GCE A Level Physics 1976-2003 Topic 17 current electricity

GCE A Level Physics 1976-2003

T0PIC17

Current Electrici乞

yJ个丨丨丨丨

r

、 ich st泛、/l】 bct、 vccn1、

ltcl11cnt dcscribcs t丨 vO points in∶

lc clcc(lic pOtcntial cⅡ viI^c that cE1】、、ˉ 1ˉ a currcnt? ics

ffcrcncc

/〕 LΟA

`\

1丨

lc fOrcc rcqui1 bct、^/ccn thc丨 )()ints

cd tO Iη

OVc a unit positivc chargc

迢土

1hc】

ˉ ati(〉 Of thc cncrgy ch、

si丨)a(t)d丨 )cl\vcen (hc pOi丨

lts t0

thc currcnt C thc ratio of thc po`vcr Ciissipatcd bc(、 (hc currcnt D thc】ˉ atio of thc powcr dissipa1cd bctwccn1he poillts ro thc chargc lnovcd vccn thcρ oints to

//〃//

C

/O

厂

r' )'Jl' tltct'

pr()t( inll

t,

C

J76/II/17;Nl84/Il/17;J97/I/13;J2000/I/16 2、 Vl、 ich onc of dlc follOⅥ rclt、 1iol1bctxvcen currcnt`and applicd丨 char:1ctc1ˉ istic of a geH11ani1llll diOde?

y

Tcn:;i:

/ing graphs best rcprcscnts[11c ).d, y∫。 r thc lk)∶ˉ、Ⅴard

oΕ

ll rtrt N77/U/17

A surgeol'currentl-lows througha filarnentlalnp r.vhen is it i'ilstswitched The leason the surgeis that on. lbr w h c n t h e l a r n p i s s w i t c h e co n, t h e f i l a r n c r r t s c o l d l i l t n d i l . s r c s i s t a r r cic n r u c l i l c s s t h a r na t i t s w o r k i n c s ternpcratLlfe. the mains voltagernay be at its peak value when the Iarrp is switched and the currentwill then be greater on t h a ni t s r . m . sv a l u c . r n a i n ss w i t c l r c sa r e s p r i n g - l o a d e c ln d l n i t k e s u d d e n n c o n t a c tr i o t a l l o r v i n g i m e l b r t h e c u r r c n tt o i n c r c a s e, t gradually. t h e p l r a l l e l c o n d u c t o r sn t h e m a i n s c a b l e a c t a s a i c:apacitor anrl thi.scapacifordischargcs itself tluough the f'ilunrcnt. the fllarnentis a,-roiluncl this acts as illt indLrctance whiclrproduces lurgee.nr.l'. it J78lll/19 Which of the f'ollowinggr:rphsbcst lepresents the currentvoltagcclralacteri,st o l' a sclniconductor iodc'/ i cs d

、/丨、 1c

B

B

C

D

9Λ

g T1’ t( Hov

J76ilU24 3 A r e s i s t o rr i l ' r c s i s t a n c c . 0 k Q h a s a t h e r r l a l c a p; t c i t y l ' 1 o 5 . 0 J K - 1 .A p . d, o l ' 4 . 0 i s l p p l i e da c r c . si s{ o r I 2 0 s . I l ' t l r c V t rr:sistor thennallyinsulatccl, llnal risc in tcnipeurtur,,: is thc i.sA 8× o B 32~× C 96 .× D o8 3K E 96,K J77/lI/18 l4 oK l3 oK丨K o 20 rr.'ltr^oC n

10.. r,thin

I

The rcsisttrrce l'tungstcn incrcases ith incr-crrsirrg o w tcllpcl'iltut'eAs:r rcsult,thc rcllrtioubclwecrr currerrt, . tltc 1, l ' l o w i n gi n t h e t u n g s t c l lt- i l a r l c no l ' a r rc l c c t r i cI:a n t pa r r ctlh e t y, potential dil'l'ercnce, bctwccnits cnd.s of'thc lbrnr is

voltage

N78/II/24

Fl

tt b

l 7 C u r r e n tE l c c t r i c i t y

184

1A’

Physics TOpical Pape1

l7 CLrrr

GCE A Level Physics 1976-2003

A l r i g h p o t e n t i a l i s a p p l i e d b e t w e e n t h e e l c c t r o c l e so f a h v c l r o g e nd i s c h i r r g et u b c s o t h a t t h e g l i s i s i o r

r i s c c lI,l i c c t r . o n s t h e r r m o v e t o u, a r c l st h c p o s i t i v c c l e c t r c t d ca n t l p r o f o n s t o r v a l c l st h e r r c g a t i v e c l c c t r o d e . l n c a c h s c c r l n d, 5 x l 0 r 8 e l e c t r o n s( e a c h o l ' c h a r s e - 1 . ( r x l 0 I ' ) C ) a n d 2 x l O r E p r o t o n s p a s s a c r o s s - s e c t i o no f t h e t u[ ' r e . h e c u r r e n t l l o r, v i n g T in llrc disclilrgc tubc isA 0,16A B 048A C 0,80A l/ D 1,12A]【|44A J80/Il/23

F o r a g i v e nt h i c k n e s s h c r e s i s t a n cb c t u ' e c n p p o s i l cc d g c t, e o n l ' a c eo l ' t h es a r n p l ( s l r o r v s h l d e di n F i g . I ) i s s c A I] C D E proportional .r2. to proportional to,r. irtdependent .r. of inversely proportional to.r. i n v e r s e l p r o p o r t i o n ao, v 2 . y tl

/

N81/II/21

I1,q batteryis connccted seriesrvith a 2 Q rcsistctr in and a switch lrs shou,nin Fig. 2 bclorv. A volttnetercoltnectcd across the batteryreads I 2 V rvhen the srvitch is open but 8 V u, h e nt i s c l o s e d . i

'Iensilc

//It/ l-1 en it is

stririnmay be nrcasurcd tlie changeirr clcctrical by resistance slr'alngutrye. strairr ol'a gauge A corrsists ol'l'olclcd 1 - i r r e e t aw i r e r l o u r r t e d n a l ' l e x i b l e s u l a t i nb a c k i n g h e e t, n l o in g s lirmly attached the specirnen, thatthe strainin thernetal to so u, i r ci s a l w a y si d e n t i c atlo t h a ti n t h e. s p e c i r n c n .spec丨 men

Fg i。 2

s cold/orking cn thc.Il.C,llts1r

s t r a i ng a u g e

Whatis thc intcr!lal rcsistance Of the battery?

Whcn the strainin the specirnerr increascd, resistancc is tlrc ol' thcrvirc A B C t l c c r e a s c s .c c u r r s t l r c l c n g t hi r r c r e u s c sn d t l r . 'c r o s s b e u scctional arcadecreases. tlecreases, because lengtlrdccrcuscs tlre cross:rnd the scctional areaincreases.

A〃 B lζ C43/Ω D 4Ω E 6Ω

ζ飞2 2

J82/【

I/17

udden crease tas a rrouglr

12

In t11e circuit show11 in Fig, 3 bclow, dle resistancc of thc tungstcn nIaIη Currcnt can bc varicd by lη cnt Ia:η p L incrcases 1o飞 cans ofthc rheostat,`ith tC:llpcraturc. TIlc

i r t c r e a s e o r d e c r e a s e . se p c n d i n gu p o n t l r e r e l a t i v e s d nragnitude the changes lengthand cross-sectional of in are?i, irtcrcases, because the lcngtli dccrelses linclthc crossscctiontllrelt i ncrcltscs. i r r c r e a s e b, c a u . stc e I e n g t hi n c l c a s e ns d l h c c r o s s sc h .n s e c t i o n l la r e a e c r e a s e s . d N 8 0/ l l/I 9 ',J 9 l l l 1 3V of pO、/.Thc povv/cr is transnlittcd(hrough cab丨。 vcr at a potcn(ial cs

D l0tance t/Il/| () urrentE

A gcncrator produccs I00 k、 di{1℃ rcl1cc of10k、

of tOtal rcsistancc5Ω

Fig.3 W h i c h o n e o f t h e l b l l o w i n g g r a p h sb e s t s h o w s h o w anrmeter reading varies l with the voltrneter readingV?

