
	Trending ▼ ICSE CBSE 10th ISC CBSE 12th CTET GATE UGC NET Vestibulares ResFinder

CBSE Class 12 Board Exam 2020 : Physics (Series 2)

19 pages, 121 questions, 0 questions with responses, 0 total responses,

	cbse12	+Fave Message
	Profile Timeline Uploads Q & A

Home > cbse12 >

Instantly get Model Answers to questions on this ResPaper. Try now!
NEW ResPaper Exclusive!

Formatting page ...

H$moS> Z . Code No. 55/2/1 amob Z . Roll No. (I) ZmoQ> H $n`m Om M H$a b| {H$ Bg Z-n _o _w{ V n > 19 h & (II) 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| & (III) H $n`m Om M H$a b| {H$ Bg Z-n _| >37 Z h & H $n`m Z H$m C ma {bIZm ew $ H$aZo go nhbo, C ma-nwp VH$m _| 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 & (IV) (V) NOTE (I) Please check that this question paper contains 19 printed pages. (II) 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. (III) Please check that this question paper contains 37 questions. (IV) Please write down the Serial Number of the question in the answer-book before attempting it. (V) 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 .55/2/1 Maximum Marks : 70 1 P.T.O. gm_m ` {ZX}e : {Z Z{b{IV {ZX}em| H$mo ~hwV gmdYmZr go n{ T>E Am a CZH$m g Vr go nmbZ H$s{OE : (i) Bg Z-n H$mo Mma I S>m| _ | {d^m{OV {H$`m J`m h H$, I, J Am a K & (ii) Bg Z-n _| 37 Z h & g^r Z A{Zdm` h & (iii) I S> H$ Z g `m 1 go 20 VH$ A{V-bKw-C mar` Z h , `oH$ Z 1 A H$ H$m h & (iv) I S> I Z g `m 21 go 27 VH$ bKw-C mar` Z h , `oH$ Z 2 A H$m| H$m h & (v) I S> J Z g `m 28 go 34 VH$ XrK -C mar` Z h , `oH$ Z 3 A H$m| H$m h & (vi) I S> K Z g `m 35 go 37 VH$ ^r XrK -C mar` Z h , `oH$ Z 5 A H$m| H$m h & (vii) Z-n _| H$moB g_J {dH$ n Zht h & VWm{n, EH$-EH$ A H$ Ho$ Xmo Zm| _|, Xmo-Xmo A H$m| dmbo Xmo Zm| _ o, VrZ-VrZ A H$m| dmbo EH$ Z _ o VWm nm M-nm M A H$m| Ho$ VrZm| Zm| _ o Am V[aH$ {dH$ n {X`m J`m h & Eogo Zm| _| Ho$db EH$ hr {dH$ n H$m C ma Xr{OE & (viii) BgHo$ A{V[a $, Amd `H$VmZwgma, `oH$ I S> Am a Z Ho$ gmW `Wmo{MV {ZX}e {XE JE h & (ix) H $ Hw$boQ>a AWdm bm J Q>o~b Ho$ `moJ H$s AZw_{V Zht h & (x) Ohm Amd `H$ 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 (me) = 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 .55/2/1 2 General Instructions : Read the following instructions very carefully and strictly follow them : (i) This question paper comprises four Sections A, B, C and D. (ii) There are 37 questions in the question paper. All questions are compulsory. (iii) Section A Questions no. 1 to 20 are very short answer type questions, carrying 1 mark each. (iv) Section B Questions no. 21 to 27 are short answer type questions, carrying 2 marks each. (v) Section C Questions no. 28 to 34 are long answer type questions, carrying 3 marks each. (vi) Section D Questions no. 35 to 37 are also long answer type questions, carrying 5 marks each. (vii) There is no overall choice in the question paper. However, an internal choice has been provided in 2 questions of 1 mark, 2 questions of 2 marks, 1 question of three marks and all the 3 questions of five marks. You have to attempt only one of the choices in such questions. (viii) In addition to this, separate instructions are given with each section and question, wherever necessary. (ix) Use of calculators and log tables is not permitted. (x) 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 (me) = 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 .55/2/1 3 P.T.O. I S> H$ ZmoQ> : ZrMo {XE JE `oH$ Z _| g~go A{YH$ Cn`w $ {dH$ n Mw{ZE : 1. {H$gr ~m {VamoY R go g `mo{OV Am V[aH$ {VamoY Amny{V V~ H$a gH$Vm h , O~ hmo (A) (B) (C) (D) 2. 