JOULE is the quantity of energy
WATT is the quantity of energy used or supplied per unit time (also called power)
http://www.mhi-inc.com/Converter/watt_calculator.htm
We often encounter power and energy separately: cars and motors are often priced by horsepower (power); light bulbs are often priced by their output watts (power); natural gas is sold by energy content namely therms (energy) and of course the supply-demand situation; electricity by kilowatt-hours (energy); furnaces are priced by kilowatts (power) and temperature capability Kelvin (K); and air conditioners by tons or BTU's per hour (power).
Power is oomph! Power is the amount of energy that is converted in a unit of time.
Expect to pay more when demanding higher power.
When you purchase a energy conversion device (say electrical energy to heat), the device will often be rated by its "power". This enables you to calculate how much energy you will use (and pay for) by simply multiplying the rated power multiplied by the hours used. Each electric unit you pay-for, is normally one kilowatt-hour (one unit). When you pay for units, your US electric utility bill contains price for units used during normal usage and price for units used in a "demand penalty" condition. You should always carefully watch this penalty number, and contact your electric utility provider to find ways for reducing this "penalty" charge.
The calculator(s) below will help you to convert energy from one unit to another and if you know the time over which the energy is delivered, it allows you to calculate the power. And if you wanted to get a feel for the amount of energy used in terms of equivalent amount of gasoline burnt or in terms of how much ice the energy would melt-you can do that also. Have fun!
Remember Energy is always conserved (such conservation is known as the first law of thermodynamics). Entropy is not. When you posses energy with the lowest entropy you posses the most useful form of energy for conversion to work. When you convert energy from one form to another, you create entropy (almost always)- and when you do, the process is called irreversible (because you generate entropy). In ideal cases you may have a process that does not cause any irreversibility, and consequently no entropy is generated. Electrochemical processes and processes where work is converted to work are such processes, but often not quite a 100% reversible.
Anytime heat is produced and transferred from one temperature to another (i.e. across a temperature gradient)- the process is irreversible because entropy is generated.
Phone (513) 772-0404
Fax (513) 672-3333
Email Us
MHI (Micropyretics Heaters International Inc.)
750 Redna Terrace
Cincinnati, OH 45215, USA
513-772-0404 phone
513-672-3333 fax
Delivering quality since 1991
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