IHovv n1uch poⅥ/er is dissipated in thc cablcs?

A-_>_ rlia no

/rrq:rv

50W V V V J81/II/17;J87/l/20;J93/I/14;J96/I/13

B 250、 C 500、 D 50000、

10 A .sarnple resistive ol' rnaterialis preparcd the f'onl of a irr t h i n s c l L r as ca bo f s i d e . r . rl

VⅡ/24

Fg i。 1

N82/II/17

Papcr

1Crcl Ectiiy 7urlt lcrct

185

'A' Physics Topical Paper

GCE A Level Physics 1976-2003

13

u, l, A b a t t t: r f i s c o t t t t c c t c r t o a u t t i l i r r t l tr e s i s t l r n c c i r cX\ ', a r t d ir t h u c i t, . l Y o l ' t l r c$ ' i| e i s c l i l ' t l ) c r li r s s l r u v v r t t t l t r:c i r c t t i t irlv. r l i r tu t - lttt t l t c l

、Ⅴh11t is thc rrltioΛ 9O;Ι 72 C 5,4

po、

λ/c∶

ln

R i n c i r c u i(ti licˉ Ii l1 ci⑴ 1t I(

o}

porvcl iri[i

^

D3 O E 1,8 J85/l/17

I;

t W h i c h o n e o 1 ' t h c{ o l l c u ' i n gg r a p h ss l r o r v s l u t ut t - r .ctlrlcllt a c l e r r:; i t yv/a r i c s l o n gX Y ' l .

,se 1 7 S o m e c a r l y e l c c t l i cl i g h t b u l b s u s c d c a r b o l i l ' i l e t r t e t r t t h, 0 r c s i s t a n c c s{ ' n, l r i r: hd c c r c i r s c da s t l t c i r t c t l r p c r i t t t t I c ' incrcasccl. graphs bcst l.clrrcscttts Which o{' the i'ollorvitrg thc wity in which/, tlte curretlttliroughsuclt ii bulb, woultl it'/ across dil't'erence upon v, tirepotential depend21^t

、

E

∶ uc' 0r

人

∧

J}Izarn

B

C

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al

p o i n ts )

J86/I`14

XD E J3I1;8//3 8/V7J8I1

14

、 VI1at is dlc cOnductancc of t、 cross-scctional area⒕

、vh c c)f lcngdl` and unifolˉ∶ ade of nlatc1ˉη ial or rcsistivityρ?

1η

o 1 8 f n e r e s i s t a n o e f a c e r t t t i nc i r c u i t e l e m e n t i s d i r c c t l y proportionalto thc current passingthrouglr it. Wlien tltc is in currcntis 1.0A the powerdissipated tlie eletnetit (r'0 W. rvhenthe culrent is ritised to What is the powcr clissipated 2, 0A?Λ 3、 0 B 60V,V C 1、 2 VⅤ D 24、/、 E 48VV N87/I/13

Th‘l C )⒈ C

A

∠ p`

:号 C竿 D古 E毕J3H1;8/I1 8//8N4I/8

A '

J E

蘑 A 5

/ d c i r c u l a r p l i r . s t i c i s c e r l ' c l i a t t r e t e t ' rh a s t l t l r c t a l s L u c l s 1 9, q r, v i r c3 . 0 0 t t t l o t t g, t t l ' u t t i l i l t ' t t tc r o s s - s e c t i o n aill l ' e a E r r p i l i r r r r r l y s p a c e di r r o u t t d i t s c i r c u r t t i ' e[ c l l c e . l c h s t u d c a r r i e s o 2 . 0 0 I n n r 2,l t a s a c o t t d u c t i l t l c c 1 ' 1 . 2 5 S . W h a t i . s t l r e a i i c h i t r g c 1 7 .T h c d i s c i s t l a t l c t o t . t l t i ' t t c b o t t t i t s a x i s a t 7 . r w tl r c s i s r i v i to l ' t h ct t t i t t e r i a> 1 ' t l r ei r c?[ l S= l Q - r] y ol' lhc r c ' v o l r - r t i o n st e r s e c o t t d . W h a t i s t h c c q L r i v l l c t t t c t t r t ' c t l t l lotating chnrgcs'/A 5ˇ 3× 107S l07S

23、 nuc∶ shc

A R{l

tttl/ 1t ncl npq

D E

Ind n7rc1 ndnpqJ85/】/14

I: 8,3× C O,80S D 2,4S El9,×

16 0S

N87/I/14

' 1 6 l ' h r c c i c k: n t i

c ac c l l s c a c h h i i v i n ga n c . t ' t r . lo.l ' 1 . 5 V l t n c la l below, tlte shadedarca o{' in ol'2.0 f) ttrecontrcctcd se'rics 20 ln tlie cliagrartr an oscillosctlpc itttcrnalresistatlce consteurt through tlte electron beam which is repres(lnts scctiol-l a r v i t h a 4 . 0 A r e s i s t o R, f i r s t l ya s i t t c i r c u i t( i ), n n d s e c o n d l y r at ancl generatecl nelr P, clel'lected acceleratcd Q, anclfbcLrscd r . si r rc i r c i r i ( i i ) t o ': r tI t . I" h c t t l - rrc t t t t t l t i tllls g l l s t

、I、厂al

B

|

E

( Circtrit i)

Ci1cuit(ii)

l7 Currcrrt61..1v'lc:ity

186

'A' Plrysics Topical PaPet'

17CuI

GCE A Level Physics 1976-2003

c o v I l o r vd o c st h c el e c t r i c r . l r r c n tf ' t h eb e a t n a r ya l o n gl ' Q R '?;\ Bs//7 5l1

't'24\n

valucat P, Q ancl Il. It hls thc silrlrc t s l I t d e c r c u s cls' o n rP t o Q b L r b e c o t n ev e r yl a r g ca t t h c p o i n tR . fl'onrP to Q, (hen incrcirscs rcuclrtlre It clccreascs to v s a r n e a l u ca t I l a s a t P . I t i r r c r c r" r s[c r c t u, e c n i r n d Q, t l r c r rr c r r r l r i nrs( ) n s t l r l ) t -s P ' l-rorrr to ll. Q It incrcases ll'onr I'to Q tlrcn decreascs reaclrthc to valueat R as at P. stlrne N87/l/6

an electrostal.ic rnachine, belt of rvidthrr,,having surface a c h a r g c c n s i t y, t r i l v e l s '" v i tv c l o c i t yv . A s t h c b e l t p a s s c s d o h a point,all lhe chargeis rcrnovcdand is carried u\.vay ccl'tililt l t sa n c l c c t l ' ic u r r c t r tW h a t i s t h c n t a g n i t u d t t t ' t h i sc u r r e r r t? . c D E rvr.,2o tlyl,t,2ciJ89/1/13

Λ lvvσ B望 C望⒐坠

C D E

)ste I,h )raturc丿 rcscnts、 vou{d

’夕

2 5 n n e l c c t r i c as o u r c ew i t h i n t c r n a lr e s i s t a n c e i s u s e d t o l r opcratea larnp of resistance Wlrat fraction of tlre total 11. powcris deliverecl the lanrp? to A c y l i n d r i c a lr n c t a l w i r e, o f l c n g t h/ a n d c r o s s - s c c t i o t l i l l R R, C, arca$ has rcsistartcc conchrcfance resistivityp ancl _Λ D o c o n d u c t i v i t y ' . W l r i c h o n e o l ' t h c f o l l o w i n gc x p r e s s i o nl s r b r厂 o isvnlid? AGR Br1\-c

t) ltl

\PR

D孺 E罕J88/I/丨5

"`一h~ R R~"

E

~ R

C

J89/I/14

26 two squares, and Y are cut ll'orn tlre same sheetof lη X/, of thickness The lenethsof the sidesof X and Y are`and 2/ respectively.t

ctal

5I1//4 cctly 91c t1 0、、′。 cd 1o

2 2 A c o n t l u c t i n gi q u i c ll ' i l l s l a c y l i n d r i c a lr n c t a l c a s e to a depth .r as shown in the diagram. The resistance ctlvecn b the case ancl thc rnetal rod is A B C D E

metalrod

T叫上

cylindrical metalcase

rr}Yt)

//3 I1 area e tl丨

plr:portional to.r2, proportional to.r. independent,r. of proportional0 . r . inversely t p i n v c r s e l y r o p o r t i o n a l,r2 tct

insu丨 a‖ng base

What is thc ratio#- of the resistances betweenthe opposite R. shaciecl

l'aces X ancloi Y? ofN88/I/13Α l一 4Β

c⊥ l

23 An electric current l'lows along an insulatecl strip PQ ol' d m e t a l l i cc o n d u c t o rT l r c c u r r e n t c n s i t yi n t h e s t l i p v a r i c sa s . s h o w ni n t h c g r a p h .