3. 4. 5. r H$m H$moB gob A{YH$V_ Ymam H$s R=r R>r r R= 2 R=0 {H$gr Ymamdmhr MmbH$ _| {H$gr {~ X na {d wV -jo Am a Ymam KZ d H$m AZwnmV H$hbmVm h (A) {VamoYH$Vm (B) MmbH$Vm (C) {VamoY (D) J{VerbVm {H$gr Bbo Q >m Z H$mo {dam_ go {H$gr Eogo jo _| _w $ {H$`m J`m h Ohm EH$g_mZ {d wV Am a Mw ~H$s` jo EH$-X gao Ho$ g_m Va H$m` aV h & `h Bbo Q >m Z (A) {H$gr gab aoIm _ o J{V H$aoJm & (B) {H$gr d m _| J{V H$aoJm & (C) p Wa ahoJm & (D) g{n bmH$ma nW _| J{V H$aoJm & `yar Vmn go A{YH$ Vmn na (A) bmoh-Mw ~H$s` nXmW {VMw ~H$s` ~Z OmVm h & (B) bmoh-Mw ~H$s` nXmW AZwMw ~H$s` ~Z OmVm h & (C) AZwMw ~H$s` nXmW bmoh-Mw ~H$s` ~Z OmVm h & (D) AZwMw ~H$s` nXmW {VMw ~H$s` ~Z OmVm h & {d WmnZ Ymam V^r Ap V d _| AmVr h O~ (A) {d wV -jo n[ad{V V hmo ahm hmoVm h & (B) Mw ~H$s` jo n[ad{V V hmo ahm hmoVm h & (C) {d wV -jo _| n[adV Z Zht hmo ahm h & (D) Mw ~H$s` jo _| n[adV Z Zht hmo ahm h & .55/2/1 1 4 1 1 1 1 SECTION A Note : 1. 2. 3. Select the most appropriate option from those given below each question : A cell of internal resistance r connected across an external resistance R can supply maximum current when (A) R=r (B) R>r r (C) R= 2 (D) R=0 In a current carrying conductor, the ratio of the electric field and the current density at a point is called (A) Resistivity (B) Conductivity (C) Resistance (D) Mobility An electron is released from rest in a region of uniform electric and magnetic fields acting parallel to each other. The electron will (A) (B) (C) (D) 4. 5. 1 1 ferromagnetic material becomes diamagnetic. ferromagnetic material becomes paramagnetic. paramagnetic material becomes ferromagnetic. paramagnetic material becomes diamagnetic. Displacement current exists only when (A) (B) (C) electric field is changing. magnetic field is changing. electric field is not changing. (D) magnetic field is not changing. .55/2/1 1 move in a straight line. move in a circle. remain stationary. move in a helical path. Above Curie temperature, a (A) (B) (C) (D) 1 5 1 P.T.O. 6. 7. 8. 9. 10. Am fY ({M{H$ gm) _| {ZXmZ Ho$ gmYZ Ho$ $n _| Cn`moJ hmoZo dmbr {d wV -Mw ~H$s` Va J| h (A) X-{H$aU| & (B) nam~ JZr {H$aU| & (C) Ada $ {H$aU| & (D) naml ` Va J| & gm ` _| {H$gr p-n g {Y S>m`moS> _o| ZoQ> Ymam hmoVr h (A) ~h g `H$ Amdoe dmhH$m| Ho$ {dgaU Ho$ H$maU & (B) A nm e Amdoe dmhH$m| Ho$ Andmh Ho$ H$maU & (C) ey ` `m|{H$ {dgaU Am a Andmh YmamE g_mZ Am a {dnarV hmoVr h & (D) ey ` `m|{H$ Amdoe dmhH$m| _| H$moB ^r g {Y H$mo nma Zht H$a nmVo h & {H$gr n- H$ma Ho$ AY MmbH$ _| XmVm D$Om Va p Wa hmoVm h (A) D$Om A Vamb Ho$ Ho$ na & (B) MmbZ ~ S> Ho$ R>rH$ ZrMo & (C) g `moOH$Vm ~ S> Ho$ R>rH$ D$na & (D) MmbZ ~ S> _| & O~ Xmo Zm{^H$ (A 10) EH$-X gao Ho$ gmW g J{bV hmoH$a EH$ ^mar