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CBSE Class 12 Board Exam 2019 : Physics (Series 5)

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SET-1 H$moS> Z . Series BVM/5 Code No. amob Z . 55/5/1 narjmWu H$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 > 19 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 _| >27 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 19 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 27 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 55/5/1 Maximum Marks : 70 1 P.T.O. gm_m ` {ZX}e : (i) g^r Z A{Zdm` h & Bg Z-n _| Hw$b 27 Z h & (ii) Bg Z-n Ho$ Mma ^mJ h : I S> A, I S> ~, I S> g Am a I S> X & (iii) I S> A _| nm M Z h , `oH$ H$m EH$ A H$ h & I S> ~ _| gmV Z h , `oH$ Ho$ Xmo A H$ h & I S> g _| ~mah Z h , `oH$ Ho$ VrZ A H$ h Am a I S> X _| VrZ Z h , `oH$ Ho$ nm M A H$ h & (iv) Z-n _| g_J na H$moB {dH$ n Zht h & VWm{n, EH$ A H$ dmbo Xmo Zm| _|, Xmo A H$m| dmbo Xmo Zm| _|, VrZ A H$m| dmbo Mma Zm| _| 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$Vo h c = 3 108 m/s h = 6.63 10 34 Js e = 1.6 10 19 C 0 = 4 10 7 T m A 1 0 = 8.854 10 12 C2 N 1 m 2 1 4 = 9 109 N m2 C 2 0 Bbo Q >m Z H$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 55/5/1 2 : General Instructions : (i) All questions are compulsory. There are 27 questions in all. (ii) This question paper has four sections : Section A, Section B, Section C and Section D. (iii) Section A contains five questions of one mark each, Section B contains seven questions of two marks each, Section C contains twelve questions of three marks each, Section D contains three questions of five marks each. (iv) There is no overall choice. However, an internal choice(s) has been provided in two questions of one mark, two questions of two marks, four questions of three marks and 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 (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 55/5/1 3 P.T.O. I S> A SECTION A 1. {H$gr Amdo{eV MmbH$ Imob Ho$ ^rVa BgHo$ g_ V Am`VZ _| p Wa d wV {d^d {Z`V `m| ahVm h ? 1 Why is the electrostatic potential inside a charged conducting shell constant throughout the volume of the conductor ? 2. AZwMw ~H$s` nXmW H$m EH$ _h dnyU JwUY_ {b{IE & AWdm `m {VMw ~H$s` nXmWm] _| ~m Mw ~H$s` jo H$s AZwnp W{V _| {H$gr na_mUw _| n[aUm_r Mw ~H$s` AmKyU hmoVm h ? 1 1 Write one important property of a paramagnetic material. OR Do the diamagnetic substances have resultant magnetic moment in an atom in the absence of external magnetic field ? 3. {H$gr moQ>m Z go g ~ Xo-~ m br Va JX ` Am a CgHo$ g doJ Ho$ ~rM J m\$ It{ME & 1 Plot a graph of the de-Broglie wavelength associated with a proton versus its momentum. 