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CBSE Class XII 2014 : PHYSICS

16 pages, 103 questions, 6 questions with responses, 6 total responses,

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H$moS> Z . Series OSR Code No. amob Z . 55/2/1 narjmWu H$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 _| >30 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 30 questions. Please write down the Serial Number of the question before attempting it. 15 minutes 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 : (i) g^r Z A{Zdm` h & (ii) Bg Z-n _| Hw$b 30 Z h & Z g . 1 go 8 VH$ Ho$ Z A{V-bKwC mar` Z h Am a `oH$ EH$ A H$ H$m h & (iii) Z g . 9 go 18 _| `oH$ Z Xmo A H$ H$m h , Z g . 19 go 27 _| `oH$ Z VrZ A H$ H$m h Am a Z g . 28 go 30 _| `oH$ Z nm M A H$ H$m h & (iv) VrZ A H$m| dmbo Zm| _| go EH$ _y `naH$ Z h & (v) 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 & (vi) H $bHw$boQ>a Ho$ Cn`moJ H$s AZw_{V Zht h & VWm{n `{X Amd `H$ hmo Vmo Amn bKwJUH$s` gma{U`m| H$m `moJ H$a gH$Vo h & (vii) Ohm Amd `H$ hmo Amn {Z Z{b{IV ^m {VH$ {Z`Vm H$m| Ho$ _mZm| H$m Cn`moJ H$a gH$Vo h : c = 3 108 m/s h = 6.63 10 34 Js e = 1.6 10 19 C o = 4 10 7 T mA 1 1 = 9 109 N m2 C 2 4 o me = 9.1 10 31 kg General Instructions : (i) All questions are compulsory. (ii) There are 30 questions in total. Questions No. 1 to 8 are very short answer type questions and carry one mark each. (iii) Questions No. 9 to 18 carry two marks each, questions no. 19 to 27 carry three marks each and questions no. 28 to 30 carry five marks each. (iv) One of the questions carrying three marks weightage is value based question. 55/2/1 2 (v) There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all three questions of five marks each weightage. You have to attempt only one of the choices in such questions. (vi) Use of calculators is not permitted. However, you may use log tables if necessary. (vii) You may use the following values of physical constants wherever necessary : c = 3 108 m/s h = 6.63 10 34 Js e = 1.6 10 19 C o = 4 10 7 T mA 1 1 = 9 109 N m2 C 2 4 o me = 9.1 10 31 kg 1. 55/2/1 nmR>H$ go X a byn (nme) Ho$ Vb Ho$ A{^b ~dV {ZX{e V Mw ~H$s` jo _| {M _| Xem E AZwgma bMrbo Vma H$s A{Z`{_V AmH ${V, abcd H$mo aIZo na dh d mr` AmH$ma _| ~Xb OmVr h & Vma _| C n o[aV Ymam H$s {Xem H$m AZw_mZ bJmBE & 3 1 P.T.O. A flexible wire of irregular shape, abcd, as shown in the figure, turns into a circular shape when placed in a region of magnetic field which is directed normal to the plane of the loop away from the reader. Predict the direction of the induced current in the wire. 2. 