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8/12/2019 Physics Word14

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Renewable Energy

Lab 3 Gas Laws and Heat EnginesFall 2010

Name____________________________Name____________________________Name____________________________

Introduction/Purpose:In this exercise y! will test sme " the as#ects " the ideal gas law !nder cnditins "

cnstant #ress!re$ cnstant tem#erat!re$ and cnstant %l!me& 'hen y! will b!ild a heat

engine t li"t a##les& ()ay$ nly small nes&

Apparatus: *asc Gas Law +##arat!s$ rd stand$ water baths at %ari!s tem#erat!res$stainless,steel tem#erat!re #rbe$ gas,#ress!re sensr$ rtary,mtin sensr$ *- and Lab *r

inter"ace$ 2.0 gm and 1100 gm masses$ 3. grams attached t light thread$ #lastic syringes

and t!be c!#lings$ cnstant,%l!me brass gas %essels&

Theory:The Ideal Gas Law

'he e/!atin " state "r an ideal gas is writtenPV nRT= 1

whereP gas #ress!re 4in *a r N5m267V gas %l!me 4in m367n n!mber " mles " gas7R a cnstant 48&31 95ml,:67 andT the absl!te tem#erat!re 4:el%in6

;hen a##lied t a clsed system i&e& ne in which the am!nt " gas is cnstant thisgenerates three "am!s relatinshi#s between the three state %ariablesP$ Vand T

1& 'he Law " -harles and Gay,L!ssac states that when a gas is )e#t at a constant pressure$its %l!me is directly #r#rtinal t its tem#erat!re&

2&


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Renewable Energy

;hen #sitined %ertically n a rd stand$ additinal masses may be #laced n t# " the#istn #lat"rm t change the #ress!re in the cylinder& 'he #ress!re sensr meas!res theabsl!te #ress!re in the cylinder$P$ in )*a&

+s the #istn m%es$ the %l!me " the cylinder changes$ alth!gh it can be held "ixed by !sing

the setscrew at the t# " the cylinder& 'he %l!me " the system cnsists " the %l!me " thecylinder #l!s the %l!me " the al!min!m can and the air hses& 'here is a millimeter scale nthe cylinder that allws ne t directly meas!re the cylinder height$ hcyl& 'his height will bemeas!red !sing the rtary mtin sensr& Frm this height$ the %l!me " air !nder the #istn$Vcyl$ may be determined "rm

V r hcyl cyl cyl = 2

2

'his meas!rement will N('$ hwe%er$ be the same as the ttal system %l!me$ V& >atherV V Vcyl= + 0 3

;here V0is the %l!me " the al!min!m can and air hses&

V0can be determined i" the #ress!re in the system is )e#t cnstant by allwing the #istn tm%e "reely with ne side always at atms#heric #ress!re$ and %ary the tem#erat!re byimmersing the al!min!m can in water at se%eral di""erent tem#erat!res&


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Renewable Energy

I" the %l!me is !nchanged d!ring the transitin$ the change is re"erred t as isovolumetric&

In s!ch a case$ since dV 0$ it is b%i!s "rm e/!atin 2 that n wr) is dne&

I" the #ress!re remains cnstant$ the transitin is isobaric& In this case$ e/!atin 2 sim#li"ies

t

WPV 3

where Vis the change in system %l!me&

I" the tem#erat!re remains cnstant d!ring the transitin$ the transitin is isothermal& In

s!ch a case$ !sing e/!atin 1$ P nRT

V= $ s that e/!atin 2 red!ces t

===

if

V

V

V

V V

V

nrTdVV

nrT

PdVW

f

i

f

i

ln ?

I" n heat enters r lea%es the system d!ring the #rcess$ it is called adiabatic& In this case$

we can !se the "act that *Bis cnstant where .

3"r mnatmic gases and

C

."r

diatmic gases$ t integrate e/!atin 2 ab%e&

"ere&s the Iportant Part:

In a heat engine$ a system !nderges cyclic transitinsthat$ e%ent!ally$ ret!rn it t its initial state& In this case$the wr) dne d!ring ne cm#lete cycle may be "!ndsim#ly "rm the area enclsed in theP-Vdiagram " thecycle&

The Incredible 'ass Lifter Engine

D!r lab gr!# has been a##rached by the Newtn +##le -m#any ab!t testing a heat

engine that li"ts a##les "rm a lwer #rcessing cn%eyer belt t a higher ne& 'he engine y!are t ex#eriment with is a real thermal engine that can be ta)en thr!gh a "!r,stageex#ansin and cm#ressin cycle and that can d !se"!l mechanical wr) by li"ting smallmasses "rm ne height t anther& + schematic diagram " the #rcess is shwn belw

heat

cool

-M+M


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Renewable Energy

'he !se"!l wr) #er"rmed by the engine$ calc!lable "rm the area enclsed in the P-Vdiagram$ sh!ld e/!al mgy$ the wr) dne n the a##le&

Procedure:

A( Law of )harles and Gay*Lussac +)onstant Pressure,-( !nt the gas law a##arat!s n the table& !nt the rtary mtin sensr n the rd

stand& ' c!nteract the inherent weight " the #istn$ and t allw y! t meas!re the#istn height$ hcyl&$tie 3. grams t ne end " a light string and tie the ther end " thestring thr!gh the small hle in the t# " the #istn& *ass the string !# and %er the #!lleyn the rtary mtin sensr with the 3. g mass hanging dwn the ther side&

.( '!rn n the *- and lad the -harles Law Lgger*r tem#late& >ecrd the %al!e "P,which is dis#layed in the meter windw at the lwer le"t " the cm#!ter screen&

'he Lgger *r tem#late a!tmatically !ses the rtary mtin sensr and E/& 2 t "ind the%l!me " air in the cylinder& Hwe%er$ it is gd techni/!e t als recrd the cylinder%l!mes by hand "r e/!ilibri!m in each tem#erat!re bath& 'his can be dne by recrding#istn #sitins directly "rm the scale n the cylinder wall& 'he tem#late als recrdstem#erat!re and #ress!re& a)e s!re t !se the absl!te tem#erat!re :el%in in y!ranalysis&

'he tem#late will ma)e a time series recrd " y!r data& D!r gal is t bser%e thisrecrd and determine times where the system is in e/!ilibri!m with the tem#erat!re bath&D! will be extracting %al!es "r the three sensrs '$ B$ and * "r a #int in time that y!

thin) re#resents e/!ilibri!m& D!ll d this "r each tem#erat!re bath&

( -are"!lly twist and detach the cnnecting hse that leads t the #ress!re sensr& 'his bringsthe inside " the cylinder t atms#heric #ress!re& Lwer the #istn t the bttm " thecylinder& 'his mechanical @ering is im#rtant beca!se the encder @eres itsel" at thebeginning " each data,cllectin r!n

0( Jtart cllecting data nw by #!shing the -llect b!ttn in Lgger *r& 'his ser%es tdc!ment the mechanical @ering #eratin in y!r dataset7 b!t y! ha%ent sealed thesystem reattached the hse yet$ s this #int wnt be !sed in y!r B %s& ' #lt&


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Renewable Energy

1( Next$ seal !# the system and establish the am!nt " air that will be s!bAect t the ideal gaslaw& >aise the #istn !ntil it is near the middle " the cylinder$ and then reattach thecnnecting hse&Record the position of the piston here and the !alue fro your digitaltheroeter +air teperature,( +lternati%ely$ y! may !se a rm,tem#erat!re waterbath "r this initiali@atin ste#& D! may need t re#eat this initiali@atin ste# later i" y!

s!s#ect y!r system has lea)ed any air d!ring the

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