Adding a heatsink to an IC (Electronics Project)

[Scarletpimpofnel]

I'm making a project with a 7805 voltage regulator which I'll add a heatsink to, see image below to show the parts I'm using (+ some heat sink grease stuff to exclude air from the thermal surfaces).

A few questions:
1 - Is the metal back plate of the 7805 regulator actually at ground potential? I believe it is.
2 - If it is at earth potential do I actually need the polythene "patch" to put between the 7805 and the heatsink if the heatsink won't come into contact with anything live?

Thanks

[JoshSm]

Backplate is ground.

You can add the full set of bits if you want, if you skip the screw spacer it might affect the fit. The rectangular thing is usually TIM not an insulator.

[Scarletpimpofnel]

JoshSm said:

Backplate is ground.

You can add the full set of bits if you want, if you skip the screw spacer it might affect the fit. The rectangular thing is usually TIM not an insulator.

Right thanks for that. So if that rectangular patch is TIM then do I need to add additional paste?