3. {H$gr Amdo{eV MmbH$ Ho$ n R> Ho$ `oH$ {~ X na p Wa-d wV jo H$mo n R> Ho$ A{^b ~dV `m| hmoZm Mm{hE ? H$maU Xr{OE & 1 Why must electrostatic field at the surface of a charged conductor be normal to the surface at every point ? Give reason. EH$ Q>ogbm H$s n[a^mfm, {H$gr Mw ~H$s` jo B _| v doJ go J{V_mZ Amdoe q Ho$ H$U 1 na H$m` aV Mw ~H$s` ~b Ho$ {bE ` OH$ H$m Cn`moJ H$aVo h E, H$s{OE & Define one tesla using the expression for the magnetic force acting on a particle of charge q moving with velocity v in a magnetic field B . 4. j` VWm + j` XmoZm| hr {H $`mAm| _|, Zm{^H$ H$s `_mZ g `m g_mZ ahVr h O~{H$ j` _| na_mUw g `m Z _| EH$ H$s d { VWm + j` _|o EH$ H$s H$_r hmo OmVr h & H$maU g{hV `m `m H$s{OE & 1 In both and + decay processes, the mass number of a nucleus remains same whereas the atomic number Z increases by one in decay and decreases by one in + decay. Explain, giving reason. 5. {Z Z{b{IV {d wV -Mw ~H$s` V aJm| H$mo CZH$s Amd { m`m| Ho$ ~ T>Vo H $_ _| `dp WV H$s{OE -{H$aU|, gy _ Va J|, Ada $ {H$aU| Am a nam~ JZr {H$aU| & : Arrange the following electromagnetic waves in order of increasing frequency : -rays, microwaves, infrared rays and ultraviolet rays. 55/2/1 4 1 6. AmaoI _| {H$gr YZmdoe na jo aoImE Xem `r J`r h & {H$gr bKw YZmdoe H$mo Q go P VH$ J{V H$amZo _| jo mam {H$`m J`m H$m` YZm _H$ h AWdm G$Um _H$ ? H$maU Xr{OE & 1 Figure shows the field lines on a positive charge. Is the work done by the field in moving a small positive charge from Q to P positive or negative ? Give reason. 7. H$me-{d wV ^md _|, {H$gr H$me-gwJ mhr n R> na Amn{VV EH$dUu {d{H$aU H$s Vrd Vm _| d { hmoZo na H$me-{d wV Ymam _| d { `m| hmoZr Mm{hE ? `m `m H$s{OE & 1 In photoelectric effect, why should the photoelectric current increase as the intensity of monochromatic radiation incident on a photosensitive surface is increased ? Explain. 8. 55/2/1 {M _| Xem E AZwgma {H$gr nmaXeu Jmobo, {OgH$m Ho$ C h , na H$moB H$me {H$aU Amn{VV h & Jmobo go {ZJ V {H$aU aoIm AB Ho$ g_m Va h & `{X Jmobo Ho$ nXmW H$m AndV Zm H$ 3 h , Vmo {~ X A na AndV Z H$moU kmV H$s{OE & 5 1 P.T.O. A ray of light falls on a transparent sphere with centre C as shown in the figure. The ray emerges from the sphere parallel to the line AB. Find the angle of refraction at A if refractive index of the material of the sphere is 3. 9. Xmo A{V bKw gd g_ d mr` byn (nme), (1) Am a (2), {OZgo g_mZ YmamE I dm{hV hmo ahr h , {M _| Xem E AZwgma EH$-X gao Ho$ `m{_Vr` Ajmo H$mo b ~dV aIVo h E D$ dm Ya (H$m J O Ho$ Vb Ho$ gmnoj) aIo JE h & {~ X O na C n ZoQ> Mw ~H$s` jo H$m n[a_mU Am a {Xem kmV H$s{OE & Two very small identical circular loops, (1) and (2), carrying equal currents I are placed vertically (with respect to the plane of the paper) with their geometrical axes perpendicular to each other as shown in the figure. Find the magnitude and direction of the net magnetic field produced at the point O. 55/2/1 6 2 10. AmXe g Ym[a Ho$ `mdVu Ymam (ac) n[anW Ho$ {bE `h Xem BE {H$ n[anW _| dm{hV Ymam H$bm _| dmo Q>Vm go /2 AmJo ahVr h & 2 Show that the current leads the voltage in phase by /2 in an ac circuit containing an ideal capacitor. 