Zm{^H$ ~ZmVo h , Vmo (A) ~ YZ D$Om {V `yp bAm Z _| d { hmoVr h & (B) ~ YZ D$Om {V `yp bAm Z _| H$_r hmoVr h & (C) ~ YZ D$Om {V `yp bAm Z _| H$moB n[adV Z Zht hmoVm & (D) Hw$b ~ YZ D$Om KQ> OmVr h & j` _ o (A) `yQ >m Z Eop Q> `yQ >rZmo C g{O V H$aHo$ moQ>m Z _| n[ad{V V hmo OmVm h & (B) `yQ >m Z `yQ >rZmo C g{O V H$aHo$ moQ>m Z _| n[ad{V V hmo OmVm h & (C) moQ>m Z Eop Q> `yQ >rZmo C g{O V H$aHo$ `yQ >m Z _| n[ad{V V hmo OmVm h & (D) moQ>m Z `yQ >rZmo C g{O V H$aHo$ `yQ >m Z _| n[ad{V V hmo OmVm h & 1 1 1 1 1 ZmoQ> : Cn`w $ C ma go [a $ WmZm| H$s ny{V H$s{OE : 11. 12. `{X {H$gr ~ X n > _| doe H$aZo Am a ~mha {ZH$bZo dmbo {d wV b g H $_e 2 h , Vmo Bg n > _| n[a~ ZoQ> {d wV Amdoe ___________ hmoJm & : 1 Am a ` J Ho$ { {Par `moJ _| nX} Ho$ {H$gr {~ X na `{VH$aU H$aVr Xmo Va Jm| Ho$ ~rM nWm Va 5 h , `hm Cn`moJ {H$E JE H$me H$s Va JX ` h & Bg {~ X na _________ H$mbr 2 q\ $O hmoJr & AWdm `{X ` J Ho$ { {Par `moJ _| EH$ {Par nyU V: ~ X hmo, Vmo ZE n Q>Z _ o Ho$ r` C{ > H$m H$moUr` gmB O _________ hmoJm & .55/2/1 6 1 1 1 6. Electromagnetic waves used as a diagnostic tool in medicine are (A) X-rays. (B) ultraviolet rays. (C) infrared radiation. (D) ultrasonic waves. At equilibrium, in a p-n junction diode the net current is (A) due to diffusion of majority charge carriers. (B) due to drift of minority charge carriers. (C) zero as diffusion and drift currents are equal and opposite. (D) zero as no charge carriers cross the junction. In an n-type semiconductor, the donor energy level lies (A) at the centre of the energy gap. (B) just below the conduction band. (C) just above the valance band. (D) in the conduction band. 1 9. When two nuclei (A 10) fuse together to form a heavier nucleus, the (A) binding energy per nucleon increases. (B) binding energy per nucleon decreases. (C) binding energy per nucleon does not change. (D) total binding energy decreases. 1 10. In decay, a (A) neutron converts into a proton emitting antineutrino. (B) neutron converts into a proton emitting neutrino. (C) proton converts into a neutron emitting antineutrino. (D) proton converts into a neutron emitting neutrino. 1 7. 8. Note : 11. 12. 1 1 Fill in the blanks with appropriate answer : If the electric flux entering and leaving a closed surface in air are 1 and 2 respectively, the net electric charge enclosed within the surface is ___________ . In Young s double slit experiment, the path difference between two 5 interfering waves at a point on the screen is , being wavelength of 2 the light used. The ___________ dark fringe will lie at this point. OR If one of the slits in Young s double slit experiment is fully closed, the new pattern has __________ central maximum in angular size. .55/2/1 7 1 1 1 P.T.O. 13. 14. 15. {H$gr g `w $ gy _Xeu H$s C Va {d^oXZ j_Vm Ho$ {bE Cn`moJ {H$E JE H$me H$s Va JX ` _________ hmoZr Mm{hE & 1 AY w{dV H$me {dab _m `_ go gKZ _m `_ _| J_Z H$aVm h & `{X namd{V V Am a And{V V {H$aU| EH$-X gao Ho$ b ~dV h , Vmo namd{V V H$me AmnVZ Ho$ Vb Ho$ _______ a {IH$V: Y w{dV hmoVm h & 1 bmb, Zrbo Am a nrbo H$me _ o go __________ 1 H$me H$m H$sU Z A{YH$V_ hmoVm h & ZmoQ> : {Z Z{b{IV Ho$ C ma Xr{OE : 16. 17. n Hz Amd { m Ho$ moV H$m Cn`moJ H$aZo na {H$gr `mdVu Ymam (ac) n[anW _| Ym[aVm Ho$ {H$gr g Ym[a H$s {V~mYm `m hmoVr h ? AWdm {H$gr loUr AZwZmX LCR n[anW H$s {V~mYm H$m _mZ `m hmoVm h ? C 1 1 b ~mB l H$s {H$gr MmbH$ N> S> H$mo {H$gr EH$g_mZ Mw ~H$s` jo B Ho$ g_m Va aIm J`m h & Bg N> S> H$mo Mw ~H$s` jo Ho$ AZw{Xe doJ go J{V H$am`r J`r h & Bg MmbH$ _o| o[aV {d.dm.~b H$m _mZ `m hmoJm ? 1 {H$gr AmXe oaH$ go dm{hV Ymam _| n[adV Z H$s Xa H$mo \$bZ _mZH$a Cg_| o[aV {d.dm.~b (emf) Ho$ _mZ Ho$ {dMaU H$mo Xem Zo Ho$ {bE J m \$ It{ME &$ 1 19. 3 3 10 19 J 1 20. H$me-{d wV C gO Z _| nX Xohbr Amd { m H$s n[a^mfm {b{IE & 18. D$Om Ho$ \$moQ>m Z H$s Va JX ` `m h ? 1 I S> I 21. 22. {H$gr Ymamdmhr MmbH$ _| nX Amdoe dmhH$m| H$s J{VerbVm H$s n[a^mfm {b{IE & {dlmp V H$mb Ho$ nXm| _| J{VerbVm Ho$ {bE g ~ Y m H$s{OE & AWdm {H$gr Ymamdmhr MmbH$ _| nX Bbo Q >m Zm| Ho$ Andmh doJ H$s n[a^mfm {b{IE & Ymam KZ d Am a Bbo Q >m Zm| Ho$ Andmh doJ Ho$ ~rM g ~ Y m H$s{OE & 2 2 0 8 {VamoY H$m H$moB Eo_rQ>a 1 0 A VH$ H$s Ymam _mn gH$Vm h & Bg Eo_rQ>a H$mo 5 0 A VH$ H$s Ymam _mn gH$Zo `mo ` Eo_rQ>a _| n[ad{V V H$aZo Ho$ {bE Amd `H$ e Q> {VamoY H$m _mZ kmV H$s{OE & .55/2/1 8 2 13. 14. 15. For a higher resolving power of a compound microscope, the wavelength of light used should be ___________ . 1 Unpolarised light passes from a rarer into a denser medium. If the reflected and the refracted rays are mutually perpendicular, the reflected light is linearly polarised ___________ to the plane of incidence. 1 Out of red, blue and yellow lights, the scattering of ___________ light is maximum. 1 Note : 16. 17. Answer the following : What is the impedance of a capacitor of capacitance C in an ac circuit using source of frequency n Hz ? OR 1 What is the value of impedance of a resonant series LCR circuit ? 1 A conducting rod of length l is kept parallel to a uniform magnetic field B . It is moved along the magnetic field with a velocity . What is the value of emf induced in the conductor ? 1 Draw the graph showing variation of the value of the induced emf as a function of rate of change of current flowing through an ideal inductor. 1 19. What is the wavelength of a photon of energy 3 3 10 19 J ? 1 20. Define the term threshold frequency in photoelectric emission. 1 18. SECTION B 21. Define the term mobility of charge carriers in a current carrying conductor. Obtain the relation for mobility in terms of relaxation time. 2 OR 22. Define the term drift velocity of electrons in a current carrying conductor. Obtain the relationship between the current density and the drift velocity of electrons. 2 An ammeter of resistance 0 8 can measure a current up to 1 0 A. Find the value of shunt resistance required to convert this ammeter to measure a current up to 5 0 A. 2 .55/2/1 9 P.T.O. 23. 24. 25. 26. 27. {H$gr `mdVu Ymam (ac) n[anW _| nX AZwZmX H$s Vr UVm H$s `m `m H$s{OE & (b) {H$gr loUr LCR n[anW _ o, VL = VC VR h & Bg n[anW Ho$ {bE e{ $ JwUm H$ H$m _mZ {H$VZm h ? AWdm V = V0 sin t {d.dm.