half wave rectifiers and ripple factor

Discussion in 'Homework Help' started by micachu, Mar 1, 2015.

  1. micachu

    Thread Starter New Member

    Oct 13, 2014
    15
    0
    We constructed the circuit below
    upload_2015-3-1_14-53-6.png
    and when measuring the output we got a ripple factor of abut 25%.
    upload_2015-3-1_14-54-30.png

    We then added a 10 ohm resistor next to the capacitor as shown,
    upload_2015-3-1_14-56-32.png
    and the results were a ripple factor of 29%.
    upload_2015-3-1_14-57-26.png

    I've been stuck and can't figure out why the ripple factor went up just by adding a small resistor in series with the capacitor.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    Why would you think the resistor would have no effect?
    The load is drawing current from the capacitor during the time it's not being charged from the diode.
    This current has to flow through the resistor in series with the capacitor which causes a voltage drop across the resistor.
    This voltage drop subtracts from the capacitor output voltage so the capacitor voltage is lower than without the resistor.
    If you view the resistor voltage you will see this.
     
  3. WBahn

    Moderator

    Mar 31, 2012
    17,743
    4,792
    Also, it slows the rate at which the capacitor can be recharged.
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Plot the capacitor current with and without the resistor.
     
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