The light bulb transfers electrical energy into light. what is one type of energy that is also generated that is not a desired effect?
a)
chemical
b)
heat
c)
mechanical
d)
sound

Light bulbs get hot !

The heat is not a desired effect, and the light bulb is not very efficient,
if you selected a light bulb to serve as a source of light.  But if chose a
light bulb to use in a place where you need heat, then the heat you get
from it is very desirable, and the light bulb is very efficient.  It all depends
on your point of view.