eli5: how does AC power provide power when it’s just shifting back and forth? Don’t you need to have current going in one direction
In: 67
Consider a bicycle with fixed gearing and no free-wheeling — or perhaps a kid’s tricycle. Whenever it’s moving, the pedals are going up and down. And imagine your feet are clipped in so you can both push and pull on the pedals. If you push downward while the pedal is moving down, and pull upward whe the pedal is moving up, you can supply energy and make the bike/trike move uphill. But if you push downward while the pedal is moving up, and pull upward while the pedal is moving down, you’re removing energy from the bike/trike, and can make it slow down, or descend a hill gradually.
The key is the timing of the push/pull compared to the pedal’s motion. Similarly with electricity the direction of power flow depends on how the timing of voltage polarity and current direction relate. When the voltage is positive, power flows in the direction the current is flowing toward; when the voltage is negative, power flows in the direction the current is flowing away from. With a simple resistive load like a light bulb, the current will always flow in the direction that allows the resistor to absorb power. This is analogous to connecting a saw blade to the bike pedals — it resists both the push and the pull, so its timing always takes energy from the pedal.
Latest Answers