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CBSE Class 12 Board Exam 2017 : Physics

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SET-1 H$moS> Z . Series GBM Code No. amob Z . 55/1 narjmWu H$moS >H$mo C ma-nwp VH$m Ho$ _wI-n >na Ad ` {bIo & Roll No. Candidates must write the Code on the title page of the answer-book. H $n`m Om M H$a b| {H$ Bg Z-n _o _w{ V n > 16 h & Z-n _| Xm{hZo hmW H$s Amoa {XE JE H$moS >Z ~a H$mo N>m C ma -nwp VH$m Ho$ _wI-n > na {bI| & H $n`m Om M H$a b| {H$ Bg Z-n _| >26 Z h & H $n`m Z H$m C ma {bIZm ew $ H$aZo go nhbo, Z H$m H $_m H$ Ad ` {bI| & Bg Z-n H$mo n T>Zo Ho$ {bE 15 {_ZQ >H$m g_` {X`m J`m h & Z-n H$m {dVaU nydm _| 10.15 ~Oo {H$`m OmEJm & 10.15 ~Oo go 10.30 ~Oo VH$ N>m Ho$db Z-n H$mo n T>|Jo Am a Bg Ad{Y Ho$ Xm amZ do C ma-nwp VH$m na H$moB C ma Zht {bI|Jo & Please check that this question paper contains 16 printed pages. Code number given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. Please check that this question paper contains 26 questions. Please write down the Serial Number of the question before attempting it. 15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period. ^m {VH$ {dkmZ (g mp VH$) PHYSICS (Theory) {ZYm [aV g_` : 3 K Q>o A{YH$V_ A H$ : 70 Time allowed : 3 hours 55/1 Maximum Marks : 70 1 P.T.O. gm_m ` {ZX}e : (i) g^r Z A{Zdm` h & Bg Z-n _| Hw$b 26 Z h & (ii) Bg Z-n Ho$ nm M ^mJ h : I S> A, I S> ~, I S> g, I S> X Am a I S> ` & (iii) I S> A _| nm M Z h , `oH$ H$m EH$ A H$ h & I S> ~ _| nm M Z h , `oH$ Ho$ Xmo A H$ h & I S> g _| ~mah Z h , `oH$ Ho$ VrZ A H$ h & I S> X _| Mma A H$ H$m EH$ _y `mYm[aV Z h Am a I S> ` _| VrZ Z h , `oH$ Ho$ nm M A H$ h & (iv) Z-n _| g_J na H$moB {dH$ n Zht h & VWm{n, Xmo A H$m| dmbo EH$ Z _|, VrZ A H$m| dmbo EH$ Z _| Am a nm M A H$m| dmbo VrZm| Zm| _| Am V[aH$ M`Z XmZ {H$`m J`m h & Eogo Zm| _| AmnH$mo {XE JE M`Z _| go Ho$db EH$ Z hr H$aZm h & (v) Ohm Amd `H$ hmo, Amn {Z Z{b{IV ^m {VH$ {Z`Vm H$m| Ho$ _mZm| H$m Cn`moJ H$a gH$Vo h : c = 3 108 m/s h = 6.63 10 34 Js e = 1.6 10 19 C 0 = 4 10 7 T m A 1 0 = 8.854 10 12 C2 N 1 m 2 1 = 9 109 N m2 C 2 4 0 Bbo Q >m Z H$m `_mZ = 9.1 10 31 kg `yQ >m Z H$m `_mZ = 1.675 10 27 kg moQ>m Z H$m `_mZ = 1.673 10 27 kg AmdmoJm mo g `m = 6.023 1023 {V J m_ _mob ~mo Q > O_mZ {Z`Vm H$ = 1.38 10 23 JK 1 55/1 2 General Instructions : (i) All questions are compulsory. There are 26 questions 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 contains five questions of two marks each, Section C contains twelve questions of three marks each, Section D contains one value based question of four marks and Section E contains three questions of five marks each. (iv) There is no overall choice. However, an internal choice has been provided in 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 