11. 2 AZwMw ~H$s` nXmW Am a {VMw ~H$s` nXmW Ho$ ~rM {d^oXZ H$aZo dmbo Xmo {~ X {b{IE & Give two points to distinguish between a paramagnetic and a diamagnetic substance. 12. 2 Xem E JE n[anW _| g Ym[a na Amdoe kmV H$s{OE & Find the charge on the capacitor as shown in the circuit. 13. {M _| Xem E JE n[anW mam {Z ${nV Vw ` JoQ> H$mo nhMm{ZE & BgH$m VH $ VrH$ It{ME Am a g `_mZ gmaUr {b{IE & 2 Identify the equivalent gate represented by the circuit shown in the figure. Draw its logic symbol and write the truth table. 55/2/1 7 P.T.O. 14. AmaoI _| { _ go {H$gr H$me {H$aU H$mo Jw OaVo h E Xem `m J`m h & `{X And{V V {H$aU QR AmYma BC Ho$ g_m Va h , Vmo `h Xem BE {H$ (i) r1 = r2 = A/2, (ii) `yZV_ {dMbZ H$moU, Dm = 2i A. 2 Figure shows a ray of light passing through a prism. If the refracted ray QR is parallel to the base BC, show that (i) r1 = r2 = A/2, (ii) angle of minimum deviation, Dm = 2i A. 15. _mSw>bZ nX H$s n[a^mfm {b{IE & bm H$ AmaoI It{ME & AM {g Zb m H$aZo Ho$ {bE gab _mSw>bH$ H$m 2 Define the term modulation. Draw a block diagram of a simple modulator for obtaining AM signal. 16. (a) (b) (a) (b) 17. XmobZr Amdoe {H$g H$ma {d wV -Mw ~H$s` Va J| C n H$aVm h ? + z-{Xem Ho$ AZw{Xe g M[aV {H$gr {d wV -Mw ~H$s` Va J Ho$ Xmobr` {d wV Am a Mw ~H$s` jo m| H$mo Xem Zo dmbm `d Wm AmaoI It{ME & How does oscillating charge produce electromagnetic waves ? Sketch a schematic diagram depicting oscillating electric and magnetic fields of an em wave propagating along + z-direction. p- H$ma Ho$ AY MmbH$ Am a n- H$ma Ho$ AY MmbH$ Ho$ Vmn T > 0 K na D$Om ~ S> AmaoI It{ME & BZ AmaoIm| na, XmVm Am a J mhr D$Om Vam| H$mo CZH$s D$Om Am| g{hV A {H$V H$s{OE & AWdm D$Om ~ S> AmaoIm| Ho$ AmYma na {H$gr YmVw Am a {H$gr {d wV amoYr Ho$ ~rM {d^oXZ H$s{OE & 55/2/1 2 8 2 2 Draw energy band diagrams of an n-type and p-type semiconductor at temperature T > 0 K. Mark the donor and acceptor energy levels with their energies. OR Distinguish between a metal and an insulator on the basis of energy band diagrams. 18. {H$gr loUr~ LCR n[anW _|, dh p W{V`m m H$s{OE {OZ_| (i) n[anW H$s {V~mYm `yZV_ hmoVr h , Am a (ii) n[anW _| dmQ>hrZ Ymam dm{hV hmoVr h & 2 In a series LCR circuit, obtain the conditions under which (i) the impedance of the circuit is minimum, and (ii) wattless current flows in the circuit. 