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!

Finding efficiency between transformers.

  1. Mar 4, 2012 #1
    Ok, I have a primary and secondary coil. I set up a transformer between them. Each has 400 turns of coil(N). The primary coil produces a potential difference of 2.988 V. The secondary coil has a potential difference of 0.0551 V.

    For the efficiency, I used the equation (Np*Vs)/(Ns*Vp) * 100%

    Np-turns of primary coil(400)
    Vs- potential difference of secondary coil(0.0551)
    Ns- turns of secondary coil(400)
    Vp-potential difference of primary coil(2.988)

    When I plug them in, I get 1.84% efficiency.

    Am I messing the formula up, plugging in the wrong values. etc?
    1.84% seems awfully low.
  2. jcsd
  3. Mar 4, 2012 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    For equal number of turns on the primary and secondary, a 100% efficient transformer would have equal voltages on the primary and secondary. But the problem statement does give an awfully low value for the secondary voltage, namely 1.84% of the primary voltage.

    Perhaps if you can you post the question in its exact wording, I can see if there is something we are missing.
  4. Mar 4, 2012 #3
    This was a lab experiment, and these values were measured or given. the two coils were set up with an iron core and were faced toward eachother with 2 voltage probes acting as a voltmeter.

    Later on for a separate trial, we had the iron core placed right through the transformer with still two 400 coils, and then I calculated a reasonable 60.4% efficiency using the same formula as earlier.

    I'm guessing that its a possibility that the more O-shaped iron core involved, the more efficient the transformer was, and that having no O-shaped iron core made it extremely, yet unbelievably, inefficient.
  5. Mar 5, 2012 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Okay, it makes more sense now. Without the iron core in place, the coils are not coupled as strongly to one another.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Finding efficiency between transformers.
  1. Find efficiency (Replies: 8)

  2. Transformer efficiency (Replies: 2)