Purpose for Components in Half Wave rectifier?

Discussion in 'General Electronics Chat' started by lsecrease, Sep 18, 2008.

  1. lsecrease

    Thread Starter New Member

    Sep 4, 2008
    6
    0
    Ok, in class we built a Half Wave rectifier first only using the diode and the 100K resistance.
    What is the purpose of the 100Kohm resistance and how is the power dissipated by the load calculated?

    Afterwards we added a
    100uF capacitor. Now whats the purpose of that?

    Also
    , what happens if we reverse the polarity of the 100uF capacitor in the circuit?
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    The resistor limits the current via Ohm's law. The power dissipated will be inversely proportional to the limit resistor. The capacitor smooths out the half-wave rectified sinusoid.

    If you reverse the polarity, you risk damaging the capacitor. These are not meant to be operated in reverse.

    Steve
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Actually, I believe the resistor was used as a load resistor.
    Have a look at the attached. One signal generator is simulated to produce a 12.6VAC RMS 60Hz sine wave, shown on the simulated O-scope as trace (A) in cyan.

    D1/R1 are the first part of your experiment. Note that the voltage across R1 is slightly less than the positive half of the sinewave input in the yellow (B) trace. This is due to the Vf (forward voltage drop) of D1. Note that trace B never falls below 0v.

    D2/R2/C1 are the 2nd part of your experiment. Note that the voltage stays "up there" between peaks. The capacitor acts more or less like a storage tank.
     
  4. Metalfan1185

    Active Member

    Sep 12, 2008
    146
    0
    the capacitor could explode, we used to do that all the time in electronics class, (such nice kids lol)
     
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