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narjmWu H moS >H mo Cma-nwpVH m Ho _wI-n>na Ad` {bIo &Candidates must write the Code on the

title page of the answer-book.

Series SSO H moS> Z.Code No.

amob Z.Roll No.

^m{VH {dkmZ (gmpVH )

PHYSICS (Theory)

{ZYm[aV g_` : 3KQ>o A{YH V_ AH : 70

Time allowed : 3 hours Maximum Marks : 70

H n`m OmM H a b| {H Bg Z-n _o _w{V n> 19h & Z-n _| Xm{hZohmW H s Amoa {XE JE H moS >Z~a H mo N>m Cma -nwpVH m Ho _wI-n> na

{bI| &

H n`m OmM H a b| {H Bg Z-n _| >

26

Z h & Hn`m Z H m Cma {bIZm ew H aZo go nhbo, Z H m H _mH Ad` {bI|& Bg Z-n H mo nT>Zo Ho {bE 15 {_ZQ >H m g_` {X`m J`m h & Z-n H m {dVaU nydm

_| 10.15~Oo{H m OmEJm & 10.15~Oogo 10.30 ~Oo VH N>m Ho db Z-n H mo nT>|JoAma Bg Ad{Y Ho XmamZ doCma-nwpVH m na H moB Cma Zht {bI|Jo&

Please check that this question paper contains 19printed pages.

Code number given on the right hand side of the question paper should bewritten on the title page of the answer-book by the candidate.

Please check that this question paper contains 26questions. Please write down the Serial Number of the question before

attempting it.

15 minute time has been allotted to read this question paper. The questionpaper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., thestudents will read the question paper only and will not write any answer onthe answer-book during this period.

55/3/G

SET-3

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gm_m` {ZX}e:

(i) g^rZ A{Zdm h& Bg Z-n _| Hw b 26Z h &

(ii) Bg Z-n Ho 5^mJ h : IS> A, IS> ~, IS> g, IS> X Ama IS> ` &

(iii) IS> A _| 5Z h, oH H m 1AH h & IS> ~ _| 5Z h, oH Ho 2 AH h&

IS> g _| 12Z h, oH Ho 3 AH h & IS> X _| 4 AH H m EH _y`mYm[aV Z

hAma IS> ` _| 3Z h, oH Ho 5AH h &

(iv) Z-n _| g_Jna H moB {dH n Zht h & VWm{n, Xmo AH m|dmbo EH Z _|, VrZ AH m|

dmbo EH Z _| Ama nmM AH m|dmboVrZm| Zm| _| AmV[aH M`Z XmZ {H m J`m h&

EogoZm| _| AmnH mo{XE JE M`Z _| go Ho db EH Z hr H aZm h &

(v) Ohm Amd`H hmo Amn {ZZ{b{IV ^m{VH {Z`VmH m|Ho _mZm| H m Cn`moJ H a gH Vo h :

c = 3 108m/s

h = 6.63 1034Js

e = 1.6 1019C

o= 4107T m A1

o= 8.854 1012C2 N1 m2

o4

1

= 9 109N m2C2

me= 9.1 1031kg

yQ>mZ H m `_mZ= 1.675 1027kg

moQ>mZ H m `_mZ= 1.673 1027kg

AmdmoJmmog`m= 6.023 1023{V Jm_ _mob

~moQ>O_mZ {Z`VmH = 1.38 1023JK1

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General Instructions :

(i) Allquestions are compulsory. There are26questions in all.

(ii) This question paper has five sections : Section A, Section B, Section C,Section D and Section E.

(iii) Section A contains five questions of one mark each, Section B containsfivequestions of twomarks each, Section C contains twelve questions of

three marks each, Section D contains one value based question of

fourmarks and Section E contains threequestions offivemarks each.

(iv) There is no overall choice. However, an internal choice has been providedin one question of two marks, one question of three marks and all the three

questions of five marks weightage. You have to attempt only one of the

choices in such questions.