D 2 l N89/I/10;J2000/I/14

27 A tlrermocolrple connectecl is across a galvanometer of resistrtnce Q. Onejunctiorris itnmersed lvaterat 373 K in 30 and the otlrcrin ice at 213 K, The e.rn.f.of the tltertnocouple in betweenthe is 90 pV lor eaclr I K dil'f'erence temperature junctions, resistance 6 Q. is andthethermocouplc will llow in the salvanometer? What current A R C l.8pA 250 prA 300 ptA D ll1,5mA l,8mA N89/I/13∶ J92/I/16

丨/4 1

aΓca l !S SCd

distancealong strip from P

W h i c h o n e o f t h c l b l l o w i n g s t a t e n r e n t s u l d c x p l a i nt h i s co variation?Α B C DΕ

The strip is narrowcrnt P tharr Q. at The strip is narrower Q thanat P. at gradicnt the alorrg stripin uniform. The potential 'l'hc thanthc currcntlit Q. currcntat P is grc?rtcr T l r e r e s i s t a n cp c r u n i t l c n g t ho l ' t h cs t r i pr s e o n s t l t n t . c N B 8/ rl/4

2 8 f n e c u r r e n t/ l l o w i n g t h r o u g h v a c0rnponent aries with the potential V difibrence across as it shown.

l7 Currcrrt Electricity

187

'A' Physics Topical PaPer

GCE A Level Physics 1976-2003

¡ª¡ª

、 lich、/丨/?

d

( t r ': l r -\ hl - .| r - ( l

r e p r e s c n tIs o v vh er e s i s t a n c e v l r i e su ' r t h 31 A s t r r c l c ri r t q i r c n u s r - ' u l cb lo x c o n t l r i r r i r r r t ' o r rc l l c u r t R s t lg e c l c c t r i c a lr l c u i t . c H l v i n g L u k c n s c r i c so f ' c u r r c n ta n d v o l t a g cr e u c l i r r g sh c a t, plotsthc cLrrrcnt-voltrrge student charactcristic bclolv. current/mA0 y O/

w c l

A

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ovo29

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V

N9Ⅳ I/16、丨Ⅴ licll circ11itis n1Ostlikcly to bc cncloscd、 Vithin thc bOx?

A gei)erator, n,ith outpltt p 0 w e P and output vO丨 r conncctedto a l'actoryby c a b l c s l ' t o t a l o ,clsc 1 Rcai lts

tage l么

is

A

匆

o

2B⒍

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ganerator (P,VI刀 2、 'I1L、、 tis thc pO、 vcr in丨 )ut

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∶

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c? y

∝

——彐[[-::∶ i1一

一^ D已lc pa!∶ e}

t( 1h)t c

ˉta 1(c J

: P一咩| )钅C P一咩 )`

Λ P

咩D

’一

P -

R一2

D¨世石 N92/【/14=°~N94/I/15

s、Ι:)}∶

咩E

2 R

P -

A

30 fnc iiiagrarn shows a rnctal f ilarncnt lalnp connectecl irr series with an amnteter,lratteryand a variableresistor, A hiqh rcsil;tancc voltnteter conrrccted is across lanrp. thc

32 Trvo rviresP anclQ, circli ol'thc sanrelcngth zrndthc sal11c 'fhc nratclial, connected parallclto a battery. are diaIη in o f P i s h a l ft h a to f Q . What tl'itction ol'the totalcurrcntpasse.s throughP?A 0.20 1; O,25 C 03,3 D 0.50

ctcr

D

36Th(N94/I/16tC1I V丨

33 A c c l l o f i n t e r n a lr e s i s

t a n c r i s c o n n e c t e d o a lOad Of e t

In aCr

re.sisiance/?.ce" l丨

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厂

`kˉˉ 0:「

W l i i c l r g r a p h r e p r e s e n t sh e v a r i a t i o l r0 1 '/, t h e c u r r c n I t tlrrouglithe lurnp,rvith tlre potential clil'lbrcncc across I/ it?

ttl,/t/ t/:-L+

A

B冖冖〃〓

c〓

R Energyis dissipated the loacl,but sornetlrerrnalenergy in 'l'he is also waste irr the cell. d cl'ficiencytil' suclr an arrangcnrent lkrurtcl is ll'url thc cxltlcssiorrν3 7

t/VtJ0

c n c r g y i . s s i p l t citrlr t h c l o a c l d c n c r g yd i s s i p a t eid t l r ec o r n p l e t c i r c u i t n e、η of the lbllowing givesthe cll'iciency this c a s e? V丨 ich inΛ土

P f咖〔 W!| n ul n

E,l

lA t/t/

l,/ o--_-l[7 C]urrcnt Elccrtricity

l/,/ t

R

B卫

c厂 R+r

D

/lR+厂 J95/I/14

N93/I/丨 2

188

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P l r y s i eT o p i c l l P a p c r s

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GCE A Level Physics 1976-2003

t丨d l(∶ )

, (l、丨 c

tlrc 34 tl'hich graph bcst lcprcscnts u,ay in u,hichtlrc cun'cnt1 c ls the clil'l'cre V ncc r t h r o u g h t h e n r i s t o r l c p c n c rupon potential i a c r o s sl ' l A tlI/l/

38 Ttrc cliagranr shorvs relatirrrbetwecnthe clircctcr-rr-r'cn[ thc/ in a certainconductor lnd tlte potentialdif'f'crence ucr.os:; i/ y c i t . W h e r r< 1 . 8V, t l r e u n ' c nits n c g l i g i b l c .

C

/

t/

t/t/

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zkN5I1 9//4

//rlA

l/

35 T l r c d i a g r a r . n. s h o w s l l r (: c t a n g L r l l rb l o c k w i t h d i r l c n s i o r - t sr ', 2 . r ' l i r t d3 . r .

0

Which statement is about corrductor correct? thc AElectrical conlact can brr nrade to the block betwecn oppositc p n i r . s l ' l l c c s ( l i r r e x l m p l c, b e t w c c l t t l r c l ' a c c sl a b c l l e d P ) . o Betwecn whiclt two l'itccs would tlie maxitnutl clectrical

-

B C D

rcsistancc obtained'/ be//:丨 5

A Il C D

t、 )CΠ lc1er

P the laceslabelled the taceslabclledQ the llccs labclledlivhichcvcr pair of Iraccs is is the lesistance the sanrc,、 used

I t d o e sn o t o b e y O l r m ' sl a w b u t w h e n V> 1 . 8 V i t s is lesistance 4 Q. It does not obey Ohm's law but rvhen V= 3 V its is rcsistitnce l0 Q. l t o b c y s h m ' sl a w w h e n t r/> 1 . 8V andwllcny=3V O i t s r e s i s t n n cs l 0 Q . ic I t o b e y s l r r n ' sa w w h e n y> l . B V butits rcsistancc is O l J98/I/14 l10tconstant.

