Transcript & Summary: AD - Why do I get this spark when I unplug my hair dryer?

[00:00] Have you ever noticed if you unplug an appliance while it's running like this hair dryer, then you get a spark? To make a 1 cm spark in air requires 10,000 volts, but main's voltage is only around 120 to 240 volts. So, where is that extra voltage coming from? Thanks to Anker for sponsoring this video. When the haird dryer is on, current flows through these coils of wire, but that current also creates a magnetic field. And so when you pull out the plug, you are cutting off that current suddenly, which means the magnetic field will [00:33] rapidly drop to zero. But nature hates a sudden change in magnetic field. So it tries to compensate. As the magnetic field drops, it induces a voltage in the coil to try to maintain that current. And that voltage can get so high it ionizes the air between the plug and the socket. That is the spark that we see. But this same effect can actually be quite useful because the purpose of a charger, a wall charger, is to take high voltage mains electricity and convert it into smooth low voltage DC for like your [01:04] phone or your laptop. And to achieve that, the current in this device is switched on and off hundreds of thousands of times per second using transistors that creates all these little pulses of electricity. Now, to smooth those out, you require an inductor, a coil of wire just like in the hairdryer, just with a very specific design. Now this inductor resists sudden changes in current. It acts like a shock absorber. So when the current rises it stores energy in a magnetic field and then when the current falls it releases [01:30] that energy again helping to turn choppy electrical pulses into steady DC. Now there is a trade-off which is the higher the voltage the inductor has to handle the bigger it needs to be which is why high power charges need really large inductors. But Anker has redesigned the circuitry in their fast chargers using a technique called embuck combined with their custombuilt algorithm. So instead of doing one large voltage drop across a single inductor, Embuk splits the conversion across multiple levels and [02:00] switches it up to 200,000 times per second. That means the inductor has less energy to handle for every switch cycle. So the inductors can be shrunk to a quarter of the standard size. That is what allows Anker to pack 160 Ws of fast charging into a body this compact.