1. Not finding help here? Sign up for a free 30min 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!

How Many Amps flow through the lightbulb

  1. Oct 31, 2009 #1
    http://img257.imageshack.us/img257/7161/physics.png [Broken]

    I only have one more chance at this problem and I can't understand why it isn't 1. I assumed that power in = power out and power = current x voltage. If the voltage remains constant, wouldn't the current as well?

    "In the circuit shown, how many volts are impressed across and how many amps flow through the lightbulb?"

    (120V ac)--> 100 turns -->10 turns [1 A] --> 10 turns --> 100 turns --> lightbulb
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Oct 31, 2009 #2

    rl.bhat

    User Avatar
    Homework Helper

    Input power = [120V]*[I A]
    Out put power = [..V]*[..A] ?
     
  4. Nov 1, 2009 #3
    i'm still confused... are you saying 120v * 1 amp? Sorry, I am really bad at electricity, but dont the turns mean anything?
     
  5. Nov 1, 2009 #4

    rl.bhat

    User Avatar
    Homework Helper

    120v * 1 amp
    It is not one, it is 'I'
    In the first transformer, what is the out put power? From that find the input current.
     
  6. Nov 1, 2009 #5
    so if I use V=IR how would I calculate I? I= V/R. but what do I plug in as the resistance? I am so bad at physics :(
     
  7. Nov 1, 2009 #6

    rl.bhat

    User Avatar
    Homework Helper

    From the tern ratio you can find the output voltage in the first transformer. The current is given. Find the output power. Equate it to input power and find the input current.
     
  8. Nov 1, 2009 #7
    I am still confused. "The current is given?" maybe I am just fundamentally misinterpreting the diagram. Does it say "1A" or "IA." and either way, what does it mean?
     
  9. Nov 1, 2009 #8
    I figured it out! Thank you so much!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook