1203board Set E

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Sample Paper 2012

Class XII

Subject PHYSICS

Time: 3 Hours (Theory) Max Marks:

70

Geera! "structios

(a) All questions are compulsory.

(b) Questions 1 to 8 carry one mark each, questions 9 to 18 carry two marks each,

questions 19

to 27 carry three marks each an questions 28 to !" carry #$e marks each.

#hysica! costats:

% & ! ' 1"8ms h & . ' 1"*!+s e & 1. ' 1"*19 % A$o-aros number /A & ."2! ' 1"2!

mole 0ass o neutron mn & 1. ' 1"*27 k- 0ass o electron me & 9 ' 1"*!1 k-

1. A (hypothetical) bar ma-net (A) is cut into two equal parts. 3ne part is now kept o$er

the other, so that pole %2 is abo$e %1. 4 0 is the ma-netic moment o the ori-inal

ma-net, what woul be the ma-netic moment o the combination so orme51

2. /ame the quantity represents minimum ma-netic moment o a re$ol$in- electron.6rite its e'pression

1

!. A rectan-ular wire rame, shown below, is place in a uniorm ma-netic #el irecte

upwar an normal to the plane o the paper. he part A is connecte to a sprin-. he

sprin- is stretche an release when the wire A has come to the position A (t&").

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ow woul the inuce em $ary with time5 /e-lect ampin-

1

+. /ame the characteristics o electroma-netic wa$es that (i) increases (ii) remains

constant in the electroma-netic spectrum as one mo$es rom raiowa$e re-ion

towars ultra$iolet re-ion. 1

:. A partially plane polari;e beam o li-ht is passe throu-h a erence in their

electrical conucti$ities5 1

8. ?our nuclei o an element use to-ether to orm a hea$ier nucleus. 4 the process is

accompanie by release o ener-y, which o the two * the parent or the au-hter

nucleus woul ha$e a hi-her binin- ener-ynucleon5

1

9. @eepin- the $olta-e o the the char-in- source constant, what woul be the percenta-e

chan-e in the ener-y store in a parallel plate capacitor i the separation between its

plates were to be ecrease by 1"5

2

1".wo cells o em B1 an B2 ha$e internal resistance r1 an r2. Ceuce an e'pression or

equi$alent em o their parallel combination.

$% &

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A cell o em (B) an internal resistance (r) is connecte across a $ariable e'ternal

resistance (D).

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1:. Ki-ht o wa$elen-th ::" nm. is incient as parallel beam on a slit o with ".1mm. ?in

the an-ular with an the linear with o the principal ma'ima in the resultin-

i>raction pattern on a screen kept at a istance o 1.1m rom the slit. 6hich o thesewiths woul not chan-e i the screen were mo$e to a istance o 2.2m rom the slit5

2

1. ow the etection o Amplitue moulate wa$e is one. 6hat is the unction o

recti#er in etection5

2

17. 6hen a char-e particle enters the ma-netic #el with some $elocity

(a) 6hat will be the irection an ma-nitue o orce on char-e particle

(b) 4n which two cases their will be no orce on the char-e particle

2

18. An armature coil consists o 2" turns o wire, each o area A & "."9m2an total

resistance1:.4t rotates in a ma-netic #el o ".: at a constant requency o 1:"

;. %alculate the $alue o (i) ma'imum (ii) a$era-e inuce em prouce in the coil

2

19. Blectroma-netic raiations with wa$elen-th (i) 1are use to kill -erms in water

puri#ers. (ii) 2are use in E communication systems (iii) !plays an important role in

maintainin- the earths warmth. /ame the part o electroma-netic spectrum to whichthese raiations belon-. Arran-e these wa$elen-ths in ecreasin- orer o their

ma-nitue ecreasin- orer o their ma-nitue. !

2".wo capacitors with capacity %1 an %2 are char-e to potential E1 an E2 respecti$ely

an then connecte in parallel. %alculate the common potential across the

combination, the char-e on each capacitor, the electrostatic ener-y store in the

system an the chan-e in the electrostatic ener-y rom its initial $alue.