4. O~ {H$gr p-n g {Y S>m`moS> Ho$ {gam| na AmaoI _| Xem E AZwgma {g Zb bJm`m J`m h , Vmo {ZJ V {g Zb H$m AmaoI It{ME & 10 V H$m dJ {Zdoer Draw the output signal in a p-n junction diode when a square input signal of 10 V as shown in the figure is applied across it. 55/5/1 4 1 5. AmaoI _| Xem E JE JoQ>m| Ho$ g `moOZ Ho$ n[anW Ho$ Vw ` JoQ> H$mo nhMm{ZE Am a BgH$m VrH$ {b{IE & 1 AWdm Xem E JE JoQ>m| Ho$ g `moOZ Ho$ JoQ> H$m VH $ VrH$ It{ME Am a CgH$m Zm_ {b{IE & 1 Identify the equivalent gate for the circuit of a combination of gates shown in the figure. Write its symbol. OR Draw the logic symbol of the gate shown by the combination of gates and write its name. I S> ~ SECTION B 6. p Ho$ {H$gr {d wV { Y wd na H$m` aV {H$gr EH$g_mZ {d wV -jo E _| { Y wd AmKyU ~b-AmKyU Ho$ {bE ` OH$ `w n H$s{OE & AWdm { Y wd AmKyU p Ho$ {H$gr {d wV { Y wd Ho$ Aj na p WV {H$gr {~ X na {d wV -jo Ho$ {bE ` OH$ `w n H$s{OE & Cg p W{V Ho$ {bE ^r ` OH$ {b{IE O~ X ar r >> { Y wd H$s b ~mB a go & 55/5/1 5 2 2 P.T.O. Derive an expression for the torque acting on an electric dipole of dipole moment p placed in a uniform electric field E . Write the direction along which the torque acts. OR Derive an expression for the electric field at a point on the axis of an electric dipole of dipole moment p . Also write its expression when the distance r >> the length a of the dipole. 7. loUr _| g `mo{OV 12 pF Ho$ Xmo gd g_ g Ym[a 50 V H$s ~ Q>ar Ho$ {gam| go Ow S>o h & Bg g `moOZ _| g {MV p Wa d wV D$Om n[aH${bV H$s{OE & `{X `o g Ym[a nm d H $_ _| g `mo{OV hmoH$a Bgr ~ Q>ar go Ow S>o h , Vmo Bg g `moOZ _| g {MV D$Om H$m _mZ kmV H$s{OE & 2 Two identical capacitors of 12 pF each are connected in series across a 50 V battery. Calculate the electrostatic energy stored in the combination. If these were connected in parallel across the same battery, find out the value of the energy stored in this combination. 8. n gd g_ {VamoYH$m|, {OZ_| `oH$ H$m {VamoY R h , Ho$ {H$gr g_w ` Ho$ loUr g `moOZ H$m ^mdr {VamoY X h & O~ B h| nm d _| g `mo{OV H$aVo h , Vmo CZH$m ^mdr {VamoY Y hmo OmVm h & X Am a Y H$m JwUH$ kmV H$s{OE & 2 A set of n identical resistors, each of resistance R when connected in series have an effective resistance X . When they are connected in parallel, their effective resistance becomes Y . Find out the product of X and Y. 9. { `m R H$s Xmo gd g_ Hw$ S>{b`m P Am a Q b ~dV Vbm| _| Bg H$ma aIr h {H$ BZHo$ Ho$ C^`{Z R> h & `{X BZ Hw$ S>{b`m| go H $_e: I Am a 3 I Ymam dm{hV hmo ahr h , Vmo C^`{Z R> Ho$ na Mw ~H$s` jo H$m n[a_mU Am a {Xem kmV H$s{OE & 55/5/1 6 2 Two identical coils P and Q each of radius R are lying in perpendicular planes such that they have a common centre. Find the magnitude and direction of the magnetic field at the common centre when they carry currents equal to I and 3 I respectively. 