つける
つける · tsukeru · JLPT N5 · verb-ichidan
to turn on
💡 tsukeru = tsuku (to be on, attached) + -eru: you make it be on
つく means a light comes on or something attaches by itself. Swap the ending to つける and you are the one doing it: you switch the light on, you attach the thing. Pair: 電気がつく (the light is on) vs 電気をつける (I turn the light on).