wherever necessary : c = 3 108 m/s h = 6.63 10 34 Js e = 1.6 10 19 C 0 = 4 10 7 T m A 1 0 = 8.854 10 12 C2 N 1 m 2 1 = 9 109 N m2 C 2 4 0 Mass of electron = 9.1 10 31 kg Mass of neutron = 1.675 10 27 kg Mass of proton = 1.673 10 27 kg Avogadro s number = 6.023 1023 per gram mole Boltzmann constant = 1.38 10 23 JK 1 55/1 3 P.T.O. I S> A SECTION A 1. g_mZ b ~mB Am a g_mZ { `m Ho$ {ZH $mo_ Am a Vm ~o Ho$ Vma loUrH $_ _| g `mo{OV h & BZ_| go Ymam I dm{hV H$amB JB h & H$m Z-gm Vma A{YH$ V V hmoJm ? AnZo C ma H$s nwp Q> H$s{OE & 1 Nichrome and copper wires of same length and same radius are connected in series. Current I is passed through them. Which wire gets heated up more ? Justify your answer. 2. `m {d wV -Mw ~H$s` Va J| D$Om Am a g doJ dhZ H$aVr h ? 1 Do electromagnetic waves carry energy and momentum ? 3. `{X ~ JZr a J Ho$ Amn{VV H$me H$mo bmb H$me go {V Wm{nV H$a {X`m OmE, Vmo H$m M Ho$ { _ H$m `yZV_ {dMbZ H$moU {H$g H$ma n[ad{V V hmoJm ? H$maU Xr{OE & 1 How does the angle of minimum deviation of a glass prism vary, if the incident violet light is replaced by red light ? Give reason. 4. Cg n[aKQ>Zm H$m Zm_ {b{IE Omo {d wV -Mw ~H$s` {d{H$aUm| H$s dm Q>_ H ${V H$mo Xem Vr h & Name the phenomenon electromagnetic radiation. 5. which shows the quantum ZrMo d{U V n[ap W{V _| g Ym[a H$s Y wdUVm H$m AZw_mZ bJmBE nature : Predict the polarity of the capacitor in the situation described below : 55/1 4 1 of 1 I S> ~ SECTION B 6. EH$b {Par {ddV Z Am a { {Par `{VH$aU Ho$ {bE Vrd Vm n Q>Z It{ME & AV Bg H$ma `{VH$aU Am a {ddV Z n Q>Zm] Ho$ ~rM Xmo A Vam| H$m C boI H$s{OE & 2 AWdm AY w{dV H$me {H$gr nmoboam BS> P1 go Jw OaVm h & O~ `h Y w{dV H$me nw O {H$gr A ` nmoboam BS> P2 go Jw OaVm h VWm `{X P2 H$m nmg-Aj P1 Ho$ nmg-Aj go H$moU ~ZmVm h , V~ P2 go Jw OaZo dmbo Y w{dV H$me nw O Ho$ {bE ` OH$ {b{IE & O~ H$m _mZ 0 go 2 Ho$ ~rM {dMaU H$aVm h , Vmo Vrd Vm _| {dMaU H$mo Xem Zo Ho$ {bE J m \$ It{ME & 2 Draw the intensity pattern for single slit diffraction and double slit interference. Hence, state two differences between interference and diffraction patterns. OR Unpolarised light is passed through a polaroid P1. When this polarised beam passes through another polaroid P2 and if the pass axis of P2 makes angle with the pass axis of P1, then write the expression for the polarised beam passing through P2. Draw a plot showing the variation of intensity when varies from 0 to 2 . 7. CZ {d wV -Mw ~H$s` Va Jm| H$mo nhMm{ZE {OZHo$ Va JX ` Bg H$ma {dMaU H$aVo h (a) 10 12 m < < 10 8 m (b) 10 3 m < < 10 1 m 2 `oH$ H$m EH$ Cn`moJ {b{IE & Identify the electromagnetic waves whose wavelengths vary as (a) 10 12 m < < 10 8 m (b) 10 3 m < < 10 1 m Write one use for each. 55/1 5 P.T.O. 8. Cg p W{V H$mo kmV H$s{OE {OZ_| {d wV Am a Mw ~H$s` jo g{Xem| H$s Cnp W{V _| {d{^ Mmbm| go J{V_mZ Amdo{eV H$Um| H$m Cn`moJ {H$gr {deof Mmb go J{V_mZ Amdo{eV H$Um| Ho$ M`Z Ho$ {bE {H$`m OmVm h & 2 Find the condition under which the charged particles moving with different speeds in the presence of electric and magnetic field vectors can be used to select charged particles of a particular speed. 