A direction, or a rhythm
DC flows in one direction; AC reverses direction periodically. The shape and frequency matter to equipment.
In 30 seconds
- A battery is a familiar DC source.
- Frequency counts cycles per second in hertz.
- Equal voltage numbers do not make AC and DC interchangeable.
Make it concrete
Draw a horizontal line and a wave that crosses zero. Label them ideal DC and sinusoidal AC. These are learning shapes, not measurements of a live circuit.
Change a value. Watch the relationship.
Ideal sinusoidal AC: v = Vpeak sin(2πft). Vpeak = 12 V. 1 screen second = 0.02 electrical seconds; waveform is slowed for viewing. The horizontal line is 12 V DC.
Check your understanding
Can an AC input rating alone prove that a device accepts the same DC voltage?
- A battery is a familiar DC source.
- Frequency counts cycles per second in hertz.
- Equal voltage numbers do not make AC and DC interchangeable.
Go to the source
Sources reviewed: 13.09.2026