(v) You may use the following values of physical constants wherevernecessary :

c = 3 108m/s

h = 6.63 1034Js

e = 1.6 1019C

o= 4107T m A1

o= 8.854 1012C2 N1 m2

o4

1

= 9 109N m2C2

me= 9.1 1031kg

Mass of neutron = 1.675 1027kg

Mass of proton = 1.673 1027kg

Avogadros number = 6.023 1023per gram mole

Boltzmann constant = 1.38 1023JK1

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IS> ASECTION A

1. `{X ~am~a _moQ>mB Ho H mna (Vm~o ) VWm _J{ZZ Ho Vmam| Ho {Vamo Y Amng _| ~am~a h, VmoBZ_| go {H g nXmW Ho Vma H s b~mB A{YH h ? AnZo Cma H s nw{> Ho {bE H maU{b{IE & 1Two wires, one of copper and the other of manganin, have sameresistance and equal thickness. Which wire is longer ? Justify youranswer.

2. {H gr E.gr. (a.c.) n[anW _|, Vmj{UH dmoQ>Vm VWm Ymam Ho H _e: _mZ h V = 200 sin 300 t dmoQ> Ama I = 8 cos 300 t Eopn`a & `m n[anW H s H{VYm[aVr` h `m oaH s` ?H maU Xr{OE & 1In an a.c. circuit, the instantaneous voltage and current are

V = 200 sin 300 t volt and I = 8 cos 300 t ampere respectively. Is thenature of the circuit capacitive or inductive ? Give reason.

3. `hm AmaoI _| EH YZm_H {~XAmdoe H s jo aoImE XemB JB h & Q VWm P {~XAm|Ho ~rM {H gr An G Um_H Amdoe H s pW{VO D OmAm| Ho AVa H m {M `m hmoJm ?AnZo Cma H s nwpQ> Ho {bE H maU {b{IE & 1

The figure shows the field lines of a positive point charge. What will bethe sign of the potential energy difference of a small negative charge

between the points Q and P ? Justify your answer.

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4. {H gr b|g Ho XmoZm| nR>m| H s dHVm {`mEg_mZ (~am~a) h & `{X EH nR> H mo {Kg H a

g_Vb H a {X`m OmE, Vmo b|g H s \ moH g Xar VWm j_Vm (nmda) {H g H ma n[ad{VV

hmoJr ? 1

The radii of curvature of both the surfaces of a lens are equal. If one of

the surfaces is made plane by grinding, how will the focal length andpower of the lens change ?

5. `mnH sH V gMma `dWm Ho XemE JE bmH AmaoI _| X VWm Y ~mgm| Ho Zm_

{b{IE : 1

Name the boxes X and Y shown in the block diagram of a generalizedcommunication system :

IS> ~

SECTION B

6. gjon _o nQ> H s{OE {H _mo~mBb Q>obr\ moZr _ogMma {H g H ma hmoVm h& 2

AWdm

CnJh go gMma _|, gMma H s {H g _yb Umbr ({d{Y) H m Cn`moJ hmoVm h ? Bg {d{Y _|{H g H ma Ho VaJ gMaU H m Cn`moJ hmoVm h ? h1VWm h2DMmB`m| Ho Xmo EoQ>oZmAm|Ho~rM A{YH V_ pQ>aoIr` Xyar dHo {bE OH {b{IE & 2

Explain briefly how communication takes place using mobile telephony.

OR

Which basic mode of communication is used in satellite communication ?

Which type of wave propagation is used in this mode ? Write the

expression for the maximum line of sight distance d between twoantennas having heights h1and h2.

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7. (a) {ZZm{H V Zm{^H s` A{^{H m _| ZVWm AH m _mZ {ZYm[aV H s{OE :

n3XBaUn A

36

144

Z

235

92

(b) `{X oH Zm{^H s` A{^{H m _o moQ>mZ VWm yQ>mZm| XmoZm| H s g`m ga{jV

ahVr h, Vmo `_mZ {H g H ma D Om_| nmV[aV hmoVm h ?nQ> H s{OE & 2

(a) In the following nuclear reaction

n3XBaUn A

36

144

Z

235

92 ,

assign the values of Z and A.

(b) If both the number of protons and the number of neutrons areconserved in each nuclear reaction, in what way is the massconverted into energy ? Explain.