9. H$j Vmn na {H$gr J gr` hmBS >moOZ na_mUw H$mo C mo{OV H$aZo Ho$ {bE 12 5 eV Ho$ Bbo Q >m Z nw O H$m Cn`moJ {H$`m OmVm h & Va JX `m| Am a VXZw $nr C g{O V aoImAm| H$s loUr {ZYm [aV H$s{OE & 2 A 12 5 eV electron beam is used to excite a gaseous hydrogen atom at room temperature. Determine the wavelengths and the corresponding series of the lines emitted. 10. (a) Wm`r Mw ~H$, Am a (b) {d wV -Mw ~H$ ~ZmZo Ho$ {bE Cn`w $ nXmW Ho$ Xmo JwU {b{IE & 2 Write two properties of a material suitable for making (a) a permanent magnet, and (b) an electromagnet. I S> g SECTION C 11. (a) (b) (a) 55/1 {XE JE {VamoYH$ Ho$ {gam| na AZw `w $ {d^dm Va H$mo n[ad{V V H$aZo na {V goH$ S> C n D$ _m 9 JwZr hmo JB & AZw `w $ {d^dm Va _| {H$g JwUH$ mam n[adV Z {H$`m J`m ? Xem E JE AmaoI _|, {H$gr moV Ho$ Q>{_ Zbm| go EH$ Eo_rQ>a A Am a 4 H$m EH$ {VamoYH$ g `mo{OV {H$`m J`m h & moV H$m Am V[aH$ {VamoY 2 Am a {d wV -dmhH$ ~b (emf) 12 V h & dmo Q>_rQ>a Am a Eo_rQ>a Ho$ nmR> m H$ n[aH${bV H$s{OE & The potential difference applied across a given resistor is altered so that the heat produced per second increases by a factor of 9. By what factor does the applied potential difference change ? 6 3 (b) In the figure shown, an ammeter A and a resistor of 4 are connected to the terminals of the source. The emf of the source is 12 V having an internal resistance of 2 . Calculate the voltmeter and ammeter readings. 12. 13. 55/1 (a) Am`m_ _m Sw>bZ {H$g H$ma {H$`m OmVm h ? (b) {H$gr Am`m_ _m Sw>{bV Va J Ho$ Xmo nm d ~ S>m| H$s Amd { m`m H $_e: 640 kHz Am a 660 kHz h & dmhH$ Am a _m Sw>bH$ {g Zb H$s Amd { m`m kmV H$s{OE & Am`m_ _m Sw>bZ Ho$ {bE Amd `H$ ~ S> Mm S>mB `m h ? (a) How is amplitude modulation achieved ? (b) The frequencies of two side bands in an AM wave are 640 kHz and 660 kHz respectively. Find the frequencies of carrier and modulating signal. What is the bandwidth required for amplitude modulation ? (a) {Z Z{b{IV AmaoI _|, `m g {Y S>m`moS> AJ {X{eH$ ~m`{gV h AWdm n M{X{eH$ ~m`{gV ? (b) nyU Va J {X Q>H$mar H$m n[anW AmaoI It{ME Am a BgH$s {H $`m{d{Y H$m C boI H$s{OE & (a) In the following diagram, is the junction diode forward biased or reverse biased ? (b) Draw the circuit diagram of a full wave rectifier and state how it works. 