Watts an Ohm?

[Vaper Bob]

This is going to be a very very dumb question. But bear in mind I failed every physics exam in school and occasionally lapse into numerical dyslexia. I'm also new to vaping. Ok, so here it is.

Consider two setups:
Setup A is a VV/VW mod, say a Provari P3 (as I have), with a good tank with a 1.5 ohm coil installed.
Setup B is exactly the same, but with a 2 ohm coil installed.
Both setups are set to 10 Watts.
You push the button........

Which coil gets hotter? Which setup results in more voltage? Which setup has more current running through the coils? Or are all three (heat,voltage, current) the same thing?

See, I told you it would be a dumb question.

 

[edyle]

This is going to be a very very dumb question. But bear in mind I failed every physics exam in school and occasionally lapse into numerical dyslexia. I'm also new to vaping. Ok, so here it is.

Consider two setups:
Setup A is a VV/VW mod, say a Provari P3 (as I have), with a good tank with a 1.5 ohm coil installed.
Setup B is exactly the same, but with a 2 ohm coil installed.
Both setups are set to 10 Watts.
You push the button........

Which coil gets hotter? Which setup results in more voltage? Which setup has more current running through the coils? Or are all three (heat,voltage, current) the same thing?

See, I told you it would be a dumb question.

1: Which coil gets hotter?
Depends on the detail of the coil. Ohms alone can't say.

2: Which setup results in more voltage?
The higher ohm coil will need higher voltage for the same watts.

watts = volts x volts/ohms
10 = volts x volts /ohms
if ohms = 1.5 then volts = 3.9 volts
if ohms = 2.0 then volts = 4.5 volts

3: Which setup has more current running through the coils?
watts = amps x amps x ohms
For the same watts, higher ohms means lower amps.
The 1.5 ohm has more current than the 2 ohm coil.

 

[HighPlainsPuffer]

watts = (Voltage * Voltage)/resistance

so with Setup A you would be looking at 3.87 volts

Setup B at the same 10 watts is at 4.47 volts

Since both setups use the same wire type, setup B will have more mass, so it will heat up at a slower rate as compared to setup A during the same set time. Heat (joules) is pretty much the same as watts (I think).

 

[Vaper Bob]

1: Which coil gets hotter?
Depends on the detail of the coil. Ohms alone can't say.

2: Which setup results in more voltage?
The higher ohm coil will need higher voltage for the same watts.

watts = volts x volts/ohms
10 = volts x volts /ohms
if ohms = 1.5 then volts = 3.9 volts
if ohms = 2.0 then volts = 4.5 volts

3: Which setup has more current running through the coils?
watts = amps x amps x ohms
For the same watts, higher ohms means lower amps.
The 1.5 ohm has more current than the 2 ohm coil.

Good God, no wonder I failed those exams. I'm going to read this over and over till I get it. You said "For the same watts, higher ohms means lower amps". I think amps=current, and in this context, equals amount of heat. Is that right? If so, then for the same watts, the higher the ohms, the less the heat. Correct or not?

 

[Vaper Bob]

watts = (Voltage * Voltage)/resistance

so with Setup A you would be looking at 3.87 volts

Setup B at the same 10 watts is at 4.47 volts

Since both setups use the same wire type, setup B will have more mass, so it will heat up at a slower rate as compared to setup A during the same set time. Heat (joules) is pretty much the same as watts (I think).

But which setup would generate more heat in the coil?

 

[suprtrkr]

+1 to everybody above. To answer @HighPlainsPuffer , watts are a measure of power while joules are a measure of work, a/k/a/power x time. A joule is a measure meaning 1 watt for one second. 2 joules = 2 w for 1 second = 1w for 2 seconds, and so forth.

 

[suprtrkr]

But which setup would generate more heat in the coil?

Now you're getting into thermodynamics. If we assume both coils use the same wire-- no reason to make that assumption-- they should both attain the same temperature, but the higher value coil will take longer to get there.

 

[HighPlainsPuffer]

Setup A will produce more heat quicker. Setup B can reach the same overall temperature but will take longer to do so. Setup B, however, could be run at less than 10 watts, the same voltage as setup A at 3.9 and although the heat would not be there the vapor would be, and would be more efficient for your battery longevity.