8. gmo{S>`_ Ho noQ>_r CgOZ aoIm Ho H me H s VaJX H m _mZ 589 nm h & Cg

BboQ>mZ H s J{VO D Om kmV H s{OE {OgHo {bE Xo ~mbr VaJX H m _mZ ^r BVZm hr

hmoJm & 2The wavelength of light from the spectral emission line of sodium is

589 nm. Find the kinetic energy of the electron for which it would have

the same de Broglie wavelength.

9. EH nXo H mo {H gr dVw go 90 cm Xar na aIm J`m h & EH Cmb b|g H s Xmo {^

pW{V`m|, {OZHo ~rM H s Xar 20 cm h, go nXo na dVw Ho Xmo {^ {V{~~ ~ZVo h &

b|g H s \ moH g Xar kmV H s{OE & 2

A screen is placed 90 cm away from an object. The image of the object on

the screen is formed by a convex lens at two different locations separated

by 20 cm. Determine the focal length of the lens.

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10. R {VamoY Ho I Ymamdmhr EH MmbH _| e{ j`nX H mo n[a^m{fV H s{OE & `h e{j` {H g n _| H Q> hmoVm h ? XemBE {H {dwV e{ Q>oeZ go Kam| VH {dwV Ymam bo

OmZodmbo Vmam| (gMaU Ho ~bm|) _| e{ j` H mo yZV_ H aZo Ho {bE `h Amd`H h {H

BZ Vmam| _| {dwVYmam Hs dmoQ>Vm H mo A{V C aIm OmE & 2

Define the term power loss in a conductor of resistance R carrying acurrent I. In what form does this power loss appear ? Show that to

minimise the power loss in the transmission cables connecting the power

stations to homes, it is necessary to have the connecting wires carrying

current at enormous high values of voltage.

IS> g

SECTION C

11. J Ho {-{Par `moJ Ho `{VH aU nQ>Z _| o{jV bjUm| VWm H bmg~ XrV EH b

{Par mam Cn {ddVZ nQ>Z Ho VrZ {d oXZH mar bjUm| H s VwbZm H s{OE Ama CZH s

`mIm H s{OE & 3

Compare and explain three distinguishing features observed in Youngs

double slit interference pattern with those seen for a coherentlyilluminated single slit producing diffraction pattern.

12. hmBS>moOZ na_mUw Ho~moa Ho A{^JhrVm| Ho Cn`moJ go, ndt (nth) H jm _| MH a bJmVo hE{H gr BboQ>mZ H s J{VO D Om (K.E.) Ho {bE OH wn H s{OE Ama XemBE {H

,r8

e.E.K

no

2

Ohm rn , ndt H jm H s {`m h & ndt H jm _| pW{VO D OmH m

H jr` {`m rngo `m g~Y h? 3

Use Bohrs postulates of hydrogen atom to deduce the expression for the

kinetic energy (K.E.) of the electron revolving in the nthorbit and show

that ,r8

e.E.K

no

2

where rnis the radius of the nthorbit. How is the

potential energy in the nthorbit related to the orbital radius rn?

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13. AND JoQ> (ma) VWm NOT JoQ> (ma) H s g`_mZ gma{U`m|Ho Cn`moJ mam XemBE {HNAND JoQ>, AND JoQ> VWm NOT JoQ H m (Bgr H_ _|) g`moOZ h & Bggo NAND JoQ>H s g`_mZ gmaUr ~ZmBE &

NANDJoQm| (mam|) H mo gmd{H JoQ> `m| H hm OmVm h ? 3

Using truth tables of AND gate and NOT gate show that NAND gate isan AND gate followed by a NOT gate. Hence write the truth table ofNAND gate.

Why are NAND gates called Universal Gates ?

14. Am`m_ _mSw>{bV (AM) VaJ Ho Cn hmoZo H mo nQ> H aZo Ho {bE {H gr gab _mSw>bH H mEH bmH AmaoI ~ZmBE & `m _mSw>{bV gHo Vm|H m Bgr n _| gmaU {H m Om gH Vm

h ?nQ> H s{OE & 3

Draw a block diagram of a simple modulator to explain how the AM waveis produced. Can the modulated signal be transmitted as such ?Explain.