7 3 3 P.T.O. 14. H$me H$s \$moQ>m Z H$ nZm H$m Cn`moJ H$aHo$ `h Xem BE {H$ AmB Q>mBZ H$m H$me-{d wV g_rH$aU {H$g H$ma Wm{nV {H$`m Om gH$Vm h & H$me-{d wV ^md Ho$ CZ Xmo bjUm| H$mo {b{IE {OZH$s `m `m Va J {g m V mam Zht H$s Om gH$Vr & 3 Using photon picture of light, show how Einstein s photoelectric equation can be established. Write two features of photoelectric effect which cannot be explained by wave theory. 15. (a) (b) 16. 589 nm Va JX ` H$m H$moB EH$dUu H$me dm`w go {H$gr Ob Ho$ n R> na Amn{VV hmoVm h & `{X Ob H$m = 1 33 h , Vmo namd{V V H$me H$s Va JX ` , Amd { m Am a Mmb kmV H$s{OE & 1 55 AndV Zm H$ Ho$ H$m M go H$moB C^`mo mb b|g ~Zm`m J`m h {OgHo$ XmoZm| \$bH$m| H$s dH $Vm { `m g_mZ h & `{X Bg b|g H$s \$moH$g X ar 20 cm h , Vmo Amd `H$ dH $Vm { `m kmV H$s{OE & (a) Monochromatic light of wavelength 589 nm is incident from air on a water surface. If for water is 1 33, find the wavelength, frequency and speed of the refracted light. (b) A double convex lens is made of a glass of refractive index 1 55, with both faces of the same radius of curvature. Find the radius of curvature required, if the focal length is 20 cm. Hw$ S>{b`m| Ho$ `wJb Ho$ ~rM A `mo ` oaH$ d H$s n[a^mfm {b{IE & EH$-X gao na {bnQ>r h B Xmo b ~r g_mj n[aZm{bH$mAm|, {OZH$s b ~mB`m g_mZ h , Ho$ A `mo ` oaH$ d Ho$ {bE ` OH$ `w n H$s{OE & AWdm {H$gr Hw$ S>br Ho$ d oaH$ d H$s n[a^mfm {b{IE & {H$gr {d wV -dmhH$ ~b go g `mo{OV oaH$ L _| g {MV D$Om Ho$ {bE ` OH$ m V H$s{OE & (emf) OR Define self-inductance of a coil. Obtain the expression for the energy stored in an inductor L connected across a source of emf. 8 3 Ho$ moV Define mutual inductance between a pair of coils. Derive an expression for the mutual inductance of two long coaxial solenoids of same length wound one over the other. 55/1 3 3 17. (a) (b) {H$gr _rQ>a goVw H$m H$m` H$mar {g m V {b{IE & {H$gr _rQ>a goVw _|, AmaoI _| Xem E AZwgma, {VamoY g VwbZ {~ X m V hmoVm h & R Am a S Ho$ gmW X ar l1 na {VamoY S Ho$ nm d _| {H$gr AkmV {VamoY X H$mo g `mo{OV H$aZo na A~ g VwbZ {~ X X ar l2 na m V hmoVm h & l1, l2 Am a S Ho$ nXm| _| X Ho$ {bE gy m V H$s{OE & (a) Write the principle of working of a metre bridge. (b) In a metre bridge, the balance point is found at a distance l1 with resistances R and S as shown in the figure. 3 An unknown resistance X is now connected in parallel to the resistance S and the balance point is found at a distance l2. Obtain a formula for X in terms of l1, l2 and S. 18. 55/1 {H$gr `mnH$sH $V g Mma `d Wm H$m bm H$ AmaoI It{ME & {Z Z{b{IV _| `oH$ Ho$ H$m` {b{IE : (a) o{f (b) M Zb (c) A{^J mhr 9 3 P.T.O. Draw a block diagram of a generalized communication system. Write the functions of each of the following : (a) Transmitter (b) Channel (c) Receiver 19. 