!

3D

Ceuce an e'pression or electric potential ue to an electric ipole at any point on its

a'is. 0ention one contrastin- eature o electric potential o a ipole at a point as

compare to that ue to a sin-le char-e.

21. Craw the input an output characteristics o a transistor in its common emitter

con#-uration. B'plain brieLy the meanin- o the term Macti$e re-ion in these

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characteristics. ?or what practical use, o we use the transistor in this Macti$e re-ion5

!

22. 6hat is satellite wa$e propa-ation5 6hich two communication methos make use o

this moe o propa-ation5 4 the sum o the hei-hts o transmittin- an recei$in-

antennae in line o si-ht o communication is #'e at h, show that the ran-e is

ma'imum when the two antennae ha$e a hei-ht h2 each.

!

2!. B'plain the ori-in o spectral lines o hyro-en usin- ohrs theory. 0ark transisitions

corresponin- Kyman an almer series he wa$elen-th o the secon line o the

balmer series in the hyro-en spectrum is +81 Ao .%alculate the wa$elen-th o the

#rst line. !

2+. 6hen a circuit element MH is connecte across an a.c. source, a current o A Lows

throu-h it an this current is in phase with the applie $olta-e. 6hen another element

MF is connecte across the same a.c. source, the same current Lows in the circuit but it

leas the $olta-e by 2 raians. (i) /ame the circuit elements H an F.(ii) ?in the

current that Lows in the circuit when the series combination o H an F is connecte

across the same a.c.$olta-e.(iii)

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27.he -i$en -raphs show the $ariation o the stoppin- potential Es with the requency ()o the incient raiations or two i>erent photosensiti$e materials 01 an 02.(i) 6hat

are the $alues o work unctions or 01 an 025 (ii) he $alues o the stoppin- potential

or 01 an 02 or a requency ! (O"2) o the incient raiations are E1 an E2

respecti$ely. =how that the slope o the lines equals

!

28.wo circular coils H an F ha$in- raii D an D 2 respecti$ely are place in hori;ontal

plane with their centers coinciin- with each other. %oil H has a current 4 Lowin-

throu-h it in the clockwise sense. 6hat must be the current in coil F to make the total

ma-netic #el at the common centre o the two coils, ;ero5 6ith the same currents

Lowin- in the two coils, i the coil F is now lite $ertically upwars throu-h a istance

D, what woul be the net ma-netic #el at the centre o coil F5

3D :

=tate iot*=a$arts Kaw. Isin- this law, eri$e the e'pression or the ma-netic #el ue to

current carryin- circular loop o raius D, at a point, which is at a istance H rom its

center alon- the a'is o loop.%onsier two parallel co*a'ial circular coils o same raius Dan number o turns /, carryin- same current 4 in same irection, separate by a istance

D =how that the #el on the a'is aroun the mi*point between the coils in uniorm o$er a

istance that is small as compare to D is -i$en by

& (".72"/4) D

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29. (i) Isin- the relation or reraction at a sin-le spherical reractin- surace, eri$e the

lens makers ormula.(ii) %alculate the istance , so that a real ima-e o an obNect at

3, 1:cm in ront o a con$e' lens o ocal len-th1"cm be orme at the same point 3.he raius o cur$ature o the mirror is 2"cm. 6ill the ima-e be in$erte or erect5

3D :

B'plain how the polari;ation takes place5 6rite two uses o polarois5

Ki-ht rom an orinary source (say a soium lamp) is passe throu-h a

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6hen a resistance o 1:is connecte in series with MF, the null point is oun to shit by

1"cm towars the en A o the wire. ?in the position o null point i a resistance o !

were connecte in parallel with MF.

Shailendra Rawat

Director Academics: VECTOR CLASSES

[email protected]

Phone No. !"#$%$&&

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1203board Set E

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