15. `hm XemE JE n[anW AmaoI _| 10 FHo Mma g Ym[am| H mo 500 VH s gbmB go OmoS>mJ`m h & {ZYm[aV H s{OE : 3

(a) ZoQ>dH (OmbH _) H s Vw` Ym[aVm VWm(b) oH gYm[a na Amdoe &

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A network of four 10 F capacitors is connected to a 500 V supply asshown in the figure. Determine the

(a) equivalent capacitance of the network and

(b) charge on each capacitor.

16. 16 {VamoY Ho EH Vma H mo_moS>H a EH dJ ~Zm`m J`m h & BgH s EH wOm Ho Xmo{gam| go 9 V{dwV-dmhH ~b (B.E_.E\ .) Ho EH moV H mo{M AZwgma OmoS> {X`m J`mh& moV go br JB Ymam H m _mZ n[aH {bV H s{OE & Bg dJ Ho {gam| C VWm D Ho ~rM{d^dmVa kmV H s{OE &`{X Bg Vma H mo ItM H a XJwZr b~mBd EH g_mZ _moQ>mB H m EH Vma ~Zm {X`m OmEAma Cgr gob H mo Cgr H ma ~ZmE JE dJ H s EH wOm Ho {gam| Ho ~rM OmoS> {X`m OmE,VmoA~ BgHo {H gr {dH U Ho Xmo {gam| Ho ~rM {d^dmVa `m hmoJm ? 3

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A 16 resistance wire is bent to form a square. A source of emf 9 V is

connected across one of its sides as shown. Calculate the current drawn

from the source. Find the potential difference between the ends C and D.

If now the wire is stretched uniformly to double the length and once

again the same cell is connected in the same way, across one side of the

square formed, what will now be the potential difference across one of itsdiagonals ?

17. {H gr H moR> (M~a) _|65 104 TH m EH g_mZ Mw~H s` jo {d_mZ h & Bg jo _|EH BboQ>mZ jo go b~dV {Xem _| 48 106 m/s H s Mmb go doe H aVm h & nQ>

H s{OE {H Bg BboQ>mZ H m nW dmmH ma `m| h &dmmH ma H jm _| BgHo KyUZ H s Amd{mkmV H s{OE & `mAmd{m BboQ>mZ H s Mmb na {Z a H aVr h ?nQ> H s{OE & 3

A uniform magnetic field of 65 104T is maintained in a chamber. An

electron enters into the field with a speed of 48 106m/s normal to the

field. Explain why the path of the electron is a circle. Determine its

frequency of revolution in the circular orbit. Does the frequency depend

on the speed of the electron ? Explain.

18. Amd`H n[anW AmaoI ~ZmH a {H gr gma-gob na H me Ho AmnVZ go hmoZodmbr CZ VrZ_yb {H mAm|H m gjon _| dUZ H s{OE {OZgo {dwV-dmhH ~b (B.E_.E\ .) Cn hmoVmh& {H gr gma-gob Ho {bE I V A{^bmj{UH dH~ZmBE &

gma-gobm| Ho g{daMZ (~ZmZo) Ho {bE nXmW H m M`Z H aZo Ho {bE Amd`H Xmo_hdnym _mnXS>m| H m CboI H s{OE & 3

AWdm

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gjon _| dUZ H s{OE {H H me CgOH S>m`moS> (LED) H moH go ~Zm`m OmVm h AmaBgH s H m {d{Y H s `m`m H s{OE & nanamJV VmnXrV {dwV ~~m| H s VwbZm _|Eb.B.S>r. (LED)Ho VrZ _w` bm^ {b{IE & 3

Describe briefly using the necessary circuit diagram, the three basic

processes which take place to generate the emf in a solar cell when lightfalls on it. Draw the I V characteristics of a solar cell.

Write two important criteria required for the selection of a material for

solar cell fabrication.

OR

Describe briefly how light emitting diode is fabricated and explain its

working. Write three important advantages of LEDs over conventionalincandescent lamps.

