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Homework Help: Basic Electronics True or False Questions

  1. Nov 17, 2011 #1

    Femme_physics

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    Gold Member

    I also needed to explain my answer... I hope it's all true. Can you tell me?


    True or False
    -------------
    The Effective Voltage in our houses (Israel) is 220 Volts, therefor the Max VOltage is 380 Volts.

    FALSE

    220[itex]\sqrt[]{}2[/itex] = 311

    ---

    The equivalent inductance between points AB in the following circuit is 90 mh.

    http://img824.imageshack.us/img824/3699/coils.jpg [Broken]


    FALSE, due to the calculations I made in the pic.

    ---

    The Duty Cycle of the final repeating signal is 66.66%.

    http://img545.imageshack.us/img545/570/31464876.jpg [Broken]

    True.

    4/6 = 66.66%

    ---

    In a rectification circuit of an AC sinusoidal voltage with the help of a single diode we get the following wave form after rectification.

    http://img197.imageshack.us/img197/8518/booep.jpg [Broken]

    FALSE. You need 4 diodes for rectification such as in a Diode Bridge.

    ---

    The conductance of resistor R in the following circuit is 10 Mho.
    http://img705.imageshack.us/img705/4672/dadamn.jpg [Broken]

    FALSE

    G = 1/100 = 0.01 Mho

    ----

    The Frequency of the following repeating signal is 6 Kilohertz.

    http://img825.imageshack.us/img825/4918/xttx.jpg [Broken]

    FALSE

    f = 1/6
    omega = 2pif = 2 x pi x 1/6 = 1.047 Hertz
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Nov 17, 2011 #2

    gneill

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    Staff: Mentor

    Actually, you can use a single diode for rectification. You get what's called half-wave rectification (effectively chopping off the lower or upper half of the waveform, depending upon the diode's direction).

    https://www.physicsforums.com/attachment.php?attachmentid=41007&stc=1&d=1321554469

    The real problem here is fact that the shown resulting waveform does not resemble a sinewave nor any part of one.
     

    Attached Files:

    Last edited by a moderator: May 5, 2017
  4. Nov 17, 2011 #3
    It's perfectly possible to rectify an AC voltage with only a single diode, it just isn't very efficient. What do you think is the waveform that is produced, if you put an ac voltage source in series with a diode?

    The frequency of a signal is 1/period. [itex]2 \pi [/itex] doesn't come in to it. I think you're confused with the angular frequency.
     
  5. Nov 17, 2011 #4

    Femme_physics

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    Gold Member

    Last edited by a moderator: May 5, 2017
  6. Nov 17, 2011 #5
    I agree with the other responses. You get this rectified voltage with 1 diode.
    The frequency =1/T = 1/6x10^-3 =167Hz (the time scale is in milliseconds)
    Cheers
     
  7. Nov 17, 2011 #6

    Femme_physics

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    Again, made a mistake :smile: The question is if I can rectify to THIS

    http://img197.imageshack.us/img197/8518/booep.jpg [Broken]

    With just one diode.
     
    Last edited by a moderator: May 5, 2017
  8. Nov 17, 2011 #7
    that is what you get with 4 diodes!!
     
  9. Nov 17, 2011 #8

    Femme_physics

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    Yes, that's what I meant. I just posted the wrong pic. :smile: There you go! Thanks.

    So was I right about everything?
     
  10. Nov 17, 2011 #9
    The frequency question is wrong because the time scale is in ms (millisecs) and the time for 1 cycle (T) is 6 x 10^-3s.
    The frequency =1/6x10^-3
     
  11. Nov 17, 2011 #10

    Femme_physics

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    1/6x10^-3 = 166.6667 hertz

    So the answer is 0.16 kilohertz and not 6 kilohertz. Therefor the answer is still "FALSE", correct?
     
  12. Nov 17, 2011 #11
    that is it !!
     
  13. Nov 17, 2011 #12

    Femme_physics

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    Gold Member

    You rock, technician! Thanks a bunch.
     
  14. Nov 17, 2011 #13
    Thanks a lot.... can't wait to see what you come up with next!
     
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