19. Xmo Hw$ S>{b`m|, {OZHo$ d oaH$ d L1 = 16 mH Am a L2 = 12 mH h , go dm{hV {d wV YmamAm| _| g_mZ Xa go d { hmo ahr h & `{X XmoZm| Hw$ S>{b`m| H$mo XmZ H$s OmZo dmbr e{ $ g_mZ h , Vmo {H$gr {XE JE jU na BZ XmoZm| Hw$ S>{b`m| _| (i) o[aV dmo Q>VmAm|, (ii) YmamAm| Am a (iii) g {MV D$Om Am| H$m AZwnmV kmV H$s{OE & 3 The currents flowing in the two coils of self-inductance L1 = 16 mH and L2 = 12 mH are increasing at the same rate. If the power supplied to the two coils are equal, find the ratio of (i) induced voltages, (ii) the currents and (iii) the energies stored in the two coils at a given instant. 20. H$moB {~ X {H$V Amdoe (+Q) {H$gr AZmdo{eV YmVw H$s MmXa Ho$ g_rn p WV h & Amdoe Am a YmVw H$s MmXa Ho$ ~rM {d wV -jo aoImE It{ME & (b) 55/2/1 (a) Xmo nVbo g_m Va AZ V Vb erQ> {OZHo$ Amdoe KZ d 1 VWm 2 ( 1 > 2) h , {M _| Xem E JE h & II Am a III mam A {H$V jo m| _| ZoQ> {d wV -jo m| Ho$ n[a_mU Am a {XemE {b{IE & 9 3 P.T.O. (a) A point charge (+Q) is kept in the vicinity of uncharged conducting plate. Sketch electric field lines between the charge and the plate. (b) Two infinitely large plane thin parallel sheets having surface charge densities 1 and 2 ( 1 > 2) are shown in the figure. Write the magnitudes and directions of the net fields in the regions marked II and III. 21. (a) (b) Xmo b ~o grYo g_m Va MmbH$m| a Am a b , {OZ_| Wm`r YmamE Ia Am a Ib dm{hV hmo ahr h , Ho$ ~rM n WH$Z X ar d h & MmbH$ a mam MmbH$ b Ho$ AZw{Xe {~ X Am| na C n Mw ~H$s` jo H$m n[a_mU Am a {Xem {b{IE & `{X BZ MmbH$m| _| dm{hV YmamAm| H$s {Xem g_mZ h , Vmo XmoZm| MmbH$m| Ho$ ~rM ~b H$m n[a_mU Am a H ${V `m h ? AmaoI H$s ghm`Vm go Xem BE {H$ O~ BZ MmbH$m| go YmamE {dnarV {XemAm| _| dm{hV hmoVr h , Vmo XmoZmo MmbH$mo Ho$ ~rM ~b _| {H$g H$ma n[adV Z hmoJm & (a) 22. Two long straight parallel conductors a and b , carrying steady currents Ia and Ib are separated by a distance d. Write the magnitude and direction of the magnetic field produced by the conductor a at the points along the conductor b . If the currents are flowing in the same direction, what is the nature and magnitude of the force between the two conductors ? (b) Show with the help of a diagram how the force between the two conductors would change when the currents in them flow in the opposite directions. C{MV AmaoIm o H$s ghm`Vm go g MaU H$s (i) AmH$me Va J Am a (ii) `mo_ Va J {d{Y`m| H$m g jon _| dU Z H$s{OE & g MaU H$s BZ {d{Y`m| _| `w $ Va Jm| H$s Amd { m`m| Ho$ n[aga H$m C oI ^r H$s{OE & Describe briefly, by drawing suitable diagrams, the (i) sky wave and (ii) space wave modes of propagation. Mention the frequency range of the waves in these modes of propagation. 