surfarthur
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Posts posted by surfarthur
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JA, I am an electrician, I do know what I am talking about. You are correct in saying that when you are dealing with AC, you need to include power factor, however for the purposes above, talking about a purely resistive device (a heating element), then the power factor will be 1, therefore you can use the DC calculations. The human body may not be purely resistive, in fact a quick google search suggests that there will be a small amount of capacitance, which will affect the total current flowing through your body. This is where the different frequencies have an effect, however assuming the same frequency of 50 Hz and a small amount of capacitance, this would not significantly change the amount of current flowing.
In fact, the only difference between ohms law for DC and ohms law for AC is that instead of resistance, we use impedance, which is a combination of inductive reactance, resistance and capacitive reactance. If you are talking about a purely resistive device, then resistance = impedance.
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If you did that JA, then the transformer would be powered even when the lights are switched off - 1 per room is a better option, that way the transformer could be after the light switch - so if you only have a few lights in each room (e.g. a bedroom light, then the mains powered LED lights will be a better option.
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Fact is that LEDs use a transformer. Each tranny can cope with a lot more lights than a transformer for Halogen lights.
The really important thing is that LEDs tend to last around 30 times longer than halogens.
We have replaced all out halogens with LED downlights, no actual numbers but gut feeling is that they have saved around 5% on power bills.
You can get mains LED lights that do not require a transformer an are a direct replacement for standard light globes.
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How many amps will be needed on a 110 circuit for a 1 Kilowatt heater.
How many for the same on a 220 circuit.
What heats the elements. Is it voltage or current?
at 110V, using P = V x I, or I = P / V, a 1kW element will draw 1000 / 110 = 9.09A. As an element can be considered purely resistive, we can do away with power factor for now.
Using Ohms law, I = V / R, we can now work out the resistance of the element. R = V / I, therefore R = 110 / 9.09 = 12.1 Ohms.
at 220V, using P = V x I, or I = P / V, a 1kW element will draw 1000 / 220 = 4.55A.
Using Ohms law, I = V / R, we can now work out the resistance of the element. R = V / I, therefore R = 220 / 4.55 = 48.35 Ohms.
If we used the 1kW element that is designed for 110V, with a resistance of 12.1 Ohms, on a 220V system, we would be drawing 18.3A instead of 9.09A, and we would probably have a fire before too long.
Following so far?
Assuming that the shock at 220V and the shock at 110V follow the same path, then we can assume that the resistance of the human body remains the same.
A quick google search suggests that a figure of somewhere between 300 and 1000 Ohms would be about right for a human body. Lets use 500 Ohms.
Back to Ohms law, R = V / I, so I = V / R. therefore at 110V, I = 110 / 500 = 0.22A. At 220V, I = 220 / 500 = 0.44A. Therefore, the higher the voltage, the higher the current that will flow through your body assuming that the entry and exit points are the same in both cases.
This is basic high school science.
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This must be on every page of this thread.....Page 3 secured.
and now page 4.
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Didn't know until I just looked, 40A.
What does that mean, I wonder?
This would be the rated current of your house / apartment / mobile home. Basically, the higher that number, the more stuff you can have plugged in and running at one time.
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W=VA.
for a given wattage 110 will need twice the current as 220. 220 will fry you less.
Not true, assuming that your body has the same resistance to electricity regardless of voltage, if you get an electric shock at 220V, then the current passing through your body will be twice what it is at 110V. I have heard it said that 60Hz is more dangerous than 50Hz, although I can't remember whether that is true or not. The biggest difference in reality is the different earthing standards in different parts of the world.
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I see that it has been snowing in in parts of India.
Mmm. Isnt India supposed to be a hot place with no snow?
Wonder where it will snow next? Barbados?
All this global warming is great. If this is the result of global warming then wonder what it will be like with gobal cooling. Lol lol lol.
Bring it on I say!
You do realise that it snows in India every year, don't you? They have some very tall mountains in the north of India.
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Sorry, can't help you there, I am apple illiterate
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Snowfall data from NOAA Rutger’s Snow Lab for April is in.
It ranked high enough to make the cold season (November 2012 to April 2013) average the HIGHEST in the record (back to 1966).
Must be all this "man made global warming melting all the snow" LOL making it snow the most on record since 1966!!!! LOL LOL!
Do you understand the difference between precipitation and temperature snowdude?
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You can just plug in a wifi router on one level, then use a range extender / repeater type thingie on the other levels Dumbstick. Very handy for your portable devices.
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I would personally go for a wired connection - the cost of a few network ports around a new house is really not going to break the bank and allows for much higher speeds than wifi.
As far as connecting up your fridge, smart fridges will be able to send alarms if the temperature goes up (imagine your wife forgot to close the fridge door, and when you got home all your beer was warm!)
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If you'd doing from scratch, is there much of a difference in cost between a plate with 2 sockets and 4 sockets?
I would imagine not, but that's just a guess.
Cheaper to put in 2 x double sockets than a 4 socket - a 4 way socket costs about 5 times what a double does - at least that is the case here in Australia - mainly because they are the most commonly used. There is almost no price difference between a single socket and a double either.
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Its a special place is Perth
I still don't understand why the locals pronounce it coburn.
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I have cartels, like them a lot, also moderately stiff good all mountain bindings.
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Makes a difference too if it is for a dedicated tv/movie room or a general purpose lounge I suppose. Dedicated home theater room then bigger, maybe stick with a 40 - 50 inch for a normal lounge.
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I didn't say that the TV series isn't good, I actually really like it, but the books are better.
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The books are better
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Stiffer boots / bindings will generally be a bit more responsive, particularly for carving, softer boots / bindings allow more flexibility so better for jibbing / jumping. My personal feeling is that moderately stiff boots are the best all mountain option for me - stiff enough to carve well, soft enough to muck about in the park if I want. The Ions I currently wear rate 8 / 10 on the stiffness scale and I haven't once thought "I wish these boots were less stiff."
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My favourite is and now for something completely different
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Flights to the Americas with Air New Zealand, Qantas, Cathay Pacific and possibly other airlines, allow economy travellers up to 2 pieces of luggage at 23kg per piece as standard.
LED lighting
in General off-topic discussions
Posted
In theory, you are right, but in reality, you will find that every transformer will have a small current flowing. To be technical, for a transformer coupled device the loss depends on what is called the leakage inductance of the primary coils of the transformer. This is essentially the amount of magnetic flux in the coil that is not connected into the secondary.