10. (a) dh {V~ Y m V H$s{OE {Og_| {H$gr Mw ~H$s` jo go Jw OaVo g_` {H$gr Bbo Q >m Z _| H$moB {dMbZ Zht hmoVm & (b) g_mZ Mmb go J{V_mZ Xmo moQ>m Z B2 P Am a Q B1 H $_e: Xmo Mw ~H$s` jo m| | B 2 | > | B1 | go BZ jo {XemAm| Ho$ b ~dV J{V H$a aho h & `{X BZ_| go H$m Z-gm moQ>m Z N>moQ>r { `m Ho$ d mr` nW na J_Z H$aoJm H$s{OE & ? Am a h , Vmo `m `m 2 (a) Obtain the conditions under which an electron does not suffer any deflection while passing through a magnetic field. (b) Two protons P and Q moving with the same speed pass through the magnetic fields B1 and B 2 respectively, at right angles to the field directions. If | B 2 | > | B1 |, which of the two protons will describe the circular path of smaller radius ? Explain. 11. {H$gr Am`m_ _m Sw>{bV Va J _| Xmo nm d ~ S>m| H$s Amd { m`m H $_e: 640 kHz Am a 660 kHz h & dmhH$ Am a _m Sw>bH$ {g Zbm| H$s Amd { m`m kmV H$s{OE & Am`m_ _m Sw>bZ _| Amd `H$ ~ S> Mm S>mB H$m _mZ ^r m V H$s{OE & $ AWdm 0 3 _m Sw>bZ gyMH$m H$ Ho$ gmW 10 kHz `mdH $s` dmo Q>Vm mam {H$gr `mdH $s` dmhH$ dmo Q>Vm H$m Am`m_ _m Sw>bZ {H$`m J`m h & `{X dmhH$ Va J H$s Amd { m 10 MHz VWm BgH$m Am`m_ 40 V h , Vmo Xmo nm d ~ S>m| H$s Amd { m Am a Am`m_ n[aH${bV H$s{OE & 55/5/1 7 2 2 P.T.O. The frequencies of two side bands in an amplitude modulated wave are 640 kHz and 660 kHz respectively. Find the frequencies of the carrier and the modulating signals. Also obtain the value of the bandwidth required in amplitude modulation. OR A sinusoidal carrier voltage is amplitude modulated by a sinusoidal voltage of 10 kHz with modulation index 0 3. If the carrier frequency is 10 MHz and its amplitude is 40 V, calculate the frequency and amplitude of the two sidebands. 12. {H$gr `mnH$ g Mma `d Wm H$m bm H$ AmaoI It{ME Am a Ho$ H$m` {b{IE & (i) o{f , Am a (ii) A{^J mhr 2 Draw a block diagram of a generalized communication system and write the functions of (i) a transmitter, and (ii) a receiver. I S> g SECTION C 13. {H$gr Amdoe Q H$mo Xmo g Ho$ r ImoIbo Jmobm|, {OZH$s { `mE r VWm R (R >> r) h , na Bg H$ma {dV[aV {H$`m J`m h {H$ BZHo$ n R>r` Amdoe KZ d g_mZ h & BZHo$ C^`{Z R> Ho$ na {d^d Ho$ {bE ` OH$ `w n H$s{OE & AWdm Am a c (a < b < c) { `mAm| Ho$ VrZ g Ho$ r Ymp dH$ Imobm| A, B Am a C Ho$ n R>r` Amdoe KZ d H $_e:, Xem E AZwgma, + , Am a + h & (a) VrZm| Imobm| A, B Am a C Ho$ {d^d Ho$ {bE ` OH$ m V H$s{OE & (b) `{X Imob A Am a C g_mZ {d^d na h , Vmo a, b Am a c _| g ~ Y m V H$s{OE & 3 a, b 55/5/1 8 3 A charge Q is distributed over the surfaces of two concentric hollow spheres of radii r and R (R >> r), such that their surface charge densities are equal. Derive the expression for the potential at the common centre. OR Three concentric metallic shells A, B and C of radii a, b and c (a < b < c) have surface charge densities + , and + respectively as shown. 14. (a) Obtain the expressions for the potential of three shells A, B and C. (b) If shells A and C are at the same potential, obtain the relation between a, b and c. Mb Hw$ S>br J d Zmo_rQ>a H$m {g m V {b{IE & BgH$s H$m` {d{Y H$s `m `m H$s{OE VWm BgH$s Hw$ S>br _| Ymam dm{hV {H$E OmZo na C n hmoZo dmbo {djonU Ho$ {bE ` OH$ m V H$s{OE & Ymam gwJ m{hVm H$s n[a^mfm {b{IE & 3 AWdm `m `m H$s{OE {H$ {H$gr J d Zmo_rQ>a H$mo {XE JE n[aga Ho$ Eo_rQ>a _| {H$g H$ma n[ad{V V {H$`m Om gH$Vm h & e