How many watts does it take to do a certain task ? (need a list)

Power (measured in Watts) is a measure of energy (Joule) per unit time (second).

There are two useful formulae depending on whether you are working with electricity or not.

Electricity :

Power = Voltage x Current

So a 1 watt device could be powered by 10 V @ 0.1 A, 1 V @ 1 A, 100 V @

0.01 A, etc. If you were using a 9 V battery and required 0.45 W (watts) then you would have to draw 50mA (milliamps).

Non electrical :

If you have a device that produces usable energy eg a motor or heater, you can work out what can be done if you know the wattage of the device. You may also need to know the efficiency.

A 100 W heater, will produce 100J of energy per second. If you were warming a room, and knew the heat loss per second, you could calculate the size of the heater required to maintain a constant temperature.

A 100 W motor, with an efficiency of 50% (ie half the power is lost in friction, heating, noise) will be capable of 50J per second. You could calculate the acceleration this would provide to a model car.

I've made such lists in the past. Here are some examples...

0.001 watt powers a digital wristwatch

0.25 watt powers an electric clock motor

5 watts power a small night light

60 watts power a desk lamp or a laptop computer

200 watts power a personal computer or good-sized stereo system (note that I'm talking about AC consumption, not audio output power)

1000 watts power a window air conditioner

2000 watts power a portable electric heater

10,000 watts power a house

These are rough estimates. Others can chime in with better ones.

A-Level (high school) text books often give a table like the one you seem to want - although not with 1 watt resolution. They usually illustrate the idea with things like {light bulb, hair dryer, television, train}....... Other than that try

Andy

--
--
The above email address is whitelisted.
If I don't have your address already, I wont see your message.

Michael A. Covington wrote: : I've made such lists in the past. Here are some examples...

: 0.001 watt powers a digital wristwatch

: 0.25 watt powers an electric clock motor

: 5 watts power a small night light

: 60 watts power a desk lamp or a laptop computer

: 200 watts power a personal computer or good-sized stereo system : (note that I'm talking about AC consumption, not audio output power)

: 1000 watts power a window air conditioner

: 2000 watts power a portable electric heater

: 10,000 watts power a house

: These are rough estimates. Others can chime in with better ones.

The human body consumes an equivalent of about 200 Watt...

--
Uwe Bonnes                bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

--
Behind a 2000 Calorie diet, about 100 watts.

--------------- A Watt is a Joule/second. A Joule of kinetic energy is given to a kilogram when it is accelerated so that it gains 1 meter per second each second for a distance of a meter.

2 Joules would be 2 kilograqms, or 2 m/s, etc.

A J = (1 kg-m-m/s/s) and a W = (1 kg-m-m/s/s)/s = kg-m^2/s^3

There are lots more equivalencies that can be discerned directly from the physics of the factor label metric system. TAKE PHYSICS!!

-Steve

--
-Steve Walz  rstevew@armory.com   ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!!  With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public

70,000,000-100,000,000 W powers the QE2!

120,000,000,000 W powered a Saturn 5 First stage (150,000,000 HP)

Uwe Bonnes schrieb:

Hello,

at rest, it is only 70 to 100 W. But Lance Armstrong may consume up to 1800 W.

Bye

He probably *IS* taking physics. Hence his curiosity. Having seen all the formulae, definitions and equations he can stand, he wants something he can hang his hat on to give a conceptual understanding of the magnitude of the entities he's dealing with.

Bob

I always thought that the most a human could produce (other than in short bursts) was less than 1 HP and more like a 1/3rd.

: Uwe Bonnes schrieb: : > : > The human body consumes an equivalent of about 200 Watt... : > : Hello,

: at rest, it is only 70 to 100 W. : But Lance Armstrong may consume up to 1800 W.

Oops: 2000 kCal/day * 4.2 Ws/Cal /24 h/day / 60 min/hour /60 s/min is around 100 Watt.

Thanks for the correction.

--
Uwe Bonnes                bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

And this info can be found at device ratings, or computed from voltage/current ratings.

--
Chaos Master®, posting from Brazil. REPLY TO GROUP!
"People told me I can't dress like a fairy. 
 I say, I'm in a rock band and I can do what the hell I want!" 
                                                   -- Amy Lee

Note: this e-mail address goes to /dev/null.

Thanks to all who have provided me with meaningful answers that I can ponder and look up further, to get more knowledge in the subject.

I have recently purchased what I feel is an excellent book, written 'at my level'. The book is: "Basic Electricity" by Van Valkenburgh, Nooger & Neville, Inc.

I may come across something in the book I don't understand, and therefore post my question(s) here.

I'm actually overwhelmed at the number of responses, and insightful info, my thread generated.

Thanks, George

1 horse = 7.5 men. Sounds about right.

I'll second that.

I'm guessing it was supposed to be in reply to someone else, but the wrong message was replied to.

-Ed

-- (You can't go wrong with psycho-rats.) (er258)(@)(eng.cam)(.ac.uk)

/d{def}def/f{/Times findfont s scalefont setfont}d/s{10}d/r{roll}d f 5/m {moveto}d -1 r 230 350 m 0 1 179{1 index show 88 rotate 4 mul 0 rmoveto} for /s 15 d f pop 240 420 m 0 1 3 { 4 2 1 r sub -1 r show } for showpage

I'm still scratching my head over this as well.

Cheers!

Sir Charles W. Shults III, K. B. B. Xenotech Research

321-206-1840

seem to

voltage/current

Yes, but be careful with that - the ratings on the labels are often maximums, and don't represent the typical load presented by the product in question. Add to that the possibility that for many types of products, you'll have the little matter of power factor to consider if all you're doing is looking at the voltage/current specs.

Bob M.

Yes, but then 1/7.5 horses = 1 man. This may or may not be correct, depending on the man and the portion of the horse in question. Note especially that certain classes of "man" (e.g., members of Congress, or politicians in general), can often be equated directly with certain parts of a horse...

Bob M.

>