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!

What resistance is needed if current is .300 A?

  1. May 15, 2008 #1
    1. The problem statement, all variables and given/known data
    A 75.0 W bulb is connected to a 120 V source. A lamp dimmer puts a resistance in series with the bulb. What resistance would be needed to reduce the current to .300 A?


    2. Relevant equations
    R=V/I


    3. The attempt at a solution

    R=120/.3A=400 ohms. The answer is 210 ohms. What am I missing?
     
  2. jcsd
  3. May 15, 2008 #2
    Here's another relevant equation.

    [tex](R_{bulb} + R_{dimmer} = V_{total}/I[/tex]
     
  4. May 15, 2008 #3
    Here is one more:

    [tex] P=V^2/R [/tex]
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: What resistance is needed if current is .300 A?
  1. Current and Resistance (Replies: 1)

Loading...