55/2/1 3 10 3 23. (a) (b) (a) (b) 24. g jon _| dU Z H$s{OE {H$ {H$g H$ma S>o{dgZ VWm O_ a `moJ mam Bbo Q >m Zm| H$s Va J H ${V H$m {ZXe Z {H$`m J`m & {H$gr Bbo Q >m Z H$mo CgH$s {dam_md Wm go {H$gr {d^d V mam d[aV {H$`m OmVm h & Bggo g ~ Xo-~ m br Va JX ` Ho$ {bE ` OH$ m H$s{OE & 3 Describe briefly how Davisson Germer experiment demonstrated the wave nature of electrons. An electron is accelerated from rest through a potential V. Obtain the expression for the de-Broglie wavelength associated with it. H$jm X H$s N>m m nyOm Zo AnZr _mVmOr H$mo Iwbo _| H$n S>o YmoVo g_`, gm~wZ Ho$ a JrZ ~wb~wbo XoIo Am a Cgo `h OmZZo H$s {Okmgm h B {H$ gm~wZ Ho$ ~wb~wbo a JrZ `m| VrV hmoVo h & gm` H$mb O~ CgHo$ {nVmOr, Omo noeo go B Or{Z`a h , Ka AmE Vmo CgZo Bgr {df` _| CZgo Z nyN>m & CgHo$ {nVmOr Zo Cgo ^m {VH$s H$s Cg _yb n[aKQ>Zm go AdJV H$am`m {OgHo$ H$maU gm~wZ Ho$ ~wb~wbo a JrZ {XImB XoVo h & (a) AmnHo$ {dMma go nyOm Am a CgHo$ {nVmOr {H$Z _y `m| H$mo Xem Vo h ? (b) gm~wZ Ho$ a JrZ ~wb~wbo ~ZZo _| gp _{bV H$m{eH$ n[aKQ>Zm H$m C oI H$s{OE & 3 When Puja, a student of 10th class, watched her mother washing clothes in the open, she observed coloured soap bubbles and was curious to know why the soap bubbles appear coloured. In the evening when her father, an engineer by profession, came home, she asked him this question. Her father explained to her the basic phenomenon of physics due to which the soap bubbles appear coloured. (a) (b) 25. What according to you are the values displayed by Puja and her father ? State the phenomenon of light involved in the formation of coloured soap bubbles. (a) OoZa S>m`moS> H$m g {daMZ ({Z_m U) g {Y Ho$ p- VWm n- XmoZm| \$bH$mo H$mo A `{YH$ An{_{lV H$aHo$ `m| {H$`m OmVm h ? dmo Q>Vm {Z` H$ Ho$ $n _| OoZa S>m`moS> Ho$ Cn`moJ H$mo Xem Zo Ho$ {bE n[anW AmaoI ItMH$a g jon _| BgH$s H$m` {d{Y H$s `m `m H$s{OE & AWdm (b) (a) (b) 55/2/1 \$moQ>moS>m`moS> H$m {Z_m U {H$g H$ma {H$`m OmVm h ? BgH$s H$m` {d{Y H$m g jon _| dU Z H$s{OE & Xmo {d{^ XrnZ-Vrd VmAm| Ho$ {bE BgHo$ V I A{^bmj{UH$ It{ME & 11 3 3 P.T.O. (a) (b) Why is zener diode fabricated by heavily doping both p- and n-sides of the junction ? Draw the circuit diagram of zener diode as a voltage regulator and briefly explain its working. OR (a) How is a photodiode fabricated ? (b) Briefly explain its working. Draw its V I characteristics for two different intensities of illumination. 26. (i) (ii) (iii) AY w{dV H$me Am a a {IH$V: Y w{dV H$me Ho$ ~rM {d^oXZ H$s{OE & nmoboam BS> {H$g H$ma ~Zm`m OmVm h ? `h a {IH$V: Yw {dV H$me {H$g H$ma C n H$aVm h ? g jon _| `m `m H$s{OE {H$$ dm`w_ S>br` H$Um| go H$s{U V hmoH$a gy` H$m H$me {H$g H$ma Y w{dV hmo OmVm h & (i) (ii) 27. Distinguish between unpolarised and linearly polarised light. What does a polaroid consist of ? How does it produce a linearly polarised light ? (iii) Explain briefly how sunlight is polarised by scattering through atmospheric particles. {H$gr g_m Va n{ >H$m g Ym[a _|, {OgH$s