Please explain STP Root Bridge Election process?

STP Root Bridge Election: In Spanning-tree Root Bridge is elected on the basis of bridge-id.

=>Initially all switches exchange BPDU( Bridge protocol Data Unit ) and in bpdu's they exchange bridge-id on the basis of that switches do Root Bridge Election.

=>Bridge-Id is of 8byte . Lower Bridge-Id is preffered

=> As you can see by default priority of all switches are same i.e 32768 so an election will be on the basis of mac - address of switches.

Election :

Sw1 will become Root Bridge because it have minimum Bridge-Id.