Thanks @suprtrkr I appreciate that explanation, brings back memories of high school, when I learned things and immediately forgot them! Old physics teacher would cringe...

 

[Vaper Bob]

Now you're getting into thermodynamics. If we assume both coils use the same wire-- no reason to make that assumption-- they should both attain the same temperature, but the higher value coil will take longer to get there.

So if you sub-ohm, you're using less volts to get more current through the coil?

 

[suprtrkr]

So if you sub-ohm, you're using less volts to get more current through the coil?

Not quite. You use less volts to get the same current through the coil. Volts, amps and ohms are in a solid relationship called Ohm's Law. Any time you change any value one or both of the others must change to balance the equation. Here's a graphic where p = watts, e = volts, i = amps and r = ohms.

 

[HighPlainsPuffer]

So if you sub-ohm, you're using less volts to get more current through the coil?

Due to the lower resistance in the coils, sub ohm typically uses more wattage to achieve the same voltage.

 

[Vaper Bob]

Setup A will produce more heat quicker. Setup B can reach the same overall temperature but will take longer to do so. Setup B, however, could be run at less than 10 watts, the same voltage as setup A at 3.9 and although the heat would not be there the vapor would be, and would be more efficient for your battery longevity.

Thanks @suprtrkr I appreciate that explanation, brings back memories of high school, when I learned things and immediately forgot them! Old physics teacher would cringe...

I thought more heat means more vapour. Or are you saying if you reduced the voltage in setup B, you need to hold the button for longer to get the same vapour?

 

[suprtrkr]

I thought more heat means more vapour. Or are you saying if you reduced the voltage in setup B, you need to hold the button for longer to get the same vapour?

More heat means more vapor (within the ability of the wick to bring juice to the coil, and the coil surface area.) But you are confusing yourself by holding watts constant in your example. If you want more heat, throw more watts at it.

 

[HighPlainsPuffer]

I thought more heat means more vapour. Or are you saying if you reduced the voltage in setup B, you need to hold the button for longer to get the same vapour?

Heat in your vapor is what I was referring to, sorry. A warm vape vs a cold vape.

 

[suprtrkr]

I thought more heat means more vapour. Or are you saying if you reduced the voltage in setup B, you need to hold the button for longer to get the same vapour?

Or another answer to the same question: The lower value coil will make vapor faster than the higher value coil, given the same watts.

 

[Vaper Bob]

Not quite. You use less volts to get the same current through the coil. Volts, amps and ohms are in a solid relationship called Ohm's Law. Any time you change any value one or both must change to balance the equation. Here's a graphic where p = watts, e = volts, i = amps and r = ohms.

Let me see, the less the ohms, the less the resistance to current at a given voltage. Am I getting there?

 

[suprtrkr]

Let me see, the less the ohms, the less the resistance to current at a given voltage. Am I getting there?

Yes. Ohms are a measure of resistance to current. The smaller the number, the less resistance.

 

[HighPlainsPuffer]

Ok so with vaping a 1.0 ohm coil, once you've raised the wattage to a certain amount you are at the limits of the voltage capabilities of your mod. Sub ohm allows for lower than 1.0 ohm to use less volts, just like you're thinking, but it allows for much more wattage to be used before that voltage range is reached. More wattage typically means more vapor. More voltage can lead to a warmer vapor. As a result, high wattage on sub ohm setups can allow for warm clouds of vapor.

 

[suprtrkr]

Ok so with vaping a 1.0 ohm coil, once you've raised the wattage to a certain amount you are at the limits of the voltage capabilities of your mod. Sub ohm allows for lower than 1.0 ohm to use less volts, just like you're thinking, but it allows for much more wattage to be used before that voltage range is reached. More wattage typically means more vapor. More voltage can lead to a warmer vapor. As a result, high wattage on sub ohm setups can allow for warm clouds of vapor.

Excellent! Another way to put it and very clear.

 

[suprtrkr]

You might have a glance at @Baditude 's blog, my friend:
(14) Ohm's Law for Dummies (Vapers) | E-Cigarette Forum
(16) Explain it for the dumb noob: Ohm's Law calculations. | E-Cigarette Forum