding, electrolytic aluminum production, etc. All require direct current to achieve specific chemical or physical reactions.

Medical equipment: Many medical devices, such as X-ray machines, nuclear magnetic resonance machines, ultrasound equipment, etc., use AC power supply.