Why do some laptops use aluminum chases and have motherboards sitting right next to them (with no insulation? can't remember)

[CaptainPlanet]

Even in laptops that use plastic chasis, the inside of the casing still has thin metal plates surrounding the circuit boards.
Wouldn't there be danger of short circuiting if the pieces touch?

 

I have also seen some harddrives with the circuit boards right at the bottom with no protrusion to prevent circuit contacting with metal surfaces, and it's sold inside a metal enclosure with no further shielding whatsoever. I don't understand this design at all.

[Stormseeker9]

16 minutes ago, CaptainPlanet said:

Even in laptops that use plastic chasis, the inside of the casing still has thin metal plates surrounding the circuit boards.
Wouldn't there be danger of short circuiting if the pieces touch?

 

I have also seen some harddrives with the circuit boards right at the bottom with no protrusion to prevent circuit contacting with metal surfaces, and it's sold inside a metal enclosure with no further shielding whatsoever. I don't understand this design at all.

Well.. they use aluminium, not metal in many cases. 

[GoldenLag]

um, not really. keep in mind that a lot of the motherboard is in contact with anything and there is an aluminium oxide coating which isnt conducting.