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Homework Help: Number of windings for 120-V household circuit?

  1. Mar 19, 2007 #1
    A model train requires 6 V to operate. If the primary coil of its transformer has 240 windings, how many windings should the secondary have if the primary is connected to a 120-V household circuit?


    V1/V2 = N1/N2



    my teacher went over this with the class, and said that N2= 6V/120V(240), so it equals 12. I don't get how he got that answer. Can someone help me to understand please?
     
  2. jcsd
  3. Mar 19, 2007 #2

    marcusl

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    He is correct. This type of transformer is sometimes called a stepdown transformer because it transforms a big voltage to a smaller one. The turns ratio equals the desired voltage ratio, so
    n2/240 = 6/120
    and n2=12 as claimed.
     
  4. Mar 19, 2007 #3
    I see. Thank you. For some reason, how you wrote it, it clicked in my head.
     
  5. Mar 19, 2007 #4

    marcusl

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    You're welcome!
     
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