What is the purpose of 400Hz electricity?

The purpose of 400Hz electricity is primarily related to its widespread use in electronic systems, particularly in military and aviation applications. This frequency is advantageous because it allows for smaller transformers and motors, which can reduce weight and space consumption on aircraft and ships. Many critical electronic systems, such as fire control and sonar, operate at this frequency due to the need for efficient power supply and signal processing capabilities.

In contrast to other options, high voltage transmission does not typically operate at this frequency as lower frequencies—such as 60Hz or 50Hz—are standard for transmission lines. Lighting systems usually operate on direct current or at the standard power grid frequency. While some communication systems can work with varying frequencies, they often do not utilize 400Hz electricity as a primary power source. Therefore, the correct answer emphasizes the importance of this frequency in enabling various sophisticated electronic systems critical for operational capabilities.