~b (emf) H$m H$moB `mdVu Ymam (ac) moV Ym[aVm C Ho$ {H$gr g Ym[a go g `mo{OV h & Bg_| dm{hV Ymam (I) Ho$ {bE ` OH$ `w n H$s{OE & (i) V Am a t, VWm (ii) I Am a t Ho$ ~rM J m \$ It{ME & (a) {Z Z{b{IV {d wV -Mw ~H$s` Va Jm| _| go (a) `yZV_ Va JX ` , VWm {H$gH$s h ? BZ XmoZm| Va Jm| _| go `oH$ H$m EH$ Cn`moJ {b{IE & Ada $ Va J|, gy _ Va J|, -{H$aU| Am a X-{H$aU| {H$gr {~ ~ H$mo 60 cm dH $Vm { `m Ho$ AdVb Xn U Ho$ gm_Zo h & ~ZZo dmbo {V{~ ~ H$s H ${V Am a p W{V kmV H$s{OE & (b) 2 2 `yZV_ Amd { m 2 20 cm X ar na aIm J`m 2 JmBJa-_mg S>Z H$sU Z `moJ _ o {H$gr ^mar Zm{^H$ Ho$ Hy$bm _ jo _| Eo \$m-H$Um| H$m jon-nW AmaoI _| Xem E AZwgma h & (a) Bg AmaoI _o| b Am a {H$ZH$m {Z $nU H$aVo h (b) (i) = 0 , Am a (ii) = 180 Ho$ ? {bE b H$m _mZ `m hmoJm ? g {Y S>m`moS> Ho$ V-I A{^bmj{UH$ It{ME & n > H$s{OE {H$ n M{X{eH$ ~m`g Ho$ AYrZ Ymam H $m {VH$ dmo Q>Vm VH$ AZw `w $ dmo Q>Vm na bJ^J {Z^ a `m| Zht H$aVr h & 2 p-n .55/2/1 10 2 23. (a) Explain the term sharpness of resonance in ac circuit. (b) In a series LCR circuit, VL = VC VR. What is the value of power factor for this circuit ? 2 OR An ac source of emf V = V0 sin t is connected to a capacitor of capacitance C. Deduce the expression for the current (I) flowing in it. Plot the graph of (i) V vs. t, and (ii) I vs. t. 24. Which of the following electromagnetic waves has (a) minimum wavelength, and (b) minimum frequency ? Write one use of each of these two waves. Infrared waves, Microwaves, -rays and X-rays 25. 26. 27. 2 2 An object is kept 20 cm in front of a concave mirror of radius of curvature 60 cm. Find the nature and position of the image formed. 2 In Geiger-Marsden scattering experiment, the trajectory of -particles in Coulomb s field of a heavy nucleus is shown in the figure. (a) What do b and represent in the figure ? (b) What will be the value of b for (i) = 0 , and (ii) = 180 ? 2 Draw V-I characteristics of a p-n junction diode. Explain, why the current under reverse bias is almost independent of the applied voltage up to the critical voltage. .55/2/1 11 2 P.T.O. 28. I S> J Xmo N>moQ>o gd g_ {d wV { Y wd AB VWm CD {OZ_| `oH$ H$m { Y wd AmKyU p h , AmaoI _| Xem E AZwgma, x-Aj H$s Amoa g Ho$V H$aVo {H$gr ~m {d wV -jo E _| EH$-X gao go 120 Ho$ H$moU na p WV h & kmV H$s{OE (a) Bg `d Wm H$m { Y wd AmKyU , Am a (b) Bg na H$m` aV ZoQ> ~b-AmKyU H$m n[a_mU Am a {Xem & 3 AWdm ZrMo {XE JE AmaoI _|, kmV H$s{OE (a) ZoQ>dH $ Ho$ {~ X A Am a B Ho$ ~rM Vw ` Ym[aVm & {X`m J`m h : C1 = C5 = 8 F, C2 = C3 = C4 = 4 F. (b) ~ Q>ar mam AmnyV A{YH$V_ Amdoe, Am a (c) ZoQ>dH $ _ o g {MV Hw$b D$Om & 29. (a) (b) .55/2/1 hrQ> Q>moZ goVw Ho$ {bE g VwbZ Ho$ {V~ Y `w n H$s{OE & {H$gr _rQ>a goVw H$m n[anW AmaoI `h `m `m H$aZo Ho$ {bE It{ME {H$ _rQ>a goVw {H$g H$ma hrQ> Q>moZ goVw na AmYm[aV h & 12 3 3 SECTION C 28. Two small identical electric dipoles AB and CD, each of dipole moment p are kept at an angle of 120 to each other in an external electric field E pointing along the x-axis as shown in the figure. Find the (a) (b) dipole moment of the arrangement, and magnitude and direction of the net torque acting on it. 3 OR In the figure given below, find the 29. (a) equivalent capacitance of the network between points A and B. (b) (c) Given : C1 = C5 = 8 F, C2 = C3 = C4 = 4 F. maximum charge supplied by the battery, and total energy stored in the network. (a) Derive the condition of balance for Wheatstone bridge. (b) Draw the circuit diagram of a meter bridge to explain how it is based on Wheatstone bridge. .55/2/1 13 3 3 P.T.O. 30. AmaoI _| `mdVu Ymam (ac) moV H$s Amd { m Ho$ gmW {H$gr g Ym[a Ho$ {VKmV _ o {dMaU H$mo J m \$ mam Xem `m J`m h & (a) g Ym[a H$s Ym[aVm kmV H$s{OE & {H$gr AmXe oaH$ H$m 100 Hz Amd { m na {VKmV Bg g Ym[a H$s Cgr Amd { m na {VKmV Ho$ g_mZ h & oaH$ Ho$ oaH$ d H$m _mZ kmV H$s{OE & Amd { m Ho$ gmW Bg oaH$ Ho$ {VKmV _| {dMaU H$mo Xem Zo Ho$ {bE J m \$ It{ME & 3 {H$gr IJmobr` X aXe H$ Am a {H$gr g `w $ gy _Xeu H$s g aMZm _| `m A Va hmoVm h ? {H$gr g `w $ gy _Xeu Ho$ A{^ `H$ Am a Zo{ H$m H$s \$moH$g X [a`m H $_e: 1 25 cm Am a 5 0 cm h & O~ A {V_ {V{~ ~ {ZH$Q> {~ X na ~ZVm h , Vmo H$moUr` AmdY Z 30 m H$aZo Ho$ {bE A{^ `H$ Ho$ gmnoj {~ ~ H$s p W{V kmV H$s{OE & 3 {H$gr H$me-gwJ mhr n > na Amn{VV H$me H$s Va JX ` H$mo 1 go 2 H$aZo na Cggo C g{O V H$m{eH$-Bbo Q >m Zm| H$s A{YH$V_ J{VO D$Om X JwZr hmo OmVr h & 1 Am a 2 Ho$ nXm| _| YmVw n > Ho$ {bE Xohbr Va JX ` Am a H$m` \$bZ Ho$ {bE ` OH$ `w n H$s{OE & 3 (b) (c) 31. 32. 33. (a) {H$gr ao{S>`moEop Q>d nXmW H$s AY Am`w Am a Am gV Am`w Ho$ ~rM {d^oXZ H$s{OE & (b) H$moB ao{S>`moEop Q>d nXmW AnZr _m ` Am`w H$s Ad{Y Ho$ ~am~a g_` VH$ j{`V hmoVm h & Bg Ad{Y Ho$ n MmV Bg nXmW H$m Aj{`V eof ^mJ kmV H$s{OE & .55/2/1 14 3 30. The figure shows the graphical variation of the reactance of a capacitor with frequency of ac source. (a) (b) 31. 32. 33. Find the capacitance of the capacitor. An ideal inductor has the same reactance at 100 Hz frequency as the capacitor has at the same frequency. Find the value of inductance of the inductor. (c) Draw the graph showing the variation of the reactance of this inductor with frequency. What is the difference in the construction of an astronomical telescope and a compound microscope ? The focal lengths of the objective and eyepiece of a compound microscope are 1 25 cm and 5 0 cm, respectively. Find the position of the object relative to the objective in order to obtain an angular magnification of 30 when the final image is formed at the near point. The maximum kinetic energy of the photoelectrons emitted is doubled when the wavelength of light incident on the photosensitive surface changes from 1 to 2. Deduce expressions for the threshold wavelength and work function for the metal surface in terms of 1 and 2. (a) (b) .55/2/1 Differentiate between half-life and average life of a radioactive substance. A radioactive substance decays for an interval of time equal to its mean life. Find the fraction of the amount of the substance which is left undecayed after this time interval. 