55/1 (a) {H$gr Q >m { O Q>a Ho$ VrZ I S>m| Ho$ H$m` {b{IE & (b) AmaoI _| AND JoQ> Ho$ {bE Xmo {Zdoer Va J $n A Am a B Xem E JE h & {ZJ V Va J $n It{ME Am a Bg bm {OH$ JoQ> Ho$ {bE g `_mZ gmaUr {b{IE & (a) Write the functions of the three segments of a transistor. (b) The figure shows the input waveforms A and B for AND gate. Draw the output waveform and write the truth table for this logic gate. 10 3 20. (a) (b) 21. (D) maH$ j_Vm L1 3 8 L2 6 1 L3 10 1 Draw a ray diagram depicting the formation of the image by an astronomical telescope in normal adjustment. (b) You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope ? Give reason. (a) Lenses Power (D) Aperture (cm) L1 3 8 L2 6 1 L3 10 1 ~m`mo gmdQ> {Z`_ {b{IE Am a Bg {Z`_ H$mo g{Xe $n _| ` $ H$s{OE & { `m R H$s Xmo gd g_ d mmH$ma Hw$ S>{b`m P Am a Q, {OZgo H $_e: 1 A Am a 3 A YmamE dm{hV hmo ahr h , XY Am a YZ Vbm| _| EH$-X gao Ho$ b ~dV Am a g Ho$ r aIr h & BZ Hw$ S>{b`m| Ho$ Ho$ na ZoQ> Mw ~H$s` jo H$m n[a_mU Am a {Xem kmV H$s{OE & (a) State Biot Savart law and express this law in the vector form. (b) Two identical circular coils, P and Q each of radius R, carrying currents 1 A and 3 A respectively, are placed concentrically and perpendicular to each other lying in the XY and YZ planes. Find the magnitude and direction of the net magnetic field at the centre of the coils. 11 3 (cm) b|g (a) (b) 55/1 gm_m ` g_m`moOZ _| {H$gr IJmobr` Q>obr H$mon (X a~rZ) mam {V{~ ~ ~ZZm {M{ V H$aVo h E {H$aU AmaoI It{ME & AmnH$mo {Z Z{b{IV VrZ b|g {XE JE h & BZ_| go {H$Z Xmo b|gm| H$m Cn`moJ, {H$gr IJmobr` Q>obr H$mon (X a~rZ) H$s aMZm H$aZo _|, CgHo$ Zo{ H$m Am a A{^ `H$ Ho$ $n _| H$a|Jo ? H$maU Xr{OE & 3 P.T.O. 22. Xmo gd g_ g_m Va n{ >H$m g Ym[a A Am a B {H$gr V dmo Q> H$s ~ Q>ar go g `mo{OV h Am a p dM S ~ X h & p dM H$mo A~ Imob {X`m OmVm h Am a BZ g Ym[a m| H$s n{ >H$mAm| Ho$ [a $ WmZ Ho$ ~rM namd wVm H$ K H$m H$moB namd wV ^a {X`m OmVm h & BZ XmoZm| g Ym[a m| _| namd wV ^aZo go nyd Am a namd wV ^aZo Ho$ n MmV g {MV Hw$b p Wa-d wV D$Om H$m AZwnmV kmV H$s{OE & 3 Two identical parallel plate capacitors A and B are connected to a battery of V volts with the switch S closed. The switch is now opened and the free space between the plates of the capacitors is filled with a dielectric of dielectric constant K. Find the ratio of the total electrostatic energy stored in both capacitors before and after the introduction of the dielectric. I S> X SECTION D 23. 55/1 Amem H$s _mVmOr Zo MoZm}{~b _| h B X K Q>Zm Ho$ {df` _| EH$ boI g_mMma-n _| n T>m & dh Bg boI Ho$ {df` _| Hw$N> A{YH$ Zht g_P nm`t Am a Bg boI go g ~p YV Hw$N> Z Amem go nyN>o & CgZo Omo Hw$N> H$jm XII _| ^m {VH$s _| grIm Wm, Cgr Ho$ AmYma na AnZr _mVmOr Ho$ Zm| Ho$ C ma XoZo H$m `mg {H$`m & (a) MoZm}{~b _| Ohm X K Q>Zm h B dhm na `m {V R>m{nV Wm ? AmnHo$ {dMma go Bg X K Q>Zm H$m `m H$maU Wm ? (b) MoZm}{~b na {V R>mnZ _| D$Om _w $ hmoZo H$s {H $`m H$s `m `m H$s{OE & (c) AmnHo$ {dMma go Amem Am a CgH$s _mVmOr mam X{e V _y ` `m Wo ? 