19. YmVw H s EH N>S> H s b~mB l h& BgH m EH {gam YmVw Ho {H gr N>bo (db`) Ho Ho

na qhO {H m J`m hAma Xgam {gam N>bo H s n[a{Y na {Q>H m h& N>S> H mo v Amd{m go

Kw_m`m OmVm h& BgH s KyUZ Aj N>bo Ho g_Vb Ho b~dVh VWm N>bo Ho Ho go

hmoH a JwOaVr h & Bg KyUZ Aj Ho g_mVa EH pWa VWm EH g_mZ Mw~H s` jo B,gd {d_mZ h &

(a) Ho VWm N>bo Ho ~rM o[aV {dwV-dmhH ~b (B.E_.E\ .) Ho {bE OHmV H s{OE &

(b) `{X {X`m J`m h {H N>S> H m {VamoY Rh, Vmo Cn e{ H m _mZ `m hmoJm ? 3

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A metallic rod of length l is rotated with a frequency v, with one end

hinged at the centre and the other end at the circumference of a circular

metallic ring, about an axis passing through the centre and

perpendicular to the plane of the ring. A constant and uniform magnetic

field B parallel to the axis is present everywhere.

(a) Obtain the expression for the emf induced between the centre and

the ring.

(b) Given that the rod has resistance R, then how much power will be

generated ?

20. Eopn`a Ho `mnH sH V n[anWr` {Z`_ Ho {bE OH {b{IE & Cn w CXmhaU H sghm`Vm gog_`-Am{lV nX Ho _hd H mo nQ> H s{OE & 3

Write the expression for the generalized Amperes circuital law. Through

a suitable example, explain the significance of time-dependent term.

21. (a) {H gr boOa mam 6 1014 Hz Amd{m H m EH dUu H me Cn hmoVm h &

Cg{OV e{ H m _mZ 20 103 W h & Bg moV mam AmgVZ {H VZo \ moQ>mZ

{V goH S> Cg{OV {H E OmVo h ?

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(b) `hmAmaoI _|, Xmo YmVwAm| X VWm Y Ho {bE Amn{VV {d{H aUm| H s Amd{m (v)HogmW {ZamoYr {d^d V0 Ho {dMbZ (n[adVZ) H mo Xem`m J`m h & `{X XmoZm|YmVwAm| na Amn{VV {d{H aUm| H s VaJX g_mZ hmo, Vmo {H g YmVw go, (Xgar YmVwH s VwbZm _|) A{YH J{VO D Om Ho BboQ>mZm| H m CgOZ hmoJm ?nQ> H s{OE & 3

(a) Monochromatic light of frequency 6 1014 Hz is produced by alaser. The power emitted is 20 103W. How many photons persecond on an average are emitted by the source ?

(b) Figure shows variation of stopping potential (V0) vs. frequency (v)of incident radiation for two metals X and Y. Which metal willemit electrons of larger kinetic energy for same wavelength ofincident radiation ? Explain.

22. (a) _mZ br{OE {H {H gr Vmao go 6000 VaJX H m H me Am ahm h & Cg XaXeu

H s {d oXZ gr_m kmV H s{OE {OgHoA{^`H H m `mg 250 cmh &

(b) Xmo {P[a`m|(pbQ>m| ) Ho ~rM H s Xar (nmW`) 1 mm h VWm EH nXmBZgo 1 m

Xa aIm J`m h& oH {Par H s MmS>mB {H VZr hmoZr Mm{hE, Vm{H EH b {Par

nQ>Z Ho Ho r` C{R> Ho^rVa {-{Par nQ>Z Ho 10C{R> mV hmo gH| ? 3

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(a) Assume that the light of wavelength 6000 is coming from a star.

Find the limit of resolution of a telescope whose objective has a

diameter of 250 cm.

(b) Two slits are made 1 mm apart and the screen is placed 1 m away.

What should be the width of each slit to obtain 10 maxima of the

double slit pattern within the central maximum of the single slitpattern ?