J96/I/14

//【丨6

36 fne rcsisturceol'a tlrclrnistolclcclcases:;ignificantly its as tempcratulcncrcascs. r the tlre Which grlph best rcpresents wrty in wlric:h current/ r:polt the potcntialdil'f'erence V in the thcrrnistorclepencls

39 Four srnall concluctors, on tlre cdgc of an insulating isc of radius d r, are eachgiven a

charge ol' Q. Thc liequency of r o t a t i o ro f t h ed i s ci s/ .r Whiit is tlre equivalent electric current at tlre eclge tlie disc? of 4()

J Of

rcro.s.s it? ARC D

i\

4Qf

B

t+/l-_l\-.l\l n*

i

C犰rσ D罕N98/I/14〃o

/lv

I'.rf

1-;

./vJ 9 7 l t l l 4; N 2 0 0 0/ lI/3

"0

"0

4 0 r n e d i a g r a r ns h o w s a,ηodel of an atO【η in which t、 electronsnrove round a nuclcus in a circular orbit rl~hc ls s. 1ˉ 0 clectlons cclrrplete R!llorbit"l1.0× one

clgylaⅡ

3 7 P l o t o n s n a p a l a l l e l e a me a c ht n o v ca t a u n i l b r r n e l o c i t y ', v r b i thLrs lbrrling i) currcllt/. The chargeon cacli protonis a. prcscnt lcprescnts Which exprt:.ssion tlrc nunrbcro{' 1)rolons tltc irt unit lcngth of thc bcilrn'/(You rnay wish to consiclcr n u n i t so l ' t l r cc l u a n t i t i ci s v o l v c c l . )

electron

electron

′、、 hat is thc cu1

rcnt

causcd by thc l11otion oF thc cIcct1

o1、 s in

A⊥L,

:⊥r’ V

c⊥r’

D⊥N7II 9//4

thc Orbit? A 16,× 13A 04 13I 01A

C 1,6× D 3,2×

I1/4

B 32 .×

10丬 A lOˉ4A J99/I/15

’丨C丨r

1 7C u r r e nE l e c t r i c i t y t

189

‘ A’ Physics Topical PapC了

GCE A Level Physics 1976-2003

4AclOcmfⅠ 1 clr,,,\′、 hicll statcn∩Λ 'r′

了 dlⅤ ei cntis c()rrcct?

c sacag(t)1ctra I hrcP(1nXCn丨

cr辶 ic

It i

嫘 7r‘ f丿 DcⅡ

丿 nc/冫@、 l丫` ,

(b丿 tion in1hc cxtcrnt、 l cilcuit is厂 1)c,口

、Ⅴ|ly is i1thtl1,i Il1hc SI systcl11(){′ bc clc{1ncd11siIl:∶ thc cqtIt1tion

units、

po、\`cr CI1nnot

hc cncrgy dissipt、

I; Thc cllergy dissiPatiOn wit丨 C The cxtcrnal resistancc is fg, D 'Γ hc total cncrgy clissipatiOn in thc ccll r、 circ11it is″ g. N99/I川

lin1丨 lc ccll is丿

I、 thc cxtcrna丨 d 3

p)c=Oeta df℃ (wrptnil i{

rl c】 c× c

c1r)l? 1r(lt

丨

2]

N8I/ 8/ll

4ll A potcntilldil'l'clcrrce clrivcs cun'crtt throtrglt/ V i.t ti,l tl t h t:l ' i l a n r c ro t ' a t o r c: h u l h, b

菇 2∧

thin lill111ˉ l utlll and is Iη

Csistor in a sOhd-s1rltc circuit has a t丨 adc Of nichro!11c Of rcsistivity|0^6Ω ablG bct、

lickncss Iη,

( i i ) a p i c c co f i n t r i n s i c e m i c o n c l u c t o r, s Skctclr onc fbr cachcasc,to shou,horv/ dcpcncls uraphs, on 1./lts V is incrcasecl l'rom z.efo to lr valuc which cau:ics gni heati .si l'icant rrg.

C)亡 lCulatc1hc rcsistanccs avaⅡ、∶ 1 1111n2arca Of11hη 1

^/ecn oppOsitc cd.Jes Of

rr`丿 ifit is squarc shapcd, t S ctnua (′9丿 if i i r c a g l I

53(′

,0ic a klgtsii wd, 2tms s )l 1 ts ic

J76/I/543A gcncrator suρ instaHation by po、 tcpwrls a ha i tccbc i pO【 h oe ot s et n h als s rp vhcrc 1 、/is thc l)Otcntial diffcrcncc at thc gcncrator outl)ut,

Why clothc graphs dil'f'er shape'/ in

6]【 N89/IⅡ/s

pIics a fixcd powcf to an clcc"ict1|^/cr lhles ofΓ illitc rcsistancc Sho、 )ˉin丨 I toa∧ 1hat/ 1l` o/,

49 An elcctrickcttle is ratcclat 2.0 kW when operatingon ir 2 4

0 V s u p p l y .W h a t p o w e r w i l l t h e k e t t l ea b s o r bi l ' t h e is to sLrpply rccluced 220 Y? t3l N89/tII/7cr

(′)

Tllis rcsult suggcsts tl、 by a su"ablc choice OF gcnc∶

at lossCs Can bC rcduced indchnitclyˉ t11()rp.d。 l)iscuss b!ˉ ic{=丨 y、 vhcd、

50 (a)

lanrpis ilarked 240V 60 W. CalcLrlate A I'ilrrncnt (i) t h c c u r r e n t l r r o u g h h e l n m p w h e r ti t i s w o r k i n g t nolrnally, tll

t h i si s p r a c t i c a b l c .冰 4钅

N81/I/7

×'亻`丿

A - altttniniurrt5

J F

S= stccl

(ii) ihe rcsistancc f the liimp when it is working o nolrnally. tll (iii) 'l'hc resistancc the larnp is lirund to be less ol' whcn it is not lit tharrwhen it is rvclrking norrnally. Sketclr the current-voltage<;f characteristic the lllarnentlzrmnon thc ttxesin F i g .5 . current/A

{)

Fis.4 A n e i e c t r i c i t y u p p l yc a b l et: o n s i s to 1 ' as t e e lc o r eo f a r e ao l s s o c r o s s - s c c t i o n5 0 r n m 2 r v i i l t s i x o i h e r c t i n d u c t o r s f aica arotrnd alurniniurnof the samecross-scctioniil arrilnged . o i t ( l t r i g . 4 ) F i r r dt h e r e s i s t a r r c c' a 1 2 0r n l e r r g t h l ' t l r e c u b l c . ol ri x niLr[Rcsistiv itics:stccl,9,0x I 0 (]m, alurrri rr, 2.-5 I 0-8Qrn.l J82tIl6 e l S U s i n g a n e l e c t r i cc l r i l l .i t t a k e s 1 5 0 s t o r l a k c a h o l e i n i r piece cll' brass ol' nrass0.4-5kg. During this proccss, thc averzlgcpowcr dclivercclto tlre clr-ill('rorntlrc elcctricrly rniiitts is 300 W. FIow lnrrch electricalenersv is uscd in d r i l l i n gt h eh o l e ' l I l ' l O%, o f t h e c n e r g ys u p p l i e d o t h e d r i l l a p l t c a l s s h c l t i r r t a t l i c b n r s s, l i a t i s t h c i n i t i a lr a t co l ' r i r; e l '[ e n i l t e r a t uoc' t h e w o rl rrctal'/ ( S p c c i l ' i c c a tc a p a c i t y f b r a s s 3 9 0 J k g I K r . )= h oJ84/I/ll

o

240「 ig。5

Vo"age/V J94/II/3(ρadtm n ic

{-otart)

54

sr,-tC

5( 1‘

J st丿 t、

1 tcculinl1klgcag@c rct C h q:1o i1i1 hre,u rn∫

USui^iv

`.丿 (′冫 Calculatc thc cha1 ciI c1!it i11a ti∶ llc of60s、

[l]ge which passcs eadl pOint in a vhcn thcrc is a cu" cnt of0,76

SKCI arttl 1C. ill

mA,

[2] N95/II/4(paIˉ t)

