Cool.. guitarists rock !!
they could ask on the theory on sound production on a guitar. vibration of strings from physics perspective.
f=(1/2L) sq.rt(T/u)
where f=frequency of vibration
L=effective length of string
T=tension in the string (approx. abt 6kg per string on an electric guitar)
u= linear density of string (max for low E n min for high E)
they could ask on fundamental frequency n harmonics
basically when we paly a note, the string vibrates in several frequencies. the sound we here corresponds to the fundamental frequency which is the loudest when played normally.
they sould ask how to make other frequencies louder..
ans would be harmonics. natural as well as artificial harmonics. we could explain how to play them..
then basic questions like types of guitar.
acoustic n electric guitar. theory behind both.. acoustic based on reverberation.. electric guitar on electromagnetic induction.
from here they could move to electronics/ electrical engineering. electronics? oh.. yeah.. i'm on..