Finding power consumed by an electric razor

  1. A tourist takes his 21 W, 120 V AC razor to Europe, finds a special adapter, and plugs it into 220 V AC. What power does the razor consume as it goes up in smoke?


    attempt at solution:
    I used P=IV for 120 V to find the current, and using that number, plugged the numbers into the equation for 220V. The hint for the problem says that the resistance doesn't change for the razor in Europe... but I don't know how that helps. I feel like I'm missing something very easy but I'm stuck.
  2. jcsd
  3. berkeman

    Staff: Mentor

    Welcome to the PF. The key here is that the resistance doesn't change. I don't think you want to write:

    [tex]P = \frac{\Delta {V^2}}{R}[/tex]

    Instead, write two equations, one for the US and one for smokey Europe...
    Last edited: Feb 8, 2009
  4. Oh man that was easy.. I'm a little embarrassed. Thanks for the help!
  5. Hey seems like you guys figured it out. Can you help me. I'm stuck on the same question and I don't know what to do.
Know someone interested in this topic? Share this thead via email, Google+, Twitter, or Facebook

Have something to add?