4 6 n c c l l h a se . n r . l '1 . 5V a n c il n t e r n ar e s i s t" a n0 .e Q . C r l l c u l a t c 52An clcc1ocⅡ . l c5 V, lrkcd120V,4O、 ght bulb is nlΙ rvhcnthc ccll is r:onnccterl uu cxtclnal thc porverclelivcrcd io cu11、 tc thC Curlcnt ill this buⅡ,xvhcI1ope1ˉ (‘`丿 Ca丨 . 2, 5{> r c s i s l o r W h n t i s t h c v a l L r c l ' t h c c x t c r n ar c s i s t i u t ci c' o l l 10sIp 2V1p丨 y‘ n l h c p o w c r c l c l i v c r c i ls t o h a v cl i i n u x i r r r u rv a l u c '/[61 Cuncn1= i88/lll/4

h,ating on a

tltcA[21

I 7 Currentlllectrici ty

190

' A ' P h y s i c s o p i c a lP a p e r T

l7 Cur

GCE A Level Physics 1976-2003

(b)l I〈)】l t

D c s c r i b e h r e e d i l ' l c r

c n r v a y si r r n ' h t c l r n c r g yc u n b c 5 5\ l ' h a t d o y, t, l ru l r c l c r s t u n d y t t c b ( a) r e s l s t u n c e . t r a n s l ' c r r c ' 1 l ' o n rt h c i i i a r l e n L u ' h e n i t i s o p e r a t i n g cJ nonrrally. 1b) rcsrstivity, 16l(r con<lLrctivity. (i) (ii) N81/【 lI/5(part)

2 1丨}Ⅱ// l

) ( r: ) I l ' t h c l i g h t b r r l bi s n o w ' c o n l t c c t co ll 2 4 0 V s; L r p l t t y tr il w i l l u, o r k l i r r p c r h l p sr t n h o u r: r su 1 6 0W b r r l bl r c l o l c: 5(t (a) i t s f i l a t n c nb r c a k s . t

I)cl'inc ll"tet'ortlorrlt, the jortla anc,lthc rr,'a11. Show thatdel'ilting lre volt iis a joulc lter coulontb t i s c c l u i v a l c r rtto d c l ' i r r i n g t a s a w a t t p e r a l r p e r e . i

(i)

F I o w w i l l t h e r e l a t i i, c n t p r l r t a n co l ' t h c a n s w c r s i e y o u h a v eg i v e nt o ( D )c h a n g c l r c nt h eb u l bi s n r r r w o n t h i si n c r e a s c v o l t l g c ' l d

N 8 9/ l l l il 0 ( p a r t );N 8 2/ l l l/ 3 ( p; l t )

t-5l

(ii)|o sn廴 lsCs

SLrggcst reason u,liy thc bullt carropenltc{br so ir l o n g a t i n r eb e l o r ci t s f i l a t r e n tb r e k s, a t 3 J 57 Octlnc tl'tevolt, and distinguishbetwcenelectrontotit,c forcc N97/tr15 ancl differcnt:e . N82/lll/3 (part) ltotcrttiol. 58 Dcduccl'romfirst principles exprcssfor the ratc at which lin hcat is gcnerated a circuit o1'rcsistance in whiclr a in/l c u r r e n t/ p a s s e sS t a t e c l e a r l y t h e b a s i c d e l i n i t i o n s y o u . eniploy. A voltrneteris connectcdacrossa variable resistanceR, which itself is in series with an amrneter and a battery.For one value of/1, the readings are 1.00 V and 0.25 A. For another lue of R, theyare0.90 V and 0.30 A. Calculatethe va c.rn.l'.ol' the battery,its internal resistance, and tlre two values R. of you State any assumptions makcccrncenrirrg meters. thc The valucof R is now acljusted that it equalsthe internal so resistance the batterv, the rate at wlriclr hcat is of Calculate generated. (u) (b) in Lhe biittery, in tlrc rvhole systcnr. N84/lll/3

53

(u)

[61 II丨/ 5

D c s c r i b c,i n t c n r s o l ' a s i n t p l c e l e c t r o l lr n o c l c ll,h c d i l ' l ' e r c n c c c t w e e n a n c l e c t r i c i r lc o n c J u c t o rn d l r r b a clectricalinsulator. tZ) State (i) (ii) w t w o m e t a l s h i c ha r ec o n d u c: t o r s, which is a concJuctt>r, onc t.ron-rnetal

(b)ol1 a

t1丨 c 1J 3/III/7

( i i i ) o n e s o l i dw h i c l ri s a n i n s u l a t o r . (c)

t3l

Air is normally an insulator. Hclwcvcr, can bc ntade it to condr"rct uncler certain conditions. (i) S u g g e s to n e c o n d i t i o nt l r a t c o u l c lc a u s ea i r t o conducclectricity. t (ii) Suggestone hazard which rright be associated w i t h t h ec o n d u c t i o o f e l e c t r i c i tiy a i r . n n 12)

「 kiIlg丨:] Iκ lng[] l lcss (Ing`agc Cs ln

(d)

D e s c r i b eh o w t h e i n t

c r i i l l r e s i s t i t r t r,oc a c e l l t r i a y b e 'f Give . . . . . . . . . . . . . . . . s. . . . . . cleternrinect. thc theoryof'your nrcihod. . 'fhc v a r i o u s l e c t r i c ac i l c u i t si n o p c t r t i o ni n n c u r r n a y b e e l ( i i ) t h e n u m b e ro l ' c l c c t r o n s n r i t t c d e r s e c o n d r o r n p f c 'fhey/ are c o n s i d e r e d o h a v e a c o r n b i n e dr e s i s t a n c e 1 . t the cathode. r. supplied a battery ol'c.nr.1'. and internalresistiince by E nunrbcrpcr secorrrt ...s-|[-1] ( t t ) l l ' t h c c l ' l ' i c i e n c y o l ' t l r cc i r c u i t sr n i t yb c c l e l i n c d s t h c a n D\ilU4 ratio o1'tlrepowcr dclivercdto Lltecircuits to the total showthat Long Questtons llowcrdissipatccl, t i n l ct u k e n rurl) inre 54 Distinguish betwecn the terms potentirtl di.ffercncaand electromotivcforcc. Dcfinc thc units in rvhich tlrey urt: tusuully mcirsured. t4l Civc threc cxarnplesol' systernsin r.vlrich clrrrent is not Givc clirectly proportionalto applied potentialdil'l'erence. sketcli graphs showing the lbrm ol' each/-V relationship g a n dg i v e s o t n ee x p l a n a t i oo l ' t h el o r r no l ' c a c h r a p h . n[(r] 'i'lie cul'rent/ throughu ccrtaindcvicc i.srclatecl thc p.d. to V acros.s by the equation it/=rr(ehv-l)ll iI

In a czrthode-my tubc, there is il curfenfol'1.50ptA in t l r c v a c r r u n r e t w c c n t h e c a t h o c l en d t h c a n o d e . b l Calculate 59 (i) the tirne taken for a chargeof 3.0 C to be transf'crred

Wtrat do you unclerstancl tlre tenns potentidl di.fference by andeIecI rorno ivefo rce'! t

1l=R/(R+r). ( b ) S k c t c h a b e l l e d r a p h s n t h e s a m ea x i s l o r R t o s h o w g l o how 11and tlrepowcroutputvary rvith/1. Mark tlre axis w i t h t h ev a l u e l ' r ' . o (c) I ' l c n c e,o r o t h e r r v i s e, e t e r r r r i n e 1 w h e n t h e r e i s t d poweroutpLtt rnaxirnurn fionr the battely.

tllll tl ). ll)ral

t-l lrt)

w Il'thc stnrter otor of a car is operated lren the headm light.s arc su,itched on, thcy are scct.r rlirn. Explrin this to observittion. N8-5illl/ll 60 Del'ine resistiince resistivity. and (o) Calculate thc resisLance a niclirontc wire ol' lengLh ol' . 5 0 0 r r na r r r c l n r r i c ( c1 . 0r t r t r g i v c n t h a t t h c r e s i s t i v i t y n l r o l ' n i c h r o r ric l . l x 1 0{ ' O n i . s 'A'