15 3 3 3 3 P.T.O. 34. gm a gob H$m `m H$m` h ? g jon _| BgH$s H$m` {d{Y H$s `m `m H$s{OE Am a BgH$m A{^bmj{UH$ dH $ It{ME & I-V 3 I S> K 35. (a) `h Xem Zo Ho$ {bE JmCg Ho$ {Z`_ H$m Cn`moJ H$s{OE {H$ { `m R Ho$ EH$g_mZ Amdo{eV {H$gr Jmobr` Imob Ho$ ~mha Imob Ho$ Ho$ go r X ar na { WV {H$gr {~ Xw na {d wV -jo H$m _mZ CVZm hr hmoVm h , {OVZm {H$ Ho$ na g nyU Amdoe H$mo gm { V _mZH$a Bgr {~ X na hmoVm & X ar r Ho$ gmW, r R Am a r R Ho$ {bE, {d wV -jo Ho$ {dMaU H$mo Xem Zo Ho$ {bE J m \$ ^r It{ME & (b) Xmo {~ X Amdoe + 1 C Am a + 4 C EH$-X gao go 30 cm X ar na p WV h & BZ XmoZm| Amdoem| H$mo {_bmZo dmbr aoIm na + 1 C Amdoe go {H$VZr X ar na ZoQ> {d wV -jo ey ` hmoJm ? AWdm (a) (b) {H$gr ~m EH$g_mZ {d wV -jo E _| Xmo {~ X Amdoe q1 Am a q2 EH$-X gao go r X ar na p WV h & Amdoem| Ho$ Bg {ZH$m` H$mo g H${bV H$aZo _| {H$`m J`m H$m` kmV H$s{OE & 20 cm ^wOm H$m H$moB KZ AmaoI _| Xem E AZwgma {H$gr jo _| aIm h & Bg jo _| H$moB {d wV -jo E Bg H$ma {d _mZ h {H$ {H$gr {~ X na {d^d H$mo Bg H$ma ` $ {H$`m OmVm h V = 10x + 5, Ohm V dmo Q _|> VWm x _rQ>a _| h & kmV H$s{OE (i) (ii) .55/2/1 5 {d wV -jo E , Am a Bg KZ go Jw OaZo dmbm Hw$b {d wV b g & 16 5 34. What is the function of a solar cell ? Briefly explain its working and draw its I-V characteristic curve. 3 SECTION D 35. (a) Use Gauss s law to show that due to a uniformly charged spherical shell of radius R, the electric field at any point situated outside the shell at a distance r from its centre is equal to the electric field at the same point, when the entire charge on the shell were concentrated at its centre. Also plot the graph showing the variation of electric field with r, for r R and r R. (b) Two point charges of + 1 C and + 4 C are kept 30 cm apart. How far from the + 1 C charge on the line joining the two charges, will the net electric field be zero ? 5 OR (a) Two point charges q1 and q2 are kept r distance apart in a uniform external electric field E . Find the amount of work done in assembling this system of charges. (b) A cube of side 20 cm is kept in a region as shown in the figure. An electric field E exists in the region such that the potential at a point is given by V = 10x + 5, where V is in volt and x is in m. Find the .55/2/1 (i) electric field E , and (ii) total electric flux through the cube. 17 5 P.T.O. 36. (a) { `m R Ho$ {H$gr d mmH$ma nme go Ymam I dm{hV hmo ahr h & Bg nme Ho$ Ho$ go BgHo$ Aj na p WV x X ar Ho$ {H$gr {~ X na Mw ~H$s` jo Ho$ {bE ` OH$ m H$s{OE & (b) 2m (a) (b) 37. (a) (b) (a) (b) .55/2/1 b ~r H$moB MmbH$ N> S> {H$gr j {VO _o O na C ma-X{jU {Xem _| aIr h & Bg_ o X{jU go C ma H$s Amoa 5 A Ymam dm{hV hmo ahr h & Bg N> S> na H$m` aV Mw ~H$s` ~b H$s {Xem Am a n[a_mU kmV H$s{OE & `h {X`m J`m h {H$ Bg WmZ na n dr H$m Mw ~H$s` jo 0 6 10 4 T VWm Z{V H$moU h & 6 AWdm {H$gr EH$g_mZ Mw ~H$s` jo _| {H$gr J doZmo_rQ>a H$s Ymamdmhr Am`VmH$ma Hw$ S>br na H$m` aV {djonH$ ~b-AmKyU Ho$ {bE ` OH$ m H$s{OE & Mb Hw$ S>br J doZmo_rQ>a _| Aar` Mw ~H$s` jo H$m Cn`moJ `m| {H$`m OmVm h ? {H$gr gmB bmoQ >m Z, {OgH$s S>r O H$s { `m 40 cm h , Ho$ mam `_mZ 1 6 10 27 kg Am a Amdoe 1 6 10 19 C Ho$ H$Um| H$mo d[aV {H$`m J`m h & Bg_| 0 4 T Ho$ Mw ~H$s` jo H$m Cn`moJ {H$`m J`m h & Bg daH$ mam H$U -nw O H$mo Xr J`r J{VO D$Om (MeV _|) kmV H$s{OE & {H$gr C^`mo mb b|g Ho$ {bE b|g _oH$a gy `w n H$s{OE & 10 cm \$moH$g X ar Ho$ {H$gr C mb b|g go 12 cm X ar na, _w ` Aj na, H$moB {~ X {H$V {~ ~ p WV h & b|g Ho$ X gar Amoa 10 cm X ar na {H$gr C mb Xn U H$mo g_mj