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Why on a oscilloscope does a.c current have a sine wave, whereas a d.c

  1. Mar 28, 2012 #1
    Why on a oscilloscope does a.c current have a sine wave, whereas a d.c current is just a straight line. Ive tried to look it up, but the explanations on the internet are a bit to complex for me to understand as i am only in my first year of alevel. If anyone could explain this to me, as simply as possible, i would be very grateful. Cheers
  2. jcsd
  3. Mar 28, 2012 #2


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    Science Advisor
    Gold Member

    Re: Oscilloscope

    The x-axis on the scope is time, the y-axis is your voltage/current. Since DC is constant in time, it's a straight line. The trace of an AC signal that is monofrequency is a sine wave in time.
  4. Mar 28, 2012 #3
    Re: Oscilloscope

    Simply put: a.c. stands for alternating current, hence the current is constantly going back and forth, creating a wave. d.c. stands for direct current, meaning the current is traveling in a constant direction so there is just a line.
  5. Mar 28, 2012 #4


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    Staff: Mentor

    Re: Oscilloscope

    Welcome to the PF.

    In addition to the answers you've already gotten, you might want to check out the Oscilloscope Primer from Tektronix:


    The link to it is the first in the list on that page. You will need to make a free account at the Tek website first, unfortunately, but the Primer should be worth the extra time that takes. The Primer starts off with the basics that you are interested in, and then there is plenty more information for whenever you are ready to study it.
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