I;'21t)er

wlierec= l0-aA andb= 40 V-r. When tlredevice connectcd is o, . l o a b a t t c r y l ' e . n r . l '1, 5V, a c u r r e n o 1 ' 0 . 1 I ' l o w sC a l c u l a t c t A of l h c i n t c r n a r e s i s l . a n c e t l r ch a t t e r yl.l g c= 0 . 4 3 . 1 l t8l N77/ilr/3

1cretEctiiv 7urn lcrct

191

TopicalPaper Plrysics

GCE A Level Physics 1976-2003

(i)

(ii)

how you rvoulcluse a potentiontetcr Dc.scribe to 64 (tt) (i) r r r a k ct r t a c c L l r i t ld r . t c l ' n t i n l t t i o l nt h c r c s i s t i u t c c i c c ' ol'tlris,irc. u (ir) E x p l a i r rr v l i y l t r o b l e r n s n i g h t l r r

i s ci n t r y i r r gt o r d c t e r n - r i nh er e s i s t a n co l ' t l t i sw i l e b y r r c e s u r i n g tc e tlrecurrentthroughit and tlie potcntial di{'l'crence a c r o s st L r s i n n r o v i r r g - c olin e t c r s . i g l

Dcl'inct,lcctt'ir: potcntie!diJ.fcrcnr:e statc tlrc anrl S I L r n iitn u, h i c ht i s r n c l r s u r c d . i U s e y o u r d c l ' i n i t i o nr r ( i ) t o s l r o r vt l r a t P, t h c i r o l[ ) o w c rd i s s i p u t i o in r u r c . c i s t o rl ' r c s i s t a r r c/c i s giverby r`P〓

、丿 r‘

一R

(b)

S t a t e a n d c x p l a i n o n e l c l d i t i o n u l p r c c u u t i o nr, v l r i c: h u,oulclbc ncededto obtiiin iin lrctcunltc valLrclix' thc r c s i s t i r n co 1 ' a w i r e o f t h e s l n r o d i n r c n s i o na s a b o v c . c s but rnade coppe of r. ( R c s i s t i v i to l ' c o p p c= 1 . 7x l 0 t f ) n r ) y r N86/IH/ll

w h c r c V i s t l r c p o t c n i . i l r lc l i f ' l c r c n c c: l c r o s s t h e i

resistor.

t5l

A b a t t e r yo f e . m . f . E a n d i n t e r n a l r e s i s t a l r c e. i s r connected sericswith a lesistorol' r'trsis(ltncc as in/?, s l r o r v nn F i g . 7 . i

61

D c l ' i n e p o t e r t t i a l d i J J e r c r t c t: ', r n r c . s i s t u t t . ' cD e r i v e a r r cl . cxpressior.r Ihe rate at wlrich thcrnralenergyis gcnerated lbr i i r a c i r c u i to l ' r e s i s t a n c e i n w h i c ht h ec u r r e n i s/, R t 14] De.scribe how a voltmeterrnaybc calibrafcd one particLrlar at readingby an electricallrcatingnlethocl. rel'erencc tlrc lly to t h e o r yo l - y o u rm c t h o d, x p l a i nw h y v o l t r n e t e rc a l i b r a t e id e s n this way cilnlrotbe said to have beencrlibratedin telms of t h e b a s eu n i t so n l y . 7]【 A c e r t a i n v t i l t m e t e rh a s a r e s i s t a n c e l ' 1 5 0 0 O . W h c l t o connectcdto a battery,the vol(mctcrreads 2.90 V. Whcn a lesistor ol' rc.sistalrce 1000 Q is then conneoted par:rllel in witlr the voltnrcter, reading thc dropsto 216 V. Explainwlry the readirrgchangesand calculateall you can about the battery.Ⅱ[6]N87/【/ll (i)

66 1丿

Fig.7 Give expressions, ternrsctl' r and/? fbr in Ii, ( l ) t l i ec u r r c n/ i n t l r cc i r c u i t, t ( . 2 ) t h e p o w e r P n d i s s i p a t c di n t h e o x t e r n a l resi stor. (ii) The batterygenerate.s total pr;wer P1..Sliow that Pn the fraction is givenbyP-l

(l,丿

(c丿

‘ 2rrJ丿 ( i ) (ii)

Dcfincresi.rlottce, Write down an ccluation whicli relates re,sis!ance and rcsistlvir.y. Identily all the syrnbols in the equation, t3l

f*= RPr R+r

t6l

k″

Calculatcthe re.sistance ntetrcof a coppervrirc of' per diarnetcr 0.050mrn and rcsistivity1.7x 10.'N nr. l2l f) J90/lll/2 (part) (i) D i s t i n g u i s lb e t w e e n h c e l e c f r o r n o t i vl e r c e o l ' a r t b c c l l a n d t h c p o f e n t i a lc l i f f e r c n c e e t w c e ni t s b terrninals. A c e l l o f e . r r . l ' .O a n d i n t c

r n a l r e s i . s t a n c e i . s r connected n rcsistor to ol'resis(zurceas slrorvn R ilt Fig.6.

A car batteryof e.rn.l'.l2 V a i i d i n t e r n a l r e:; i s t a n c c 0 . 0 1 4 Q d e l i v e r si r c u r r e n t o f I l 0 A w h e n I ' i r s l connected the stnrter to motor. (i) Calculate ( I ) theresistance the starter of nlotor, ( 2 ) t l r c l l ' a c t i o no l ' L h c t o t a l p o w c r i v h i c h i s dissipated the battery. irr t.5l (ii) Al'tcr prolonged use,the internarl rel;istancc the of batterymay increase. Stateand explain how the pcrlornranccof the battcry is afif'ected by an incrcase theintenral in re.sisLancc. L4l J93llill3

63 (u)

(ii)

65 (a) A potentiiil difference ol'9.0 V is causingelectronstol'low througha steelwire so that 1.0 x l020 elcctrons a l)ass pointin thewirc in (r0s. Cirlculate (i)Fig“‘

thc chargc rvhichpas.se.s point in (r0 s, tlre

( i i ) t h c e l e c t r i c u r r e n iIn t h e w i r e, (iii) tlrercsistance the wire. of Slrow tlrat V, the tcrrninal1;otential dil'l'crcncc ol' t h ec c l l,i s g i v e nb y[61

y= FFt’R厂+

16丨 N91/IⅡ/4(palt)

S k e t c h g r a p h sw i t h l a b e l l e da x e s t o s h o r v h o w t h c currcntlhroughthe wire will vlry with the p.d. acro.s.s i t i l ' t h c t c l r p e r a t u ro f t l r ew i r c e (i) is keptcon,s[ant, 'A'17Cul

I 7 C u r r c n tE l e c t r i c i t y

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c丨 l 1 c

( i i ) i n c: r e a s a s t h ec u l ' r ' e nn c l c a s c s . e it r\ c: o p p ew i r c o f a r c ao f ' c r o s s - s c c t i o n . 8 l 0 -" r -1 r h a sl c n g t h0 . 6 7r n . (i) C a l c u l a t ch c r e s i s t a r r c c ' t l r cr v i r c .( l l . c s i s t i v i t y o1 t o l ' c o p p e= l . '/ x l 0 * 8O t n . ) r t3J⑴ Fig。 9 ci)

’|c、t l J’i k s

heating element

I丶

^叽

( i i ) W l r e nt h e c o p p e rr v i r ei s s u t r j e c t etd a p a l t i c u l r t r o s t r - c . s ss t r a i n l ' 0 . 0 l 2 i . s r o d u c c dn t h c r v i r c . p a, i o ( I ) Stiitcrvhatis rncant .r/rz.r'.r by .ytt'trirt. by and

0刊

(〃丿 suggcst I、 avcragc po、 pcIˉ iOd oFtiIne,

lη OrC sui1tlblc IIlcans of ct)nt1ˉ vcr output ()l∶ thc hcating c|c nlcn1 ovcr a 121J95/III/4

