half wave rectifier

Ed wrote:
> Don wrote:

<snip>

>> "If we keep 250VAC constant then V^2 (eg 250VAC^2) is a constant" (as
>> stated above) is my premise. This 250VAC is treated as Vmains by me.
>>      My mind mechanically treats Vmains as a constant - because it is.
>> Most electric outlets in my world source about 120 VAC regardless of the
>> load connected.
>>      When Vmains is held constant, a doubling of Rmains halves Pmains.
>
> Correct. He'll get half power out of the combination of HR (the heater
> resistance) plus AR (the added resistance). The original power was 3000
> watts. Half power is 1500 watts. So he'll get 750 watts out of AR and
> 750 watts out of HR.
>
> BUT THE OP WANTS 1500 WATTS OUT OF HR.
>
> Your math solves the wrong problem.
> From the op: "As part of an experiment with solar, I want to drive my
> 220V 3kW immersion heater with a suitable diode so that the effective
> power is ~1.5kW..."

There's actually a couple of problems. One problem is people who try to
shout down wrong thought of how doubling a resistor halves the power. My 
math solves this problem by illustrating an exception.
    If you keep reading my previous followup (the part you snipped)
you'll discover how my math eventually illustrates a solution to the 
OP's 1500 W problem. But, you need to read my followup in its entirety
to see it.

In the end, sloppy nomenclature caused this thread's miscommunication.

    "When I use [the word volt]," Humpty Dumpty said in rather a
    scornful tone, "it means just what I choose it to mean -
    neither more nor less."

Danke,

-- 
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

On 04/07/2023 01:05, Ricky wrote:
> On Monday, July 3, 2023 at 5:40:51 PM UTC-4, TTman wrote:
>>> No.
>>> ...HR= 20 Ohms. Add another resistor in series = 20 Ohms
>>>> making Rt - 40 Ohms.
>>>>    If I apply 250 V across 40 Ohms, I get 125V across each resistor.
>>>>
>>>
>>> Correct.  Now for goodness sake do the next step in the math.
>>>
>>> 125 volts across 20 ohms produces 781.25 watts in the pot
>>> heater and 781.25 watts in the added resistor.
>>> But you said you want 1500 watts in the pot heater.
>>>
>>> Ed
>> That's a surprise...
> 
> That's the point.  You don't understand this and seem to be unwilling to learn anything new.  You say you don't understand what others post, then repeat the wrongthink that you have in your head.  Maybe now you will pay a bit more attention to what others have posted and learn something about the problem.
> 
Yes, I see it, but it defies apparent simplistic logic.I see it's V xV 
or IxI for power, hence the quarter/sq root. No wonder nothing I 
designed/built worked...

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On Tuesday, July 4, 2023 at 7:02:34 AM UTC-4, TTman wrote:
> On 04/07/2023 01:05, Ricky wrote: 
> > On Monday, July 3, 2023 at 5:40:51 PM UTC-4, TTman wrote: 
> >>> No. 
> >>> ...HR= 20 Ohms. Add another resistor in series = 20 Ohms 
> >>>> making Rt - 40 Ohms. 
> >>>> If I apply 250 V across 40 Ohms, I get 125V across each resistor. 
> >>>> 
> >>> 
> >>> Correct. Now for goodness sake do the next step in the math. 
> >>> 
> >>> 125 volts across 20 ohms produces 781.25 watts in the pot 
> >>> heater and 781.25 watts in the added resistor. 
> >>> But you said you want 1500 watts in the pot heater. 
> >>> 
> >>> Ed 
> >> That's a surprise... 
> > 
> > That's the point. You don't understand this and seem to be unwilling to learn anything new. You say you don't understand what others post, then repeat the wrongthink that you have in your head. Maybe now you will pay a bit more attention to what others have posted and learn something about the problem. 
> >
> Yes, I see it, but it defies apparent simplistic logic.

Yes, that's what we've tried to tell you.  You can't just say, double resistance, so half power in the pot.  


> I see it's V xV 
> or IxI for power, hence the quarter/sq root. No wonder nothing I 
> designed/built worked...

Yeah, if you ignore the math, things don't go well. 

What made the lightbulb come on? 

-- 

  Rick C.

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>>>> That's a surprise...
>>>
>>> That's the point. You don't understand this and seem to be unwilling to learn anything new. You say you don't understand what others post, then repeat the wrongthink that you have in your head. Maybe now you will pay a bit more attention to what others have posted and learn something about the problem.
>>>
>> Yes, I see it, but it defies apparent simplistic logic.
> 
> Yes, that's what we've tried to tell you.  You can't just say, double resistance, so half power in the pot.
> 
> 
>> I see it's V xV
>> or IxI for power, hence the quarter/sq root. No wonder nothing I
>> designed/built worked...
> 
> Yeah, if you ignore the math, things don't go well.
> 
> What made the lightbulb come on?
> 
I went back to basics. I admit I just didn't think about this properly 
at all. I'm 72 and clearly my brain is screwed and incapable of clear 
thinking. Never mind, I won't be long for this world and I won't have to 
think about things like this.

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On Tuesday, July 4, 2023 at 12:36:10 PM UTC-4, TTman wrote:
> >>>> That's a surprise... 
> >>> 
> >>> That's the point. You don't understand this and seem to be unwilling to learn anything new. You say you don't understand what others post, then repeat the wrongthink that you have in your head. Maybe now you will pay a bit more attention to what others have posted and learn something about the problem. 
> >>> 
> >> Yes, I see it, but it defies apparent simplistic logic. 
> > 
> > Yes, that's what we've tried to tell you. You can't just say, double resistance, so half power in the pot. 
> > 
> > 
> >> I see it's V xV 
> >> or IxI for power, hence the quarter/sq root. No wonder nothing I 
> >> designed/built worked... 
> > 
> > Yeah, if you ignore the math, things don't go well. 
> > 
> > What made the lightbulb come on? 
> >
> I went back to basics. I admit I just didn't think about this properly 
> at all. I'm 72 and clearly my brain is screwed and incapable of clear 
> thinking. Never mind, I won't be long for this world and I won't have to 
> think about things like this.

So, that is what I have to look forward to in three years?  Crap! 

I nearly stopped working for some four or five years, and I the next time I had a serious task, I could tell I had lost something.  But then I got a sizeable job and had to work intensely for months.  It pretty much all came back.  I'm not as quick with numbers, not being able to do as much in my head now.  But the logic is all there.  

One of the things I do to get to sleep is to recite the alphabet backwards.  So, I'm ready for the intoxication tests now.  

-- 

  Rick C.

  +-++ Get 1,000 miles of free Supercharging
  +-++ Tesla referral code - https://ts.la/richard11209

>>>
>> I went back to basics. I admit I just didn't think about this properly
>> at all. I'm 72 and clearly my brain is screwed and incapable of clear
>> thinking. Never mind, I won't be long for this world and I won't have to
>> think about things like this.
> 
> So, that is what I have to look forward to in three years?  Crap!
> 
> I nearly stopped working for some four or five years, and I the next time I had a serious task, I could tell I had lost something.  But then I got a sizeable job and had to work intensely for months.  It pretty much all came back.  I'm not as quick with numbers, not being able to do as much in my head now.  But the logic is all there.
> 
> One of the things I do to get to sleep is to recite the alphabet backwards.  So, I'm ready for the intoxication tests now.
> 
I count / visualise binary up to 127...It's interesting at 40,80 and 
120... utter nerd :)

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