What exactly is the power rating of a particuar applicance signifying and why's it given as a range instead of a single value? e.g, my kettle says it has a power range of 1850-2200W. Thanks.
2006-12-08 09:09:01 · 9 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
What exactly is the power rating of a particuar applicance signifying and why's it given as a range instead of a single value? e.g, my kettle says it has a power range of 1850-2200W. Thanks.
It doesn't have multiple power settings and the reason I'm asking is because I used the kettle for my specific heat capacity of water project, used 2200W as the delivered power and wasn't sure whether this would contribute to a significant error in the the calculated C because 1850 is 15% less than 2200W. From what you're saying though, the UK use an AC supply, so if V is constant (which I'm not even particularly sure it is) then P will vary and I was right to consider it a source of error? (Sorry for confusing things further!)
2006-12-08 09:24:28 · update #1
The designers will have used a nominal power setting (probably 2kW in this case).
In Europe, supply variations (-6% to +10%) are allowed around the nominal voltage of 230V. This gives you (1880-2200W).
If you use a stabilised power supply such as provided in some labs then this will minimise this, otherwise you have to accept it as experimental error.
2006-12-08 20:45:40 · answer #1 · answered by Anonymous · 0⤊ 0⤋
the power rating of any electrical device is an indication of how powerful it is. a 10 kw motor will give a lot more power than a 1kw one.
same with a kettle - higher wattage-more power-faster boiling.
the power in watts is equal to the voltage x current flowing i.e. at 240 v 1kw = 1000w.divided by 240 = it's about 4 amps (you can get your calculator out) It is given as a range because the voltage in any country will never be steady all the time (things being turned on and off all the time cause that as the generating equipment struggles to keep the grid going. in this country they are allowed a variation of either side of 240V
2006-12-12 11:34:57 · answer #2 · answered by Anonymous · 0⤊ 0⤋
You may find fairly large voltage variations from place to place, hence the wide range of power rating (Power being calculated relative to voltage). It may also change by small amounts in the one socket you use depending on other system loads.
Also, as the element heats up, it resistance will change slightly and so the power will change slightly.
Since the biggest change comes from the supplied voltage (anywhere from 220 to 260v), you will probably have a fairly constant power during your experiment but you just wont know what it is.
If your application requires an acurate power reading, you have little choice but use a power meter.
2006-12-10 08:21:02 · answer #3 · answered by Poor one 6 · 0⤊ 0⤋
Power is the the current multiplied by the voltage. The voltage can fluctuate depending on the power source, and this causes fluctuations in both current and power. The makers of the kettle are just letting you know it can operate safely within the specified range to allow for these fluctuations.
Edit: Just out of curiosity, does it have multiple power settings? Well, I suppose if it were that obvious, you would not have asked.
2006-12-08 17:13:42 · answer #4 · answered by DJL2 3 · 1⤊ 0⤋
In the UK the mains electrical supply voltage is 230-240v, this is where the variation in power comes from. There is ~ a 1A difference between 1850w @ 230v and 2200w @ 240v.
Oh and Pleeease note V*I IS NOT power its apparent power (VA). To calculate the power from this you need to know the power factor (pf).
2006-12-09 15:38:04 · answer #5 · answered by Anonymous · 1⤊ 0⤋
When power is generated for technical reasons relating to phase angle difference between the phases this makes a difference to the efficiency of the potential usable power.
This portion is called Watt-less Current and is just waste.
Unity Power Factor is !00%and the lowest accepted is 85%
The difference of your kettle reflects the differing usable current.
If Generating Stations out-puted at 100% efficiency then their Carbon Footprint would be greatly reduced.
2006-12-09 03:24:19 · answer #6 · answered by Anonymous · 0⤊ 0⤋
The voltage for any wall outlet is specified as a range, typically +/-20%. US voltage, for example, is considered to be valid anywhere from I believe 98-145V (don't quote me, but it's close). Since your kettle has a specific resistance, the power will vary with voltage, thus giving you a varying power range based on the wall voltage at your house at any particular given time.
2006-12-08 17:45:50 · answer #7 · answered by EE dude 5 · 0⤊ 0⤋
you got it. the power is proportional to the voltage. P=V.I.
the voltage in each property will vary over the course of the day depending on your neighbours and your use of power. incidentally a drop in voltage also causes a drop in current so a small voltage change can cause a larger power drop.
P=V.I :
SINCE I=V/R
P=(V x V )/R
Put some numbers in and see.
mg
2006-12-09 08:52:42 · answer #8 · answered by Mark G 2 · 0⤊ 0⤋
2200w is what it draws from the mains while it is boilding, when it reaches an ambient temperature it draws 1850wats.
2006-12-08 17:12:11 · answer #9 · answered by stone 3 · 0⤊ 2⤋