12 4 Asha s mother read an article in the newspaper about a disaster that took place at Chernobyl. She could not understand much from the article and asked a few questions from Asha regarding the article. Asha tried to answer her mother s questions based on what she learnt in Class XII Physics. (a) What was the installation at Chernobyl where the disaster took place ? What, according to you, was the cause of this disaster ? (b) Explain the process of release of energy in the installation at Chernobyl. (c) What, according to you, were the values displayed by Asha and her mother ? I S> ` SECTION E 24. (a) (b) (c) (a) (b) b ~mB 2a Ho$ {H$gr { Y wd Ho$ H$maU CgH$s Ajr` aoIm na { Y wd Ho$ Ho$ go r X ar na p WV {H$gr {~ X na {d wV -jo E Ho$ {bE ` OH$ `w n H$s{OE & r >> a Ho$ {bE E Am a r Ho$ ~rM J m \$ It{ME & `{X `h { Y wd {H$gr EH$g_mZ ~m {d wV -jo E0 _| p WV hmo, Vmo Bg { Y wd H$s Wm`r Am a A Wm`r gm ` H$s p W{V H$m AmaoIr` {Z $nU H$s{OE Am a XmoZm| hr H$aUm| _| Bg { Y wd na H$m` aV ~b-AmKyUm] Ho$ {bE ` OH$ {b{IE & AWdm JmCg _o` H$m Cn`moJ H$aHo$ n R>r` Amdoe KZ d H$s {H$gr EH$g_mZ Amdo{eV AZ V ~ S>r g_Vb nVbr erQ> Ho$ H$maU {d wV -jo kmV H$s{OE & {H$gr AZ V ~ S>r g_Vb nVbr erQ> H$m EH$g_mZ n R>r` Amdoe KZ d + h & {H$gr {~ X Amdoe q H$mo AZ V go Bg Amdo{eV g_Vb erQ> Ho$ g _wI X ar r na p WV {H$gr {~ X VH$ bmZo _| {H$E JE H$m` Ho$ {bE ` OH$ m V H$s{OE & (a) Derive an expression for the electric field E due to a dipole of length 2a at a point distant r from the centre of the dipole on the axial line. (b) Draw a graph of E versus r for r >> a. (c) If this dipole were kept in a uniform external electric field E0, diagrammatically represent the position of the dipole in stable and unstable equilibrium and write the expressions for the torque acting on the dipole in both the cases. 5 5 OR 55/1 13 P.T.O. 25. (a) Use Gauss s theorem to find the electric field due to a uniformly charged infinitely large plane thin sheet with surface charge density . (b) An infinitely large thin plane sheet has a uniform surface charge density + . Obtain the expression for the amount of work done in bringing a point charge q from infinity to a point, distant r, in front of the charged plane sheet. {H$gr `w{ $ X H$mo {H$gr ac moV V = V0 sin t go g `mo{OV {H$`m J`m h & {Z Z{b{IV J m \$ _| {XImE JE EH$ MH $ _| dmo Q>Vm, Ymam Am a e{ $ Ho$ {dMaU H$mo Xem `m J`m h : (a) (b) (c) (d) `w{ $ X H$mo nhMm{ZE & BZ dH $m| A, B Am a C _| H$m Z dmo Q>Vm, Ymam Am a Cn^w $ e{ $ H$mo n[anW _| {Z ${nV H$aVo h ? AnZo C ma H$s nwp Q> H$s{OE & ac moV H$s Amd { m Ho$ gmW BgH$s {V~mYm {H$g H$ma {dMaU H$aVr h ? J m \$ mam Xem BE & n[anW _| Ymam Am a H$s{OE & ac dmo Q>Vm go BgHo$ H$bm-g ~ Y Ho$ {bE ` OH$ m V 5 AWdm 55/1 (a) ac (b) nyd go np M_ H$s Amoa {d Vm[aV 