Why is it safe to use two-pin plugs (Eg. Most mobile chargers) even upside down, when live and neutral wires are switched? How does the charging still work fine?
In: Engineering
When it comes to AC electricity, polarity is less important. You can actually rip the grounding pin out of most plugs and plug it in upside down and most devices should work; Although it can make things more dangerous, as this often times places the power switch at the end of the circuit, instead of at the start (This means the entire circuit is energized, but it just doesn’t have a ground yet).
In the case of DC powered electronics, most use switch-mode power supplies, which do not care about polarity. This includes phone chargers. If polarity matters to an electronic device, the manufacturers will use a polarized plug. In the US and Japan, the neutral blade of the plug will be larger, preventing people from plugging it in the wrong way.
Most of those devices have an AC to DC converted and unpolarized capacitors in their circuitry. Its like all the streets in the circuit are two way.
When you can’t reverse the plug (switch the polarity) it indicates the circuitry has some one way streets (polarized components–usually capacitors).
The difference in voltage between the wires powers your device, and as this difference reverses many times per second, it’s the same either way.
Only in case of an electrical fault (exposing the device’s energized components to an outside object or person) does it matter which is which.
Because all our plugs work with alternating current. The direction of flow is changing constantly.
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