Q> {VamoY Am a nyU n _mZm {djonU Ho$ {bE Ymam Ho$ {bE ` OH$ `w n H$s{OE & Eo_rQ>a H$m ^mdr {VamoY kmV H$s{OE & 3 State the principle of a moving coil galvanometer. Explain its working and obtain the expression for the deflection produced due to the current passed through the coil. Define current sensitivity. OR Explain how a galvanometer can be converted into an ammeter of a given range. Derive an expression for shunt resistance and current for full scale deflection. Find the effective resistance of the ammeter. 55/5/1 9 P.T.O. 15. {H$gr loUr LCR n[anW na H$moB dmo Q>Vm v = vm sin t AZw `w $ H$aZo na n[anW _| dm{hV Ymam H$m _mZ i = im sin ( t + ) h & moV mam AmnyV Vm j{UH$ e{ $ Ho$ {bE ` OH$ `w n H$s{OE & Bg H$ma Am gV e{ $ Ho$ {bE ` OH$ m V H$s{OE & nXm| e{ $ JwUm H$ Am a dmQ>hrZ Ymam H$s n[a^mfm, Eogo CXmhaUm| H$mo XoVo h E {OZ_| e{ $ JwUm H$ A{YH$V_ hmo VWm Eogm n[anW hmo {Og_| dmQ>hrZ Ymam hmo, H$s{OE & 3 A voltage v = vm sin t applied to a series LCR circuit, drives a current in the circuit given i = im sin ( t + ). Deduce the expression for the instantaneous power supplied by the source. Hence, obtain the expression for the average power. Define the terms power factor and wattless current , giving the examples where power factor is maximum and the circuit where there is wattless current. 16. {d WmnZ Ymam H$s n[a^mfm {b{IE & dc moV mam {H$gr g Ym[a H$mo Amdo{eV H$aVo g_` BgH$s `m ^y{_H$m hmoVr h ? `m {d WmnZ Ymam H$m _mZ MmbZ Ymam Ho$ g_mZ hmoVm h ? `m `m H$s{OE & 3 Define displacement current. What role does it play while charging a capacitor by dc source. Is the value of displacement current same as that of the conduction current ? Explain. 17. H$moB nXm {H$gr {~ ~ go 90 cm H$s X ar na p WV h & {H$gr C mb b|g mam b|g H$s Xmo {d{^ p W{V`m|, {OZHo$ ~rM 20 cm H$m n WH$Z h , Ho$ {bE {~ ~ H$m nX} na {V{~ ~ ~ZVm h & b|g H$s \$moH$g X ar n[aH${bV H$s{OE & 3 AWdm 20 cm \$moH$g X ar H$m H$moB C mb b|g 15 cm \$moH$g X ar Ho$ {H$gr AdVb b|g go 30 cm X ar na p WV h VWm BZ XmoZm| b|gm| Ho$ _w ` Aj g nmVr h & O~ H$moB {~ ~ C mb b|g Ho$ gm_Zo 30 cm X ar na p WV h , Vmo g `moOZ mam ~Zo A {V_ {V{~ ~ H$s p W{V n[aH${bV H$s{OE & `{X Bg {~ ~ H$mo AdVb b|g Ho$ gm_Zo 30 cm X ar na aIm OmVm Vmo `m Bg n[aUm_ _| H$moB A Va hmoVm ? H$maU Xr{OE & 55/5/1 10 3 A screen is placed 90 cm from an object. The image of the object on the screen is formed by a convex lens at two different positions separated by 20 cm. Calculate the focal length of the lens. OR A convex lens of focal length 20 cm and a concave lens of focal length 15 cm are kept 30 cm apart with their principal axes coincident. When an object is placed 30 cm in front of the convex lens, calculate the position of the final image formed by the combination. Would this result change if the object were placed 30 cm in front of the concave lens ? Give reason. 18. 