Why does my Android device generate more heat on an AC charger? My Huawei IDEOS u8150 is new and ever since I used the AC charger that was supplied with it, my device gets a bit hotter (a noticable 5 degrees Celsius extra compared to charging via USB from laptop). 

Why is it not that hot when I try to charge it through PC/laptop?

I hear a whirring noise from the AC charger always and the adapter gets a little warm too.

Also, my device charges faster on the AC charger compared to the laptop charge method. Is this normal on all devices in general? Or all Huawei devices? Or is this something faulty I should worry about?
I'm not an electrical engineer, but I'm pretty sure there's either


more current flowing through a wall charger than there would be a USB charger or...
the same amount of current which is just flowing faster from the wall than from the USB port


which is why the wall charger will fully charge your battery faster.  That heat is totally normal and nothing to worry about (unless it gets hot enough to burn skin, then I'd recommend not touching it).