Open position guitar power chords contain at least one open string and therefore
can only be played in one place.
The root of this power chord is E, the open 6th string.
Barre your first finger across the 5th and 4th string. Be
careful not to barre the 3rd string or this will not be a
power chord.
The root of this power chord is A, the open 5th string.
The root of this power chord is D, the open 4th string.
For the fingering think of a D chord minus your 2nd finger.