10 m b ~r H$moB j {VO MmbH$ N> S>, 5 0 ms 1 H$s Mmb go, 0 3 10 4 Wb m 2 Ho$ n dr Ho$ Mw ~H$s` jo Ho$ j {VO KQ>H$ Ho$ g_H$moU na {Ja ahr h & Bg N> S> _| o[aV {d wV -dmhH$ ~b (emf) H$m Vm j{UH$ _mZ kmV H$s{OE & O{Z H$m Zm_m {H$V AmaoI It{ME & Mw ~H$s` jo B H$s Cnp W{V _| KyU Z H$aVr h B N \o$am| H$s {H$gr Hw$ S>br, {Og_| `oH$ H$s AZw W-H$mQ> H$m jo \$b A h , _| o[aV {d wV -dmhH$ ~b (emf) Ho$ {bE ` OH$ m V H$s{OE & 14 5 A device X is connected to an ac source V = V0 sin t. The variation of voltage, current and power in one cycle is shown in the following graph : (a) Identify the device X . (b) Which of the curves A, B and C represent the voltage, current and the power consumed in the circuit ? Justify your answer. (c) How does its impedance vary with frequency of the ac source ? Show graphically. (d) Obtain an expression for the current in the circuit and its phase relation with ac voltage. OR (a) Draw a labelled diagram of an ac generator. Obtain the expression for the emf induced in the rotating coil of N turns each of cross-sectional area A, in the presence of a magnetic field B . (b) A horizontal conducting rod 10 m long extending from east to west is falling with a speed 5 0 ms 1 at right angles to the horizontal component of the Earth s magnetic field, 0 3 10 4 Wb m 2. Find the instantaneous value of the emf induced in the rod. 26. 55/1 (a) Va JmJ H$s n[a^mfm {b{IE & hmBJo g {g m V H$m Cn`moJ H$aHo$ AndV Z Ho$ {Z`_ g `m{nV H$s{OE & (b) H$me Ho$ H$sU Z H$s {H $`m mam a {IH$V: Y w{dV H$me {H$g H$ma m V {H$`m OmVm h ? O~ H$m M H$m AndV Zm H$ = 1 5 h , Vmo dm`w H$m M A Vamn > Ho$ {bE ~ y Q>a H$moU kmV H$s{OE & AWdm 15 5 P.T.O. (a) g nH $ _| aIo Xmo nVbo C mb b|gm| Ho$ g `moOZ mam {V{~ ~ ~ZZm Xem Zo Ho$ {bE {H$aU AmaoI It{ME & b|gm| H$s \$moH$g X ar Ho$ nXm| _| Bg g `moOZ H$s j_Vm Ho$ {bE ` OH$ m V H$s{OE & (b) dm`w go H$m M Ho$ g_~mh { _ go Jw OaVr h B H$moB H$me {H$aU Cg g_` `yZV_ {dM{bV hmoVr h , O~ AmnVZ H$moU H$m _mZ { _ H$moU Ho$ _mZ H$m 3 hmoVm h & 4 { _ _| H$me H$s Mmb n[aH${bV H$s{OE & (a) Define wavefront. Use Huygens principle to verify the laws of refraction. (b) How is linearly polarised light obtained by the process of scattering of light ? Find the Brewster angle for air glass interface, when the refractive index of glass = 1 5. OR 55/1 (a) Draw a ray diagram to show the image formation by a combination of two thin convex lenses in contact. Obtain the expression for the power of this combination in terms of the focal lengths of the lenses. (b) A ray of light passing from air through an equilateral glass prism 3 undergoes minimum deviation when the angle of incidence is th 4 of the angle of prism. Calculate the speed of light in the prism. 16 5

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