Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why don't electronics care if it's DC or AC current?

  1. Jul 17, 2012 #1
    I understand AC is economic for transportation and easy to produce from converting mechanical energy into electrical energy.

    However, why don't electronics turn on and off because of this alternating nature of the current? For light bulb, maybe it does turn on and off and our eyes don't have fast enough *shutter speed* to capture the off moment so we are just seeing the average brightness of the light bulb.

    But what about computers? They did something to the battery so it doesn't turn off when current reaches its 0 point?
  2. jcsd
  3. Jul 17, 2012 #2
    An incandescent light turns on and off 120 times a second (the polarity reverses at double the operating frequency. The filiment doesn't have time to cool off so we don't "see" the flicker.
    In electronics (like your computer) the power supply converts the AC to DC so the electronics can do their job in an uninterupted flow.
  4. Jul 17, 2012 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    This is puzzling. What makes you think electronics "don't care"?

    I have a power adapter that converts the household AC into a 12V DC for one of my "electronics". This is an obvious example that it DOES matter if it is AC or DC for some components!

  5. Jul 17, 2012 #4
    Some electronics do care about AC or DC.

    Transformers only work on AC power.

    Capacitors block DC but will allow an AC current to pass (also the frequency of the AC is important as a higher frequency passes through more easily)
  6. Jul 17, 2012 #5
    Ahh I see, thank you.

    So are all computer power units have DC output? Can I modify the connection so I can use it as a power source to let's say charge a capacitor?
  7. Jul 17, 2012 #6
    I wouldn't recommend modifying the power supply in your pc as it could be very dangerous due to the voltages involved and the fact you are using it for a purpose that it obvoiusly was never intended.

    If you wish to experiment with some basic electronic components you would be better off getting a cheap lab power supply as these will provide a safe source of power and are fused in case of any faults that may occur.

    If you can't get a lab power supply then you could use a battery snap to connect a 9V PP3 battery and that should be adequate for most small electronics circuits.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook