Usa Wpg Not Uk?

[piper]

But surely I=V/R

Therefore:

If you use a device rated for the UK in America it will draw only half the power...

230W in the uk = 1A, or 1 Ohm

Put that 1 Ohm against the US voltage of 110V and you will get 110W.

N'est pas?

Ohms are a rating of electrical devices resistance so I don’t think that really fits in here. A device will draw as much current (amps) as it needs to run. So it will draw twice as many amps in the US then in the UK to run. As an example let’s use a 3kW toaster.

UK 3,000 = I * 230 there for runs on 13 Amps
US 3,000 = I * 110 there for runs on 27 Amps

Although if you did use an UK toaster in American it might well blow, as they would be rated for around 15 amps max.

 

[andywg]

But for it to draw more current it would have to have a lower resistance. The heating element in a toaster is a wire with a certain resistance value. the wire will not realise it has crossed the Atlantic and change its properties.

 

[piper]

Nope, the resistance of the wire will vary with the amount of current running through it. Its resistance will decrease as the element heats up. Thus allowing more current to flow.

The toaster would know it’s crossed the Atlantic, as it would be trying to draw more current from the lower voltage supply, which would in turn blow its fuse.

! Welcome to America toaster you no longer work !

 

[andywg]

*continues off topic*

If that's the case, then why does the Mrs Hairdryer work at half pace when we are in Florida? By your theory it would still work the same. I would have purely put it down to the resistance. (or more precisely the reactance) of the motor and the heater.

The hairdryer is made to pull (say) 1 Amp from the UK and as such has an apparant resistance of 230 Ohms to allow for 230W application.

That resistance is a property of the material. It will not change purely by having less voltage on it.

Current drawn (I) = V/R. If you want more current what do you do? You either increase the voltage or ddecrease the resistance. The resistance will not decrease on its own to match a lower voltage. It would need to be physically changed.

Think in terms of a simple circuit of a power supply and a resisitor with the appropriate measuring apparatus. By lowering the voltage alone you will not see an increase in the current and thus a stabilisation in Power.

Edited to comply with latest IEE regs...

 

[piper]

How did we get into this!!!!!!!!!! There are so many factors to consider and I doubt a further debate is going to help any one.

 

[Ptarmigan]

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[akudewan]

*cough* I had asked a question people, and I really need this sorted out before I fetch my drill machine

Since we are already a bit off topic, I have another question. I bought a 36 watt cool-daylight fluorescent bulb yesterday for my tank, the thing is, that bulb can light my my whole room...Do you guys have SO MUCH LIGHT for the tank ?? confused.gif

PS: I already have a 20watt tube in my tank, and the 36 watt will increase the lighting to 2.43 wpg

Is it normal for people to ignore you when you are approaching 200 posts? Or maybe I'm just a blabbermouth...

 

[piper]

Sorry mate I couldn't answer that as I dont even have a cycled tank yet

 

[andywg]

*cough* I had asked a question people, and I really need this sorted out before I fetch my drill machine

Since we are already a bit off topic, I have another question. I bought a 36 watt cool-daylight fluorescent bulb yesterday for my tank, the thing is, that bulb can light my my whole room...Do you guys have SO MUCH LIGHT for the tank ?? confused.gif

PS: I already have a 20watt tube in my tank, and the 36 watt will increase the lighting to 2.43 wpg

Is it normal for people to ignore you when you are approaching 200 posts? Or maybe I'm just a blabbermouth...

All depends on the size of the tank and the purpose. My 6x2x2 has 300W of Metal Halides over it, and should (if I ever get my lazy backside into gear) be supplemented by around 104W of VHO T5 lighting. If you check Nav's reef, that thing has in excess of 900W of lighting. Horses for Courses.

If you want a heavily planted tank then that's a good amount of light, though you will need to supplement with CO2 and fertiliser to prevent massive algae outbreaks. When using loads of light, you may also need to watch the heat rising.

Ptarmigan

I cede to your better knowledge. IT's around 4 years since I did Electrical and electronic principles (no more Kirchhoff's Theroem for this little desk rider )

 

[Ptarmigan]

.

 

[piper]

Almost started to get technical again then but decided to stop my self typing...........

Need to do lighting calculations to prove a point , ...... NO NO , must hold back

 

[andywg]

The lumens and lux per watt are more important. MH is not as necessary in FW, but for corals you need a good punch into the water. Unless you overdrive T5 VHO (but that is nowhere near necessary for FW plants...)

Also of great importance is the colour temperature of the bulb. The closer to the sun the better, though I seem to recall that bluer = more height but sparser leaves, where redder = less height, more lush growth.

Restrain yourself Piper though this could make a good topic in Hardware...


And Thevnin and Norton were my favorites. Used to love those things (though I never once used them in a practical situation...).

Hell, Norton just seemed a copy of Thevenin to me (that was the order I was taught).

 

[Ptarmigan]

.

 

[andywg]

Remember you need a lot more than the colour temp and intensity, when I upgraded my 85 (UK) gallon from T5 to MH, I created the world's largest hair algae farm...

But on the deeper 150 gallon (with the lights further from the surface) it's fine.