Hello,

 I've just bought yesterday a Dell 5110 i7 and i plug in the ac/dc adapter. it charges very good, but if i listen careful the adapter i hear a sound like an open circuit, like when you are holding in hand a power cable and you are so close to an object so we can see the electrical arc between objects. I dont know how to explain. The ideea is that the adapter works just fine but the sound is weird.