Restriction enzymes question

So there's a question on a practice exam that basically asks that if you use EcoRV as an restriction endonuclease, and you create a recombinant plasmid vector with a plasmid that has one EcoRV site, how many bands appear when you perform PCR.

Then answer given is 2 bands, since it is basically cutting a strand of DNA into 2 strands. But this confused me because I thought plasmids were circular, so if you if you only have one restriction site, wouldn't you pretty much just open up the...

Restriction enzymes question