aIm J`m h & `{X A {V_ {V{~ ~ {~ ~ Ho$ g nmVr h , Vmo {H$aU AmaoI It{ME Am a C mb Xn U H$s \$moH$g X ar kmV H$s{OE & AWdm Va JmJ {H$go H$hVo h ? `h {H$g H$ma dY Z H$aVm h & hmBJo g Ho$ {g m V H$m Cn`moJ H$aHo$ {H$gr n > go g_Vb Va JmJ Ho$ namdV Z H$s `m `m VWm namdV Z Ho$ {Z`_m| H$m g `mnZ H$s{OE & {H$gr nVbr {Par na 500 nm Va JX ` H$m nVbm (g_m Va) H$me nw O AmnVZ H$aVm h {OgHo$ \$b d $n 1 m X ar na p WV nX} na {ddV Z n Q>Z m hmoVm h & `{X nhbm {Zp Z > nX} Ho$ Ho$ go 2 5 mm X ar na ~ZVm h , Vmo (i) {Par H$s Mm S>mB , Am a (ii) nX} Ho$ Ho$ go nhbo { Vr`H$ C{ > H$s X ar kmV H$s{OE & 18 5 5 5 5 36. 37. (a) A circular loop of radius R carries a current I. Obtain an expression for the magnetic field at a point on its axis at a distance x from its centre. (b) A conducting rod of length 2 m is placed on a horizontal table in north-south direction. It carries a current of 5 A from south to north. Find the direction and magnitude of the magnetic force acting on the rod. Given that the Earth s magnetic field at the place is 0 6 10 4 T and angle of dip is . 6 OR 5 (a) Obtain the expression for the deflecting torque acting on the current carrying rectangular coil of a galvanometer in a uniform magnetic field. Why is a radial magnetic field employed in the moving coil galvanometer ? (b) Particles of mass 1 6 10 27 kg and charge 1 6 10 19 C are accelerated in a cyclotron of dee radius 40 cm. It employs a magnetic field 0 4 T. Find the kinetic energy (in MeV) of the particle beam imparted by the accelerator. 5 Derive lens maker s formula for a biconvex lens. A point object is placed at a distance of 12 cm on the principal axis of a convex lens of focal length 10 cm. A convex mirror is placed coaxially on the other side of the lens at a distance of 10 cm. If the final image coincides with the object, sketch the ray diagram and find the focal length of the convex mirror. 5 OR What is a wavefront ? How does it propagate ? Using Huygens principle, explain reflection of a plane wavefront from a surface and verify the laws of reflection. A parallel beam of light of wavelength 500 nm falls on a narrow slit and the resulting diffraction pattern is obtained on a screen 1 m away. If the first minimum is formed at a distance of 2 5 mm from the centre of the screen, find the (i) width of the slit, and (ii) distance of first secondary maximum from the centre of the screen. 5 (a) (b) (a) (b) .55/2/1 19 P.T.O.

Formatting page ...

Tags : cbse, cbse papers, cbse sample papers, cbse books, portal for cbse india, cbse question bank, central board of secondary education, cbse question papers with answers, prelims preliminary exams, pre board exam papers, cbse model test papers, solved board question papers of cbse last year, previous years solved question papers, free online cbse solved question paper, cbse syllabus, india cbse board sample questions papers, last 10 years cbse papers, cbse question papers 2017, cbse guess sample questions papers, cbse important questions, specimen / mock papers 2018.

cbse12 chat

Horizontal lines at:
Guest Horizontal lines at:
AutoRM Data:
Box geometries: