Vaihtosähkön

Vaihtosähkö, often referred to as alternating current (AC) in English, is an electric current that periodically reverses its direction. This is in contrast to direct current (DC), where the flow of electric charge is only in one direction. The defining characteristic of AC is its sinusoidal waveform, meaning the voltage and current vary in a smooth, cyclical manner over time.

The generation of AC typically occurs in power plants using rotating generators. As the magnetic field or the coil rotates, it induces an alternating voltage and thus current. This alternating nature makes AC particularly well-suited for long-distance power transmission. Transformers can easily step AC voltage up for efficient transmission over power lines and then step it back down for safe use in homes and industries.

Commonly, AC power is supplied at a specific frequency, which is the number of cycles per second. In most of the world, this frequency is 50 Hertz (Hz), while North America primarily uses 60 Hz. This frequency determines how quickly the current changes direction. Most household appliances and electronic devices are designed to operate on AC power. Understanding the principles of AC is fundamental to electrical engineering and the functioning of modern electrical grids.