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Home Q & A Board Science-Related Homework Help Physics
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o2484680@rtrt o2484680@rtrt
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11 years ago
I intend to heat some quantity of water (say 1 liter) by applying electrical energy to a resistance. How much power is needed. From the power, I will deduce what electrical resistance is neccessary for using say a 120 V electrical network outlet.
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#1
11 years ago
That depends upon the efficiency of heat transfer from the electrical device, and upon the time it takes to heat the water.

A low power device can heat the water to the same temperature as a high power device, except that it takes longer.

You need to better define the constraints of your experiment:
Starting temperature of the water.
Desired end temperature.
How fast you want to change temperature.
Material characteristics of your heating unit.

Done.
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smileyladysmileylady
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#2
11 years ago
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#3
11 years ago
Electrically speaking you would not want to draw much more than 1000watts from your 120V Outlet so a minimum resistance should be V^2 / P = 14 Ohms or so.   10 Ohms would give you 1440 Watts at about 12 Amps.
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#4
11 years ago
The definition of a BTU (British Thermal Unit) is the amount of energy required to raise the temperature of 1 pound of water 1 degree F.  There are 3,412 BTU's in 1 kilowatt/hour.

As a previous poster said, you need to define starting and ending temps and some other variables, perform some conversions based on the above and you should have your answer.
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