19. (a) Va JmJ H$s n[a^mfm {b{IE & hmBJo g H$s `m{_Vr` g aMZm H$m Cn`moJ H$aVo h E AmaoI H$s ghm`Vm go `h `m `m H$s{OE {H$ dm`w _| H$moB g_Vb Va JmJ jU t1 go t2 VH$ {H$g H$ma J_Z H$aVm h & (b) {H$gr C mb b|g na H$moB g_Vb Va JmJ AmnVZ H$aVm h & AmaoI H$s ghm`Vm go ~ZZo dmbo And{V V Va JmJ H$s `m `m H$s{OE & (a) Define a wavefront. Using Huygens geometrical construction, explain with the help of a diagram how the plane wavefront travels from the instant t1 to t2 in air. (b) A plane wavefront is incident on a convex lens. Explain, with the help of the diagram, the shape of the refracted wavefront formed. (a) `m `m H$s{OE {H$ gmYmaU a JrZ H$m M Ho$ Yyn Ho$ M _m| H$s VwbZm _| nmoboam BS>m| Ho$ ~Zo A N>r JwUVm Ho$ Yyn Ho$ M _m| H$mo dar`Vm `m| Xr OmVr h & (b) g_Vb Y w{dV H$me H$s n[a^mfm {b{IE & (c) {H$gr nmoboam BS> go H$moB g_Vb Y w{dV H$me nw O Jw Omam J`m h & nmoboam BS> Ho$ KyU Z H$moU Ho$ gmW nmaJ{_V H$me H$s Vrd Vm Ho$ {dMaU H$mo Xem Zo Ho$ {bE J m \$ It{ME & (a) Good quality sunglasses made of polaroids are preferred over ordinary coloured glasses. Explain why. (b) How is plane polarized light defined ? (c) A beam of plane polarised light is passed through a polaroid. Show graphically, variation of the intensity of the transmitted light with angle of rotation of the polaroid. 55/5/1 11 3 3 P.T.O. 20. {H$gr {XE JE H$me-gwJ mhr nXmW H$mo Amd { m v Ho$ H$me mam {H$a{UV {H$E OmZo na C g{O V \$moQ>moBbo Q >m Zm| H$s A{YH$V_ Mmb Vmax h & {XE JE AmaoI _| J m\$ _| Amd { m 2 (v) Ho$ gmW Vmax Ho$ {dMaU H$mo Xem `m J`m h & {Z Z{b{IV Ho$ {bE ` OH$ m V H$s{OE : (a) bm H$ {Z`Vm H$, VWm (b) mMbm| l , n Am a Bbo Q >m Z Ho$ `_mZ m Ho$ nXm| _| H$me-gwJ mhr nXmW H$m H$m` \$bZ & (c) Bg J m\$ mam Xohbr Amd { m {H$g H$ma {ZYm [aV H$aVo h ? When a given photosensitive material is irradiated with light of frequency v, the maximum speed of the emitted photoelectrons equals 2 Vmax. The graph shown in the figure gives a plot of Vmax varying with frequency v. Obtain an expression for (a) Planck s constant, and (b) The work function of the given photosensitive material in terms of the parameters l , n and the mass m of the electron. (c) How is threshold frequency determined from the plot ? 55/5/1 12 3 21. {H$gr `yAm Zr hmBS >moOZ na_mUw, AWm V Eogm na_mUw {Og_| Bbo Q >m Z H$m {V WmnZ {H$gr G$Umdo{eV `yAm Z ( ) {OgH$m `_mZ bJ^J 207 me h Am a moQ>m Z Ho$ Mmam| Amoa M H$a bJm ahm h , H$s W_ ~moh a { `m Am a {Z ZV_ Ad Wm D$Om m V H$s{OE & ({X`m J`m h hmBS >moOZ na_mUw Ho$ {bE W_ H$jm H$s { `m VWm {Z ZV_ Ad Wm D$Om H $_e: 0 53 10 10 m VWm 13 6 eV h ) 3 Obtain the first Bohr s radius and the ground state energy of a muonic hydrogen atom i.e. an atom where the electron is replaced by a negatively charged muon ( ) of mass about 207 me that orbits around a proton. (Given for hydrogen atom, radius of first orbit and ground state energy are 0 53 10 10 m and 13 6 eV respectively) 22. (a) `oH$ H$m EH$-EH$ CXmhaU XoVo h E g_ Wm{ZH$m| Am a g_^m[aH$m| Ho$ ~rM {d^oXZ H$s{OE & (b) {H$gr Zm{^H$ H$m `_mZ CgHo$ g KQ>H$m| Ho$ `_mZm| Ho$ `moJ\$b go gX d hr H$_ `m| hmoVm h ? AnZo C ma H$s nwp Q> CXmhaU XoH$a H$s{OE & 3 AWdm (a) {Z Z{b{IV N>h `yp bAmBS>m| H$m dJuH$aU (iii) g_^m[aH$ _| H$s{OE : (i) g_ `yQ >m Zr, (ii) g_ Wm{ZH$, Am a 12 C , 3 He , 198 Hg , 3 H , 197 Au , 14 C 6 2 1 79 6 80 (b) {H$gr Zm{^H$ H$m gmB O CgH$s `_mZ g `m na {H$g H$ma {Z^ a H$aVm h ? Bg H$ma `m `m H$s{OE {H$ {H$gr Zm{^H$s` nXmW H$m KZ d Zm{^H$ Ho$ gmB O na {Z^ a `m| Zht hmoZm Mm{hE & (a) Distinguish between isotopes and isobars, giving one example for each. (b) Why is the mass of a nucleus always less than the sum of the masses of its constituents ? Write one example to justify your answer. 3 OR 55/5/1 13 P.T.O. (a) Classify the following six nuclides into (i) isotones, (ii) isotopes, and (iii) isobars : 12 C , 3 He , 198 Hg , 3 H , 197 Au , 14 C 6 2 1 79 6 80 (b) 23. How does the size of a nucleus depend on its mass number ? Hence explain why the density of nuclear matter should be independent of the size of the nucleus. AmaoI _| n M{X{eH$ ~m`g _| MmbZ Ho$ {bE A{^H$p nV {H$gr AY MmbH$ S>m`moS> H$m V-I A{^bmj{UH$ Xem `m J`m h & (a) (b) Cn`moJ {H$E JE AY MmbH$ S>m`moS> H$mo nhMm{ZE & Bg `w{ $ mam {XE JE A{^bmj{UH$ H$mo m V H$aZo Ho$ {bE n[anW AmaoI It{ME & Bg `w{ $ Ho$ EH$ Cn`moJ H$s g jon _| `m `m H$s{OE & (c) The figure shows the V-I characteristic of a semiconductor diode designed to operate under reverse bias. (a) (b) (c) 55/5/1 Identify the semiconductor diode used. Draw the circuit diagram to obtain the given characteristics of this device. Briefly explain one use of this device. 14 3 24. (a) gmB O Am a _mXZ Ho$ Va Ho$ AmYma na {H$gr ~rM {d^oXZ H$s{OE & n-p-n (b) A VaU A{^bmj{UH$ It{ME Am a `h Xem BE {H$ Bg A{^bmj{UH$ H$m H$m Z-gm ^mJ dY Z Ho$ {bE Cn`moJ {H$`m OmVm h Am a `m| & Q >m { O Q>a Ho$ VrZ I S>m| Ho$ (a) Differentiate between three segments of an n-p-n transistor on the basis of their size and level of doping. (b) Draw a plot of transfer characteristic and show which portion of the characteristic is used in amplification and why. 3 I S> X SECTION D 25. (a) {H$gr gob, {Oggo H$moB Ymam I br Om ahr h , Ho$ {bE Am V[aH$ {VamoY, {d.dm. ~b (emf) Am a Q>{_ Zb {d^dm Va Ho$ ~rM g ~ Y `w n H$s{OE & gob Ho$ {bE V Am a I Ho$ ~rM J m\$ It{ME Am a BgHo$ _h d H$s `m `m H$s{OE & (b) 998 {VamoY H$m H$moB dmo Q>_rQ>a 2 V {d.dm. ~b (emf) Am a 2 Am V[aH$ {VamoY Ho$ {H$gr gob Ho$ {gam| go g `mo{OV h & dmo Q>_rQ>a Ho$ {gam| Ho$ ~rM VWm gob Ho$ Q>{_ Zbm| Ho$ ~rM ^r {d^dm Va kmV H$s{OE & dmo Q>_rQ>a Ho$ nmR> m H$ _| {VeV w{Q> H$m AmH$bZ H$s{OE & 5 AWdm (a) {d{^ {d.dm. ~b (emf) Am a Am V[aH$ {VamoYm| Ho$ Xmo gob EH$-X gao Ho$ gmW nm d _| g `mo{OV h & Bg g `moOZ Ho$ Vw ` {d.dm. ~b (emf) Am a Vw ` Am V[aH$ {VamoY Ho$ {bE ` OH$ `w n H$s{OE & (b) {d.dm. ~b (emf) 1 5 V Am a Am V[aH$ {VamoY r Ho$ Xmo gd g_ gob nm d _| g `mo{OV h VWm nm d _| g `mo{OV 17 Ho$ Xmo gd g_ {VamoYm| Ho$ g `moOZ dmbo ~m n[anW H$mo Ymam XmZ H$a aho h & A{V C {VamoY H$m H$moB dmo Q>_rQ>a gob H$s Q>{_ Zb dmo Q>Vm 1 4 V _mnVm h & `oH$ gob H$m Am V[aH$ {VamoY n[aH${bV H$s{OE & 55/5/1 15 5 P.T.O. (a) Derive a relation between the internal resistance, emf and terminal potential difference of a cell from which current I is drawn. Draw V vs I graph for a cell and explain its significance. (b) A voltmeter of resistance 998 is connected across a cell of emf 2 V and internal resistance 2 . Find the potential difference across the voltmeter and also across the terminals of the cell. Estimate the percentage error in the reading of the voltmeter. OR 26. (a) Two cells of different emfs and internal resistances are connected in parallel with one another. Derive the expression for the equivalent emf and equivalent internal resistance of the combination. (b) Two identical cells of emf 1 5 V and internal resistance r are each connected in parallel providing a supply to an external circuit consisting of two resistances of 17 each joined in parallel. A very high resistance voltmeter reads the terminal voltage of the cell to be 1 4 V. Calculate the internal resistance of each cell. (a) b ~mB l Am a {VamoY R H$s H$moB YmVw H$s N> S> Amd { m v go KyU Z H$am`r OmVr h & Bg N> S> H$m EH$ {gam Ho$ na H$sb{H$V h VWm X gam {gam { `m l Ho$ d mr` Ymp dH$ db` H$s n[a{Y na h & `h N> S> Cg Aj Ho$ n[aV: KyU Z H$aVr h Omo db` Ho$ Ho$ go Jw OaVm h VWm db` Ho$ Vb Ho$ b ~dV h & Aj Ho$ g_m Va H$moB {Z`V Am a EH$g_mZ Mw ~H$s` jo B ha WmZ na Cnp WV h & (i) N> S> _| o[aV {d.dm. ~b (emf) Am a Ymam Ho$ {bE ` OH$ `w n H$s{OE & (ii) Mw ~H$s` jo Am a N> S> _| dm{hV Ymam Ho$ H$maU Bg N> S> na H$m` aV ~b Ho$ n[a_mU Am a {Xem Ho$ {bE ` OH$ kmV H$s{OE & (iii) Bg H$ma, N> S> H$mo Ky{U V H$amZo Ho$ {bE Amd `H$ e{ $ Ho$ {bE ` OH$ m V H$s{OE & (b) {H$gr Vm ~o H$s Hw$ S>br H$mo {H$gr Mw ~H$s` jo go EH$ {Z`V doJ go ~mha {ZH$mbm J`m h & `{X Bg Hw$ S>br Ho$ Amo_r {VamoY _| d { H$a Xr OmE, Vmo `m Bg Hw$ S>br H$mo Bgr jo go ~mha {ZH$mbZm gab hmoJm ? AWdm 55/5/1 16 5 (a) H$moB Am`VmH$ma Hw$ S>br {H$gr EH$g_mZ Mw ~H$s` jo _| KyU Z H$a ahr h & {H$gr ^r jU na o[aV {d.dm. ~b (emf) Am a Ymam Ho$ {bE ` OH$ m V H$s{OE & BZHo$ {eIa _mZ ^r kmV H$s{OE & J m\$ na KyU Z H$moU ( t) Ho$ gmW o[aV {d.dm. ~b (emf) Ho$ {dMaU H$mo Xem BE & (b) Vm ~o Ho$ ~Zo _moQ>o ~obZmH$ma Imob Ho$ ImoIbo jo go hmoH$a {JaVr h B H$moB bmoho H$s N> S> {H$gr _ XH$ ~b H$m AZw^d H$aVr h & bmoho H$s N> S> H$s H ${V Ho$ {df` _| Amn `m {Z H$f {ZH$mb gH$Vo h ? `m `m H$s{OE & (a) 5 A metallic rod of length l and resistance R 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 of radius l , 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. (b) (i) Derive the expression for the induced emf and the current in the rod. (ii) Due to the presence of current in the rod and of the magnetic field, find the expression for the magnitude and direction of the force acting on this rod. (iii) Hence, obtain an expression for the power required to rotate the rod. A copper coil is taken out of a magnetic field with a fixed velocity. Will it be easy to remove it from the same field if its ohmic resistance is increased ? OR (a) A rectangular coil rotates in a uniform magnetic field. Obtain an expression for induced emf and current at any instant. Also find their peak values. Show the variation of induced emf versus angle of rotation ( t) on a graph. (b) An iron bar falling through the hollow region of a thick cylindrical shell made of copper experiences a retarding force. What can you conclude about the nature of the iron bar ? Explain. 55/5/1 17 P.T.O. 27. (a) (b) (c) Cg p W{V Ho$ {bE {H$gr g `w $ gy _Xeu H$m Zm_m {H$V {H$aU AmaoI It{ME {Og_| A {V_ {V{~ ~ n Q> Xe Z H$s A nV_ X ar na ~ZVm h & BgH$m A{^ `H$, Zo{ H$m H$s VwbZm _| bKw \$moH$g X ar Am a bKw maH$ H$m `m| hmoVm h ? `m `m H$s{OE & A{^ `H$ H$s \$moH$g X ar 4 cm h , O~{H$ Zo{ H$m H$s \$moH$g X ar 10 cm h & {~ ~ A{^ `H$ b|g go 6 cm X ar na p WV h & (i) `{X BgH$m A {V_ {V{~ ~ {ZH$Q> {~ X na ~ZVm h , Vmo g `w $ gy _Xeu H$s AmdY Z j_Vm n[aH${bV H$s{OE & (ii) g `w $ gy _Xeu H$s b ~mB ^r n[aH${bV H$s{OE & 5 AWdm (a) (b) Zm_m {H$V {H$aU AmaoI H$s ghm`Vm go H $goJ oZ namdVu X aXe H$ H$s g aMZm Am a H$m` {d{Y H$s `m `m H$s{OE & H$moB A drU IJmobk AnZo An[a H $V X aXe H$, {OgHo$ A{^ `H$ b|g H$s \$moH$g X ar 200 cm Am a Zo{ H$m H$s \$moH$g X ar 10 cm h , H$m Cn`moJ H$aHo$ gy` Ho$ gmB O H$m g{ H$Q> AmH$bZ H$aZm MmhVm h & A{^ `H$ go Zo{ H$m H$s X ar g_m`mo{OV H$aHo$ dh gy` H$m {V{~ ~ Zo{ H$m go 40 cm X ar na p WV nX} na m V H$aVm h & gy` Ho$ {V{~ ~ H$m `mg 6 0 cm h & gy` Ho$ gmB O H$m AmH$bZ H$s{OE & ({X`m J`m h {H$ gy` go n dr Ho$ ~rM H$s Am gV X ar = 1 5 1011 m) (a) Draw a labelled ray diagram of compound microscope, when final image forms at the least distance of distinct vision. (b) Why is its objective of short focal length and of short aperture, compared to its eyepiece ? Explain. (c) The focal length of the objective is 4 cm while that of eyepiece is 10 cm. The object is placed at a distance of 6 cm from the objective lens. (i) Calculate the magnifying power of the compound microscope, if its final image is formed at the near point. (ii) Also calculate length of the compound microscope. OR 55/5/1 18 5 (a) With the help of a labelled ray diagram, explain the construction and working of a Cassegrain reflecting telescope. (b) An amateur astronomer wishes to estimate roughly the size of the Sun using his crude telescope consisting of an objective lens of focal length 200 cm and an eyepiece of focal length 10 cm. By adjusting the distance of the eyepiece from the objective, he obtains an image of the Sun on a screen 40 cm behind the eyepiece. The diameter of the Sun s image is measured to be 6 0 cm. Estimate the Sun s size, given that the average Earth-Sun distance is 1 5 1011 m. 55/5/1 19 P.T.O.

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