OⅡ illg tllc

l s a s

l2l(2) S h o w t h a t t h e l l ' a c t i o n a l c h r t n g ei n t h e l l r c a o l ' cross-section f the wire is -0.012. Assurlrc o tliatthc lotal vtiluntcrcnlrirr.s naltcrcd. t2l u ( l a l c u l a t e t h c l c s i s t a r r c co l ' t l r c i v i l c r v h r: r ri t

?,

(3)

s 6 7 ( u ) U s c c n c r s y c o n s i d e r a t i o tt lo c l i s ( i n g u i s bc t rvee ri h e l e c t r o r l o t i v c' o r c e( c . l l . l ' . ) a n c l l t o t e r r t i l td i l ' l ' e r c r r c e l l (pd) LJIr a I

h a st h i ss t r a i n f 0 . 0I 2 o

3]丨 N94/I1I/3

(b)

A c c l l o 1 ' t:, r n .If . a n di n t e r n ar e s i s t l i n c厂 is Connectcd l e to a resistor lesistance as shownin

Fig.lO. oi R,

66rrl丿

polcntinl I)r:l'inc dit'l'ercncc.

tl I

7 e e rf,丿 l l ' t h e e q u a t i o n=/ R i s u s c dt o c l e{ ' i nre s i s t a n c w,h y i s i t n o t t h e n p o s s i b l et o u s o t h e s a l n e e q u l t i o n to del'ine dillcrcnce'/ L2l llotential O n e c l e r t r c n t l ' a n c l c c t r i c c o o l< c lh u s a r r/ - V o cliaractcri.stic shownin Fi'r. 8. asIi:g。

nlaI

that

A voltrneter of infinite resistance is connec:tcd

purallel rvitlrtlie rcsistor', (i) s F i C o g r y i g . l 0 a n di n c l u d e r r t h c c i r c u i ta s r v i t c l r o t l r a t t h c v o l t m c t e r u l a y b c u s e c lt o m e r r s r r r e cithcr the e.rn.l'.I ol- tlre ccll or the terrriniil potenti dil'f'erence al V.

[6]fln cc

f: s i t

( i i ) S t a t rr:v h e t h ctrh es w i t c hs h o u l d e o p e t to r c l o s e d b u,hr:rr rrtca.suring l.0 50 I00 150 200 250

t h ec . n r, f, t h c t e r m i n ap . d . l

2.

∶is h[5) ft丨 1c/丨 l t c` an

Fig. tl (i) E x p l a i r rh o i v t l r c c h a r a c t c r i s t i s h o w s l h a t t h c c resisLancc the r:lcrnent increascs witlr p o t e n t r l a of dil'f'erence. t3l E x p l a i n i n t c n r s o[ ' t l t e r r t o v c r n c r otl ' c h u r g e t l r p a r t i c l e sw h y t h e r e s i . s t a n ci e c r c a s e s i t l i n w potential di{'['elcncc. I3l

( i i i ) D e r i v ca r c l a t i o n e t w c e ni, V. r'ancl currcnt/ tlic b I i n t h cc i r c L r i t, l-5l

(tr"t,:.lt) .196/lll/4砥 8(‘J丿 Del'irre potantialdifferclu:eanclthe volt.

tzl

[1 4∫/ I3 Ils to rons

(ii)

(l,丿 A b a t t e r yo 1 ' e . n t . f .9 . 0 0 V a n d i n t e r n a l r e s i s t a n c e

8.36 Q. to 0.50 f) is connected a resistolof resistanco Deternrinc (i) (ii) t h ec u r r e n itn t h ec i r c u i t, t h c p o t c n t i acl l i f l c r c n cA ( i r ' o sh c 8 . 3 6O r c s i s l o r, c ts[61

(iii) Use thc grirphto estinratc potential rcnce tlre clil'{e w h i c h s h o u l db e a p p l i e dt o t l r c e l e r n e ni t1 i t i s t o Iril.",c resislance 30 Q. A of t3l ( i v ) W l t a t w i l l b c t h c c u r r c n ti r r t l t c c l c: n r c n t h c n i t w has a rcsistiurce 30 Q'/ ol' Il I

( i i i ) t h c p o w c rs u p p l i c do f h c 1 J . 3!6 r c . s i s t o r ' . t )(c)

t6lLhe rOSS

(v)

W l r a t w i l l b e t h c p o w c r o l ' t h c e l c m c n tr v h e ni l I r a sa r e s i s l" a no fe 3 0 O? c ' tIl

( r l ) W h y i s i t n o t s e n s i b l eo c o n t r o lt l r c p o w c rt o i r h c a t i n g t c l c r r r c r rs, r c l a . s h e o n c l ' o rt h c c l c c l r i cc o o k e ri r r f r: ), tr r l h y t h c L r s e) l ' e i t h c o l ' l h ec i l c u i l sr r tF i g .9 '/ i r l4l I 7 Currerit Electricity犭 93

E x p l a i n w h y t h e p o t e r l t i a lc l i f f c r e n c ei i c r o s s t l i c t e r n i i n a l so l ' a b a t t c l y i s n o r m a l l y l o w e r t h a n t h e w h a t t e r y ' s . r n . f .U n c l e r h a t c o n d

i t i o ni s t h e p o t e n t i a l e c l i f ' f ' c r c n c ic r o s sn b i r t t c r y ' st e r m i n l t l se r p t a l l o i t . s i c 'i 31 rr. .l'. nr『N96/IⅡ/3(part) /\’ Physics′Γ opicaI Papcf

GCE A Level Physics 1976-2003

{t9 (,,t

(I)

E . r 1; l l r i nv v l r l t i s r ) t c i u t t b y t l r c r . c s i . r/ i l r l r . o l ' l r n r l l er i a i . f

l. i.

t l r cp o t c n t i acl l i i l c r . c n c c r r o s s c c l r g i l r e, aL th t l t eP o r v cs u P p l i c r l t h c L - n s i n c . to l t l r c l l - a c t i o n l ' t l i c p o v v c r t r p p l i c d, h i c hi s o s u r u s cb y t h c c n q i n c . d til

″ 丬 rc丿

S h r t r, r, t l r l t ltr c L l r r i i r r s, l 1 i 1: r - c s i s t i v i t ys n r c l t s u r c r l r t h i isO rrr. I3l N 9 7/ i l t/ . 1( p l r r )

il. (a)

70r‘J丿 (i) (ii)

Wfratis Incantl'tyan elt:r:trit: r'ttr.rattt? E x p l a i n r v h y p o w e r i s r c q u i r - e co r n u i n t a i ra n tl r c l c c t r i cc u l ' l ' e n n a r n e t a l l i c o r r d u c t o r .: it l4l A r n e t a o l ' r e s i s t i v i tp i s u s e ctlo r n a k e n c l c c t r i c l y a c a b l e o f c r o s s - s e c t i o n a lr e i iA . S h o r v t l r a t t h e r e s i s t a n c r . p c r u n i t l c n g t ho l, t l t c c u b l ci s g i v c n c l - r yh c c x p r c s s i o n l r'- pl iL

I S x p l a i n h c 1 ' o l k r w i n ga c t s a b o u t t l r e s i r p p l y t o r h e t f cngl c. n (i) A r a i l r v u y c r n p l o y e er v l r o t o u c h c s t l - r ct r . z i c k t l r l o u g hw h i c h t l r e r ci s i l c L l r r . c loIl ' l g 0 A d o e s t n o t g e ta n e l c c t r i c h o c k . s A h i g l r v o l r a g e u p p l yi s e . s s e n r i ab r a r a i l w a y s l l s y s t e l n u c l r st h i s . s a

(i)

(ii)

(ii)

S o r l e e l e c t r i c a la p p l i a n c e s r e u s e d r v i t h l o n g a cablcs[o connectthcrn Lo the clectricalsupply. Stateand cxplainlwo r-easons tireconnecting 72 (u) why cableshoLrld havea low valuelor i.. l.6l J9B/lll/2(part)

(iii) A dift'c'e't cLrrrent 'eecJecl is wlicrr thc train is clirnbirrg hill l'ronrthat l a when travclling a[ thesamespeed the ilat.. on 16] N98/III/4 Statewhat is nreant Lry (i) tltercsisturtce sanrple ol'a ol,a rnetal,

(ii) the resi'srivir'v tue of the tal' .lggrrrus tprl,ll(i) (ii) Explainwhatis nrcant itnelectriccurrent. by Explainivhy somesolidsareelectrical concluctors arrdsomeareinsulators. t3l

7l (u) Det'ine(i) (ii) potetttiul di.fJcranca, the valr.

