Remembering the Sign Conventions for q and win AE = q - w Students often have some difficulty in accepting andlor remembering the sign conventions associated with the mathematiealstatement afthe First Law of Thermodynamics, AE = q - w . I have devised a quasi-historical rationalization which emphasizes that early thermodynsmieists were primarily interested in improving the efficiency of steam engines. These workers were concerned with two ouantities: heat inout and work outout. What convention could be more natural than to assign positlvc value* t o t h e t w ~ ~ ~ t r - ~ n e ~qoantitws. s ~ ~ r e L Armed ( w i t h this devm.studentr r a n then d e r l w c the. .ign f,.r w , r k dew on t h e s).ten> and heat IIN h\, r h r s w t m h n t h n q n t w c , . Francis P. Gasparro Department of Biochemical Sciences Princeton University Princeton, New J e r s e y OR540
Volume 53,Number 6.June 1976 / 389
