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: Voltage of bulb in the circuit

  1. May 26, 2015 #1
    1. The problem statement, all variables and given/known data
    What is the voltage of the bulb D? Given the total voltage supplied by the cells is 4 watts and each bulb is identical and has a resistance of 3 ohms

    2. Relevant equations

    3. The attempt at a solution
    By assuming bulb A,B, and C as a group , their effective resistance would be 2 ohms.
    Thus, the effective resistance of the circuit is Effective resistance of bulb A,B,C + resistance of Bulb D = 5 ohms
    Hence, the current across the circuit is total voltage supplied / effective resistance of the whole circuit = 4/5 A. Therefore, the voltage of bulb D is 4/5A x 3 ohms = 12/5 W

    *forgive me for my random attempt , since my teacher never taught me anything about this part

    Attached Files:

  2. jcsd
  3. May 26, 2015 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    The units given in the statement of your problem don't make sense.

    What is the problem, word for word, as it was given to you?
  4. May 26, 2015 #3
    There is an error here. I think you mean the voltage supplied by the cells is 4 volts

    voltage is a measure of the EMF (electromotive force)
    w is for watts and it is a measure of energy over time (power) 1 watt = 1 joule for 1 second
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted