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Homework Help: Help with designing an investigation

  1. Dec 8, 2016 #1
    1. The problem statement, all variables and given/known data
    We have been asked to design an investigation into transformers. The equipment list given is: coils of wire, iron core, ammeter, voltmeter, loudspeaker, signal generator and an oscilloscope.

    2. Relevant equations

    3. The attempt at a solution
    I know that you could investigate how changing the number of turns on the primary affects the secondary emf. However, we were asked to try and use all the equipment. What is the point of using a signal generator? Looking online it seems to say to stick to around 50Hz and nothing I have found seems to suggest changing the frequency of the primary current? Could this be done? What could I use the oscilloscope for?

    Thanks for any help offered.
  2. jcsd
  3. Dec 8, 2016 #2


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    That's correct but only if there is a primary emf. Check your equipment list again. What could you use to generate the primary emf?
  4. Dec 8, 2016 #3
    Thanks. Ok, so the signal generator would provide the emf? Why use a signal generator and not a power pack then?

    What would you use the oscillioscope for if you already have a voltmeter to measure the secondary emf? Also have no idea about the loudspeaker?
  5. Dec 8, 2016 #4


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    You could use an AC power supply if you have one (It would be too dangerous to use the AC mains directly).

    I agree there could be some redundancy. Can your voltmeter measure AC or just DC? Has the oscilloscope got two inputs?

    50Hz is just about in the audible range.
  6. Dec 8, 2016 #5
    I suspect the idea of the signal generator and oscilloscope is for you to do a frequency sweep of your coil circuit (with sig. gen.) and show the frequency response on the oscilloscope. You can also use the speaker to provide an audio confirmation that the signal starts to attenuate around the particular frequency that you predicted. (I am assuming that the signal generator operates in the audio range.)
  7. Dec 8, 2016 #6
    Thanks. It says in my guidance to use the signal generator to observe the operation of the transformer at different frequencies. So in terms of independent, dependent and control variables could I do the following:

    Change the frequency of the primary current (independent variable)
    Measure the voltage or oscilloscope reading on the secondary (dependent)
    Keep the number of turns the same (control)

    Would this work? What would be a suitable frequency range to test? 10-50Hz in steps of 10?

    I found out from someone else that the oscilloscope is mainly for us to see that the waveform on the secondary is unchanged whatever that means?
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