Lecture_05_02_08_2012

# Lecture_05_02_08_2012 - The First Law of Thermodynamics y...

This preview shows pages 1–7. Sign up to view the full content.

The First Law of Thermodynamics on Reifenberger Ron Reifenberger Birck Nanotechnology Center Purdue University February 8, 2012 Lecture 5 1

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
First Law of Thermodynamics Overlooks the fine microscopic details (which in many cases are irrelevant). Describes the conversion of one form of energy (heat) into other forms Important Consequences: Conservation of energy Allows estimates of maximum efficiency of energy conversion Completely General! (not just ideal gas) 1 st Law 2
he Effect of Heat The Effect of Heat “ istributed” Distributed Energy http://mw2.concord.org/public/part2/heat/page8.cml 1 click 3

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Statement of 1 st Law (1842) E int = Q + W E int E int represents the distributed energy in a closed system. It can contain contributions from a variety of sources like thermal, chemical, etc. Sign conventionl 4
he “system” Universal Appeal! The system The “system” can be a collection of matter in any form, separated from its surroundings by real or imaginary boundaries. The system may be a biological cell, the contents of a test tube, the gas in a piston, a thin film, or a cup of coffee. How you define a “system” depends on the problem you want to solve. 5

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ign Conventions When using the 1 st Law, it’s important determine the proper signs Work (W) has a sign associated with it: f work is done ON a system it is assigned a positive sign Sign Conventions to determine the proper signs If work is done ON a system, it is assigned a positive sign If work is done BY a system (external work or work on the environment), it is assigned a negative sign Note: This sign convention is consistent with definition in mechanics in which work done on a system (eg lifting a box) increases the mechanical (potential) energy of the system. By analogy, positive work on a system eat (Q) also has a sign associated with it:
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 24

Lecture_05_02_08_2012 - The First Law of Thermodynamics y...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online