While solving a problem of a single wave half wave rectifier. using an "Ideal Diode"

Given Details:

Load Resistance - 1020 Ohms

Supply - 230V 50Hz AC (Connected in series)

To find : DC Load Current

Attempted Solution :

The current in the circuit (I0) = V*sqrt(2)/R = 0.3189 Amps

Since diode is reversed biased during the negative cycle. I0 is zero.

My assumption RMS value is the DC equivalent for sinusoidal waveform.

There fore the RMS Value of I0 = sqrt[(1/(2pi))integral(limits 0 to pi)(I0sin(100pi*t)*d(wt)]
/////because current doesnt flow in negative cycle of AC voltage

which evaluated to I0(rms) = Vmsqrt(2)/(2R) = 0.159 Amps

But the textbook i am following has given the answer to this question as 0.10159 Amps .

which is the Average current => I(avg) = [1/(2pi)]integral(limits 0 to pi)I0sin(100pi*t)*d(wt)]

Is DC load current equal to RMS value or average current?

  • \$\begingroup\$ "Is DC load current equal to RMS value or average Current?" To average current, if the textbook gave you value of 0.10159A as the answer, it's probably the average current because we are calculating the current of a half wave rectifier. \$\endgroup\$ Commented Dec 14, 2023 at 8:17
  • \$\begingroup\$ Connected in series What is the difference to in parallel here? \$\endgroup\$
    – greybeard
    Commented Dec 14, 2023 at 8:22
  • \$\begingroup\$ DC load current is the average current. RMS value is ... RMS. \$\endgroup\$
    – Antonio51
    Commented Dec 14, 2023 at 8:31
  • \$\begingroup\$ @ElectronSurf , but shouldn't the "DC" load current be the RMS , as RMS of a sinusoid is the steady state DC current which produces the same heat, effectively ( DC Current )? \$\endgroup\$ Commented Dec 14, 2023 at 10:06

2 Answers 2


My assumption RMS value is the DC equivalent for sinusoidal waveform.

Your assumption is incorrect. Here's a reminder of the various options and please take note that you need to use the mean rectified value: -

enter image description here

Image from here.

The peak current you have calculated correctly i.e. 0.3189 amps but, if you want the DC average current when rectified you then divide by \$\pi\$ to get 0.1015 amps.

  • \$\begingroup\$ Thank you Andy, to summarize , DC Load Current is the mean rectified magnitude ( Average current in the circuit ? . \$\endgroup\$ Commented Dec 14, 2023 at 10:03
  • \$\begingroup\$ @AnirudhSrikanth correct. If we are done here, please take note of this: What should I do when someone answers my question. If you are still confused about something then leave a comment to request further clarification. \$\endgroup\$
    – Andy aka
    Commented Dec 14, 2023 at 10:10
  • \$\begingroup\$ Hi, Andy why are you suspended? 😨 \$\endgroup\$ Commented Dec 14, 2023 at 18:31
  • \$\begingroup\$ @ElectronSurf I can't comment on this. \$\endgroup\$
    – Andy aka
    Commented Dec 17, 2023 at 17:03
  • \$\begingroup\$ There's something wrong with this sub! \$\endgroup\$ Commented Dec 18, 2023 at 7:11

The DC equivalent of a non-constant current depends on the effect under scrutiny:

When used to charge an accumulator, average. (Imagine pure AC.)
(Guess why charger suppliers loved the sound of effective in effective current when it wasn't.)

With (resistive) heating, RMS.


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