You Do Need power plug adapter while traveling from Northern Ireland to Balearic Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Balearic Islands are C and F and in Northern Ireland is G. This is how they look like.

Northern Ireland

In Northern Ireland, outlets of type G are in use.

Type G

Balearic Islands

In Balearic Islands, outlets of type C and F are in use.

Type C

Type F