IS> X

SECTION D

23. h[a AnZo Jmd Ho nmg pWV {H gr {dmb` _| 10dt (Xgdt) H jm H m N>m h & CgHoMmMmOr ZoCgo S>m`Zo_mo - w EH gmB{H b Cnhma _| Xr & dh `h OmZH a amo_m{MV hmo J`m{H A~ dh amV _| gmB{H b MbmVo hE ~~ Obm H a gS>H na nS>r dVwAm| H mo nQ>XoI gH Vm h & {H Vw, Cgo `h kmV Zht Wm {H `h S>m`Zo_mo H go H m H aVm h & CgZo `hZ AnZo{ejH go nyN>m & {ejH Zo h[a Ho Bg Z H mo S>m`Zo_mo H s H m {d{Y H mo nyarH jm H mo g_PmZo H m EH Adga _mZm &

{ZZ{b{IV Zm|Ho Cma Xr{OE : 4(a) S>m`Zo_mo Ho {gmV VWm CgH s H m {d{Y H m CoI H s{OE &

(b) h[a VWm CgHo {dkmZ {ejH mam X{eV Xmo-Xmo _y`m| H m CboI H s{OE &

Hari is a student of Class X in a school near his village. His uncle gifted

him a bicycle with a dynamo fitted in it. He was thrilled to find that

while cycling during night, he could light the bulb and see the objects on

the road clearly. He, however, did not know how this device works. Heasked this question to his teacher. The teacher considered it an

opportunity and explained the working of a dynamo to the whole class.

Answer the following questions :

(a) State the principle and working of a dynamo.

(b) Write two values each displayed by Hari and his Science teacher.

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IS> `

SECTION E

24. (a) {dwV bgnX H s n[a^mfm Xr{OE & BgH m Eg.AmB. (S.I.)_mH {b{IE &

(b) {H gr {dwV-jo Ho Ad`d {XE JE h : Ex= x, Ey= 0 VWmEz= 0, Ohm

EH {d_r` pWamH h & `hmXemE JE AmaoI _| KZ ( y~) H s wOm a h &

BgHo oH Vb go JwOaZo dmbo bg H m VWm BgHo ^rVa ^mdr Amdoe H m

n[aH bZ H s{OE & 5

AWdm

(a) g_{d^d nR> H s n[a^mfm Xr{OE & g_{d^d nR> Ho {H gr {~X na {dwV-jo

H s {Xem Cg {~X na nR> Ho A{^b~dV `m|hmoVr h ?

(b) {H gr {dwV{Ywd Ho H maU g_{d^d nR>m| H mo XemBE & Amdoem| go Xar Ho ~T>Zo

go Cmamoma g_{d^d n> Xa-Xa `m| hmo OmVo h ?

(c) Bg {Ywd Ho {bE, x Ho gmW {d^d V Ho n[adVZ H mo XemZo Ho {bE EH Jm\

(AmboI) ~ZmBE, Ohm x (x >> 2a), Xmo Amdoem| H mo Omo S>Zo dmbr aoIm Ho

AZw{Xe, {~X Amdoe qgo Xar h & 5

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(a) Define the term electric flux. Write its S.I. unit.

(b) Given the components of an electric field as Ex = x, Ey = 0 and

Ez = 0, where is a dimensional constant. Calculate the flux

through each face of the cube of side a, as shown in the figure, and

the effective charge inside the cube.

OR

(a) Define equipotential surface. Why is the electric field at any point

on the equipotential surface directed normal to the surface ?

(b) Draw the equipotential surfaces for an electric dipole. Why does

the separation between successive equipotential surfaces get wider

as the distance from the charges increases ?

(c) For this dipole, draw a plot showing the variation of potential V

versus x, where x (x >> 2a), is the distance from the point charge

q along the line joining the two charges.

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25. (a) Q>mg\ m_a H s H m {d{Y Ho {gmV H mo {b{IE & Cn w AmaoIm| H s ghm`Vm go

XemBE {H {H gr Cm`r Q>mg\ m_a _o Vma {H g H ma bnoQ>o OmVo h &

(b) {H gr AmXe Q>mg\ m_a Ho {bE, CgH s mW{_H VWm {Vr`H HwS>{b`m| _| \o am|

H s g`m HonXm| _|, (i){ZJV VWm {Zdoer dmoQ>VmAm| Ama (ii) {ZJV VWm {Zdoer

YmamAm|Ho ~rM AZwnmV Ho {bE OH wn H s{OE &

(c) dmV{dH Q>mg\ m_am| _| D Om j` Ho _w` moV `m h VWmBZH mo H _ Hgo {H m

OmVm h ? 5

AWdm

(a) Mb Hw S>br Ymam_mnr (JdoZmo_rQ>a) H m EH Zm_m{H V AmaoI ~ZmBE & BgHo H m

H aZoH m {gmV {b{IE & Bg_| w Z_ bmoho Ho H moS> H m `m H m h ?