73rrr丿

[2]

State tlre ecluation relatingtlte resi.stancc ol' a wirc R t o i t s a r e a o l ' c r o s s - s e c t i o/n i t s l c n g t h/ a n d t h e, r e s i s t i v i t y o f ' t h e n t a t c r i ao l ' i, v h i c ht .i s r n a r l e . p l i Ill The overhead wire u.sed sultplypowcr to tlic ctrginc to ol' a train has areaof cross-ser:tion x l0-s rn2anclis 5.00 nradeo1' copperof resistivit| .72 x I 0-8ern. Calculate y t h e r e s i s t a n co f o n e k i l o l n c

t r c c n g t h l ' t h cw i r e . c l o

( i i i ) D e s c r i b e l c c t r i c a l o r i d u c t i oin a n r e t a l . c n

Explain why it is dil'llcult to quote a value lbr the rcsistance a l'ilament of larnn, I〕【 In a gas, conductionoccurs as a result of negative p a r t i c l e sf l o r . v i n g n e w a y a n d p o s i t i v e p a r t i c l c s o l ' l o w i n g i n t h c o p p o s i t ec i i r e c t i o n, s i i l u s t r a t e c i n a l I r i g .1 2 . 74rfr丿冫、丿

l2)rf/丿 Itig. I I shon,s the arrangerncnt lbr supplyingpower

to nn crrgine.A 25 kV supply is used ancltlre retul.lt currenfll'onr tlre enginereturnsthroughthe track..t'hc lesistl'rrrcc l<ilonrctrc tlrc overhcadtvir-cis as pel of c: a l c u l a t cid ( r: ) a n d t l r c r e s i s t a n co l, t h c t r a c kc a n b e n e neglected.o v e r h e a dw i r e\— -¨

(;oppel' colrcltrctor coltcltrctor'

c丿

gasat lorv prcssrrrc Fig.12

corrcirictor

9

l200 50V

track

eng{ne

In this casc,(he copperconductors the gas carry a to currcntol'0.28 rnA. The nunrberof negativeparticles p a s s i n _a 1 y p o i n t i n t h c g a s p e r u n i t t i m e i s rn *-t x 1..5(> 111rs uncithc chargcorr cnchnegativeparticlc i s - l . 6 0x l 0 - r e . C Calc:ulate (i) (ii; tlrc rrcgative chargellov;ing l)a.st any point in the gasper scconcl, t l r c p o s i t i v e h a r g cl T o w i n g a s ta n y p o i n t i r r t h e c p ga.s sccotrcl, per

Fig" tl Colr.sicicr l'irsl.rvlren tlrc cnginc i.s close to thc powcr su1-r1tly recluircs and 6700 kW of' llowct.. Calculate currentwhich is neeclccl. tlre 21丨 (ii) When the engineis 30 krn fr.orn powcr suplrly, tlic it is supplied itha currcnt l' lg0 A. Calcrrlatc w o l. tlrc rcsistancc tlrc ovcrhcadwire betwecrr ol' t h c p o r v e r u p p l ya r r dt l r cc n g i n c, s

( i i i ) t h en u r l b c ro f p o s i t i v e l y h a r g c c l a r t i c l e s a s s i n g c p p arry point irr the gns per secorrcl, given tlriit thc c l r a r g e n c a c l r o s i t i v e a f t i c l c s+ 3 . 2 0x l 0 - r eC . o p p i[6] 'A' Physics Topical Paper

[7 CurrentElcctricity

194

17Cur

GCE A Level Physics 1976-2003

In c .

(d) 'r(r)

B y c o n s i d c r i n t h c s i g n i l i c l n tf i g u r c s v a i l a b l e,x p l a i n g a e w h y y o t r rr l t s w c r s o ( c ) ( i i )a n d( i i i ) r r c u n r e l i a b l e .1 2 ) t I n o n e p r a c t i c a c x i r m p l co f ' c l c c t r i c a c o n c J u c t i o n ' l l ol p a r t i c l e st h r o u g hl g a s, a m a g t r c t i cl c l d i s a p p l i c d l a c r o s s h e g a s .I n s t e a d f t r a v e l l i n g i r e c t l va l o n gt h e t o d t u b e t h e p o s i t i v ea n d n e g a t i v ec h a r g e s r a v e l l l o r r g t, c l i l 'c r e n tp n t h su ss h o w ni n F i g . 1 3 . f typical path ol' charges negative⊥ T

h i c hi s

tilto rhe tl'ack A cloes ailway

Fig. 1404mΛ

The averagc tlrickness the skin of his harrd is of I mrn.Estirnate curlentthroLrglt person. the tlre[2] ( i i i ) Discusstlvo

ltrctors,rel'erredIo:tbove, which aff'ectthe nragnitude tlre current and lrence of aflect the possibledanger. frorr electric shock. O n c o b v i o u s s a l ' c t yp r e c a u t i o n i s t o k e e p live wires well insulated. lrat other safety W precautions you suggest? do t4] N2000/ril/4

'-ainis,elling

t6l )8/IU/4

coppef corrrlttctor C

typical patlrof positive harges c Fig. 13

coPper cotrclttctor

(i)

t4l (part)

Statbthe directionof tlrc appliedrnagnetic field. yonr answer. Explainhow you obtained H o w i s i t p o s s i b l eo r t h e p o s i t i v e a r t i c l e s t i l l t o f p straight travelin an apparently line?

(ii)

uctorsra r

(iii) State Kirchlrofl"sflrst law and use it to l-indthc c u r r e n t n c o n d u c t oC . i r ( i v ) S u g g e s tw h a t i s h a p p e n i n gt o t h e p a r t i c l e sn t surlaccS of thc copperconductor C. i8l N99/ilr/5 7 4 ( r t ) S t a t e t l r e e q u a t i o nl i n k i n g c h a r g eQ, c u r r e n t/ a n d t i r n et . tl l (b) C a l c u l a t c h c c h a r g ew h i c l r l 1 o w sp l s t a n y p o i n t i n r t c i r c u i tw h e n a c u l ' r e n o f 6, 2 m A c x i s t si n t h c c: i r c u i t t you ltot give your itnswct' lbr one hour. Why slroulcl f to 4 signilicant igures? tZ) Dellnepotctttial rliffurettcc. tll

trl rr the

ttllative t i cl e s ted in

F丶

μ

ιιc t。

ˉ

c丿四

A wuterheatcris rnarked 230 V, 3000W. It is switchcd on for 5000 seconds. this heater, For calculate (i) the currentthroughthe heater, ol the resistance tlre heater,

fr/ el ticles re is rticle (e) n tlte 1 the

(ii)

(iii) tlreenergysupplied the hcater by durirrg this time.

tllThe resistivityof the hLrman body is low compared w i t l r t h e r c s i s t . i v i t vf s k i n .w h i c h i s a b o u t x l 0 a f l r n o 3 lbr dry skin. (i) Itror layerol'dry skin I rnm tltick,dctermine a tlrc resistitnce a I cm2 areaof skin. of t3l rvlrois well earthcd, A person, grabs accidentally l a w i r e o 1 ' d i a r n e t e r 4 c r n a t a p o t e n t i ao l ' 5 0 V . 0. H i s h a n d n r n k c s c o n t i l c t r . v i t ht l r e w h o l o o1'thewire over A distancc 9 cnr circurnf'erence of a ss h o w ni n F i g . 1 4 . ' A ' P l r y s i c s ' f o p i c a la P e r P

(ii);sirtg theI (',-\

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l7 CurrentElectricity

195

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