# A question about electrical Theory

Discussion in 'General Electronics Discussion' started by Electric-T, Aug 9, 2017.

1. ### Electric-T

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Jun 4, 2017
Im just curious here. This isnt anything im working on. I was sitting back thinking and it occured to me...
I know Power=Voltage X Amperage and when either voltage or current is increased, so is the power. Now this may not be a real life scenario but if the power in a circuit is increase (not due to any particular reason) what would be affected first? Current or Voltage? Why?
I look forward to reading what you guys come up with

2. ### Gryd3

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Jun 25, 2014
Power is the sum of the two individual properties.
To increase power, you *must* increase voltage and|or current.

However, in a real-world scenario increasing voltage will increase current at the same time... or increasing current will increase voltage at the same time.
There are minor exceptions... for example, reactive electronics may have capacitance and inductance which could skew the increase of voltage or current.

3. ### Tha fios agaibh

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Aug 11, 2014
Not really how it works.
In order to increase the power in a circuit either voltage increases, or resistance decreases. (..causing current to increase)

Another thing to consider:
If I had a 12 volt power supply that's rated with 10watts of power and I changed it to a 500watt power supply, the circuit itself would use the same power if the rest of the circuit was the same.

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4. ### Electric-T

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Jun 4, 2017
Take a va
What sparked the thought is my co workers vape. It is adjusted in watts. So what i gather is when you increase power you are pulling more current. The voltage shouldnt vary much since the power source is a battery.

5. ### Tha fios agaibh

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Aug 11, 2014
Perhaps it has a variable resistor that increases power by lowering resistance?

If the heater elements resistance increases the wattage (power) used decreases.

6. ### Electric-T

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Jun 4, 2017
Yeah I thought it didnt sound right. You can see by my last reply why I had the thought in the first place. Like i said i realise this isnt a real life scenario. Lets say on paper... 100 watt light, 10v , that gives us 10 amps. Take the same system and put in a 150 watt light. Would amperage or voltage be more likely to change? As i write this im realising the answer is probably amperage would increase...

7. ### Electric-T

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Jun 4, 2017
No the ohms are an advertised value. Unlikely to change much.

8. ### davennModerator

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Sep 5, 2009
not knowing the actual circuit in a vape .... it depends on how they are controlling the power level

The battery voltage may be getting regulated and therefore they are able to change it and thereby changing the power level
OR they just be changing the resistive load across the battery and thereby changing the power setting

most likely one of those 2 choices

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10. ### Tha fios agaibh

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Aug 11, 2014
That's true but the lower resistance of the 150w lamp is why amperage increases.

11. ### Electric-T

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Jun 4, 2017
http://www.ebay.com/itm/5pcs-Repalc...hm-/322564457159?_trksid=p2385738.m2548.l4275
As you see the values are advertised. Im not fixing one, just after looking at one the thought occurred. "Can all parts of the formula (V=IR) be manipulated? Surely you can...not in real life situations of course. Though i was purely thinking of only the numbers in the formula, i am kind of interested in how it works in a vape.

12. ### Electric-T

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Jun 4, 2017
This is true... I was forgetting about resistance. V=I^2×r if im not mistaken?

13. ### Electric-T

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Jun 4, 2017
I suppose the module itself could be pulling more current from the batteries.

14. ### Tha fios agaibh

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Aug 11, 2014
The advertised coil resistance may be fixed but resistance could be added externally by a potentiometer to change the wattage. Notice how there's a range of power?

You could also add a resistor to your 150watt light circuit example and lower the power it uses to 100 watts (..or lower)

15. ### Electric-T

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Jun 4, 2017
Yes i see where youre going with this. I suppose a potentiometer of some kind could be involved. If there was one in the module itself this makes perfect sense. I understand about the lightbulb too. This is probably how they achieve different resistance in different coils.

16. ### davennModerator

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Sep 5, 2009
except that with the wattages involved and the battery voltage, which appear to typically 3.7V Li Ion, current is going to be too high for a pot, it would get burnt out

3.7V / 0.5 Ohms (the lowest resistance) = 7.4A

how that equals 80W, I dunno, unless, as I suggested they use a V-reg ( and a boost converter one)

3.7V / 1.5 Ohms ( the highest resistance) = 2.5A

I will stick with my voltage regulator varying the voltage

Last edited: Aug 9, 2017
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17. ### Tha fios agaibh

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Aug 11, 2014
Probably right, although I've never seen one of these gizmos up close. I try and avoid smokers at all costs.
I suppose they could also use something like a rotary switch to select desired wattage?

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18. ### davennModerator

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Sep 5, 2009
yeah likewise

19. ### Electric-T

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Jun 4, 2017
The one i saw had a digital screen. Buttons were used to adjust voltage. I suppose i could google a schematic. But i enjoy the discussion. I find it more informational sometimes to discuss things on here rather than read data sheets and schematics and just thinking by myself

20. ### Tha fios agaibh

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Aug 11, 2014
It'd be interesting to see a schematic.

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