Eli5 Why chargers make high pitched noise when battery is full?
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Inside of your charger’s “block” is something called a transformer. Your phone isn’t designed to live on the kind of electricity that comes from the wall so it needs to be changed. You can think of the transformer as a sort of valve that changes the “speed” and “strength” of the electrical current flowing into your phone.
The electricity that comes out of the wall isn’t a steady flow, it’s more a wobbling/back and forth type energy. This wobbling happens between 50 and 60 wobbles per second. What this ends of meaning is part of that wobble energy can become physical, it can cause parts of the transformer to actually move or grown/shrink in a very tiny way, but still actually happening, 50 to 60 times per second. That physical movement is just like a speaker, it pushes air back and forth 50-60 times per second which means – sound.
What you’re hearing is something the 60-cycle hum. It’s the same physical *thing* that causes lightbulbs to flicker super quickly or guitar amplifiers to make a SHHHH sound when turned up loud.
If you’ve ever been in an electrical closet, like a large building might have, they also have transformers there but they are BIG, like refrigerator sized, and they are LOUD as heck. Same thing, just on a much, much larger scale.
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