1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: What is the power of this bulb

  1. Jan 12, 2013 #1
    1. The problem statement, all variables and given/known data

    See attachment
    The question asks to calculate the brightness of the bulbs(g and h) in this new configuration.

    2. Relevant equations

    Since brightness [itex]\propto[/itex] Power

    P= [itex]V^{2}[/itex]/R
    P= [itex]I^{2}[/itex]R
    E.M.F of One cell : V

    3. The attempt at a solution

    I used the equation P = V^(2)/R

    Since the Voltage across "g" will be 2V and its Resistance is exactly the same as in the reference Attachment, "g" will be brighter than normal.
    Similarly, since the Voltage across "h" is going to be V, "h" must be of normal brightness.

    I am not sure if my answers make sense since if we apply the 2nd formula : P=R*I^2
    we would get a different set of results .

    Is it O.K to just rely on one of the two formulas and deduce the final answer based on say P=V^(2)/R ? Would the answers be authentic ?

    Attached Files:

  2. jcsd
  3. Jan 12, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Not if you do it correctly. Pls post your working.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook