## photo voltaic cell Vs. solar heating panel

1. The problem statement, all variables and given/known data

i've been asked to compare the efficiency of a photo voltaic cell and a solar heating cell (an array of pipes). both will be exposed to a 150W bulb for an equal amount of time.

2. Relevant equations

for photo cell: P=IV

for heating panel: P=fcT f=flow rate c=specific heat capacity T=change in temp

3. The attempt at a solution

im trying to say that both will have the same surface area exposed to the light, i was just wondering what measurement to use for the pipes: the surface area of the pipes that is exposed, or the area of the whole panel??

any other suggestions would be welcome :D

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 Recognitions: Homework Help Science Advisor I wouldn't worry about the actual surface area of the pipe. You are comparing a practical installation so the only consideration is the total floor (or roof!) area available for installation. Using a tugsten light bulb isn't a good model for the sun, it lacks the shorter wavelength blue and UV light that the solar panel is sensitive to. Can't you put both outside at the same time pointing in the same direction? That would also allow you to compare their relative efficency at best - sun pointing directly at them, vs worst - sun on horizon.
 yeah, i guess youre right, if im comparing the panels i should just use the area. we've been told to use a lightbulb, i know the actual sun would deliver a more useful result, but the bulb is what we're given. now that im thinking about it, im not quite sure what to use as the independent variable. would the different panels be enough?