(b) (i) Ymam gwJm{hVm VWm (ii)dmoQ>Vm gwJm{hVm nXm| H s n[a^mfm Xr{OE &

(c) {H gr JdoZmo_rQ>a H mo (i) dmoQ>_rQ>a _| VWm (ii) Eo_rQ>a _| nmV[aV H aZo Ho {bE

w {gmV H mo nQ> H s{OE & 5

(a) Write the principle of working of a transformer. Show, with the

help of suitable diagrams, how the windings of a step-up

transformer are done.

(b) Assuming the transformer to be an ideal one, deduce the

expression for the ratio of (i) output voltage to input voltage and(ii) output current to input current in terms of the number of turns

in the primary and secondary coils.

(c) What are the main sources of energy loss in actual transformers

and how are these reduced ?

OR

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55/3/G 18

(a) Draw a labelled diagram of a moving coil galvanometer. State its

working principle. What is the function of a cylindrical soft iron

core used in it ?

(b) Define the terms (i) current sensitivity and (ii) voltage sensitivity.

(c) Explain the underlying principle used in converting agalvanometer into a (i) voltmeter and (ii) ammeter.

26. (a) nyU AmV[aH namdVZ H s n[aKQ>Zm Ho g^d hmoZo Ho {bE Amd`H eVmo

({V~Ym|) H m CboI H s{OE &

(b) EH {H aU AmaoI H s ghm`Vm go XemBE {H H mCZ H mM Ho g_H moUr` g_{~mh{_ H m Cn`moJ CQ>m {V{~~ mV H aZo _|{H g nH ma hmoVm h &

(c) Amd`H AmaoI H s ghm`Vm go gjon _| nQ> H s{OE {H nyU AmV[aH namdVZ

H s n[aKQ>Zm H m Cn`moJ H m{eH VVwAm| _| Hgo hmoVm h & EH CXmhaU H s

ghm`Vm go g_PmBE {H H m{eH VVwAm| H m Cn`moJ H m{eH gHoVm| Ho gmaU

(gMaU) _| Hgo hmo gH Vm h & 5

AWdm

(a) `{X t = 0 na {H gr VaJmJH m AmH ma {X`m J`m hmo, Vmo `h XemZo Ho {bE Cn w

AmaoI ~ZmBE {H t = t1na VaJmJ Ho AmH ma H mohmBJog H s `m{_Vr` gaMZm

H s ghm`Vm go mV {H m Om gH Vm h&

(b) {H gr g_Vb VaJmJ Ho {dab _m`_ go gKZ _m`_ _| doe (gMaU) na {dMma

H aVohE Zb Ho AndVZ {Z`_ H m g`mnZ H s{OE & XemBE {H {H gr VaJ Ho

gKZ _m`_ _| AndVZ go CgH s VaJX VWm gMaU Mmb KQ>Vr h, {H Vw

CgH s Amd{m dhr ahVr h & 5

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(a) State the essential conditions for the phenomenon of total internal

reflection to take place.

(b) Draw a ray diagram to show how a right isosceles prism made of

crown glass can be used to obtain the inverted image.

(c) Explain briefly with the help of a necessary diagram, how the

phenomenon of total internal reflection is used in optical fibres.

Illustrate giving an example how optical fibres can be employed for

transmission of optical signals.

OR

(a) Draw a suitable diagram to demonstrate that given the shape of a

wavefront at t = 0, its shape at a later time t1 can be obtained

using Huygensgeometrical construction.

(b) Consider the propagation of a plane wavefront from a rarer to a

denser medium and verify Snells law of refraction. Show that

when a wave gets refracted into a denser medium, the wavelength

and speed of propagation decreases but the frequency remains the

same.