n{ >H$mAm| Ho$ ~rM dm`w h , H$s `oH$ n{ >H$m H$m jo \$b 6 10 3 m2 Am a n{ >H$mAm| Ho$ ~rM n WH$Z 3 mm h & (i) Bg g Ym[a H$s Ym[aVm n[aH${bV H$s{OE & (ii) `{X Bg g Ym[a H$mo 100 V Amny{V go g `mo{OV {H$`m OmE, Vmo `oH$ n{ >H$m na {H$VZm Amdoe hmoJm ? (iii) `{X dmo Q>Vm Amny{V H$mo g `mo{OV aIVo h E g Ym[a H$s n{ >H$mAm| Ho$ ~rM K = 6 H$s A^ H$ H$s 3 mm _moQ>r MmXa aI Xr OmE, Vmo n{ >H$mAm| na Amdoe {H$g H$ma ^m{dV hmoJm ? In a parallel plate capacitor with air between the plates, each plate has an area of 6 10 3 m2 and the separation between the plates is 3 mm. (i) (ii) (iii) 55/2/1 3 Calculate the capacitance of the capacitor. If this capacitor is connected to 100 V supply, what would be the charge on each plate ? How would charge on the plates be affected, if a 3 mm thick mica sheet of K = 6 is inserted between the plates while the voltage supply remains connected ? 12 3 28. (a) ~moa Ho$ A{^J hrVm| H$m Cn`moJ H$aHo$, hmBS >moOZ na_mUw H$s p Wa Ad WmAm| _| Bbo Q >m Z H$s Hw$b D$Om Ho$ {bE ` OH$ `w n H$s{OE & (b) [aS>~J gy H$m Cn`moJ H$aHo$, bmB_oZ loUr Am a ~m_a loUr Ho$ nhbo gX ` H$s no Q >_r aoImAm| H$s Va JX `m o H$mo n[aH${bV H$s{OE & 5 AWdm (a) (i) AY -Am`w j` p Wam H$ (b) (a) (T1/2) ( ) go Am a (ii) Am gV Am`w ( ) nXm| H$s n[a^mfm {b{IE & BZHo$ g ~ Y kmV H$s{OE & {H$gr ao{S>`moEop Q>d Zm{^H$ H$m j` p Wam H$ = 0.3465 ({XZ) 1 h & Amap ^H$ _m m go 75% VH$ j{`V hmoZo _| BgHo$ Zm{^H$ H$mo {H$VZm g_` bJoJm ? 5 Using Bohr s postulates, derive the expression for the total energy of the electron in the stationary states of the hydrogen atom. (b) Using Rydberg formula, calculate the wavelengths of the spectral lines of the first member of the Lyman series and of the Balmer series. OR (a) Define the terms (i) half-life (T1/2) and (ii) average life ( ). Find out their relationships with the decay constant ( ). (b) 29. 55/2/1 A radioactive nucleus has a decay constant = 0.3465 (day) 1. How long would it take the nucleus to decay to 75% of its initial amount ? (a) {d^d_mnr H$m {g m V {b{IE & {d^d dUVm H$s n[a^mfm {b{IE & {d^d_mnr Vma H$s {VamoYH$Vm Ho$ nXm| _| {d^d dUVm Ho$ {bE ` OH$ m H$s{OE & 13 P.T.O. (b) {M _| {Z`V {d^d dUVm H$m H$moB b ~m {d^d_mnr Vma AB Xem `m J`m h & 1 VWm 2 {d wV -dmhH$ ~bm| Ho$ Xmo mW{_H$ gobm|, {O h| Xem E AZwgma g `mo{OV {H$`m J`m h , Ho$ {bE ey ` {djon p W{V`m , {gao A go X [a`m| l1 = 120 cm VWm l2 = 300 cm na m hmoVr h & (i) 1/ 2 Am a (ii) Ho$db 1 gob Ho$ {bE ey ` {djon p W{V kmV H$s{OE & 5 AWdm (a) (b) (a) 55/2/1 {H$gr MmbH$ _| Amdoe dmhH$m| Ho$ Andmh doJ nX H$s n[a^mfm {b{IE & {dlm {V H$mb Ho$ nXm| _| Ymam KZ d Ho$ {bE ` OH$ m H$s{OE & 100 V H$s H$moB ~ Q>ar Xem E JE {d wV ZoQ>dH $ _| g `mo{OV h & `{X 2 {VamoYH$ _| Cn^w $ e{ $ 200 W h , Vmo 5 {VamoYH$ _|o e{ $-j` {ZYm [aV H$s{OE & State the principle of a potentiometer. Define potential gradient. Obtain an expression for potential gradient in terms of resistivity of the potentiometer wire. 14 5 (b) Figure shows a long potentiometer wire AB having a constant potential gradient. The null points for the two primary cells of emfs 1 and 2 connected in the manner shown are obtained at a distance of l1 = 120 cm and l2 = 300 cm from the end A. Determine (i) 1/ 2 and (ii) position of null point for the cell 1 only. OR (a) (b) 55/2/1 Define the term drift velocity of charge carriers in a conductor. Obtain the expression for the current density in terms of relaxation time. A 100 V battery is connected to the electric network as shown. If the power consumed in the 2 resistor is 200 W, determine the power dissipated in the 5 resistor. 15 P.T.O. 30. (a) (b) (a) (b) {H$gr X a W {~ ~ H$m {V{~ ~ ~ZZm Xem Zo Ho$ {bE IJmobr` X aXe H$ H$m Zm_m {H$V {H$aU AmaoI It{ME & {H$gr X aXe H$ H$s C AmdY Z j_Vm Am a C {d^oXZ j_Vm Ho$ {bE A{^ `H$ VWm Zo{ H$m b|gm| H$m M`Z H$aVo g_` Amd `H$ `mZ XoZo `mo ` _wI {dMmam| H$m C oI H$s{OE & {H$gr g `w $ gy _Xeu Ho$ A{^ `H$ H$s \$moH$g X ar 1.25 cm Am a Zo{ H$m H$s \$moH$g X ar 5 cm h & H$moB bKw {~ ~ BgHo$ A{^ `H$ go 2.5 cm X ar na aIm J`m h & `{X Ap V_ {V{~ ~ AZ V na ~ZVm h , Vmo A{^ `H$ Am a Zo{ H$m Ho$ ~rM H$s X ar kmV H$s{OE & AWdm ` J Ho$ { -{Par `moJ _| m `{VH$aU { \ $ Om| Am a nVbr EH$b {Par Ho$ H$maU m {ddV Z n Q>Z Ho$ ~rM {d^oXZ H$aZo `mo ` VrZ A{^bmj{UH$ {deofVmE {b{IE & 500 nm Va JX ` H$m H$moB g_m Va H$me nw O {H$gr nVbr {Par na AmnVZ H$aVm h Am a n[aUm_r {ddV Z n Q>Z 1 m X ar na p WV nX o na {XImB XoVm h & ojU H$aZo na `h nm`m OmVm h {H$ W_ {Zp Z R> Ho$ go 2.5 mm H$s X ar na h & {Par H$s Mm S>mB kmV H$s{OE & (a) Draw a labelled ray diagram of an astronomical telescope to show the image formation of a distant object. Write the main considerations required in selecting the objective and eyepiece lenses in order to have large magnifying power and high resolution of the telescope. (b) A compound microscope has an objective of focal length 1.25 cm and eyepiece of focal length 5 cm. A small object is kept at 2 .5 cm from the objective. If the final image formed is at infinity, find the distance between the objective and the eyepiece. OR (a) (b) 55/2/1 Write three characteristic features to distinguish between the interference fringes in Young s double slit experiment and the diffraction pattern obtained due to a narrow single slit. A parallel beam of light of wavelength 500 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1 m away. It is observed that the first minimum is a distance of 2.5 mm away from the centre. Find the width of the slit. 16 5 5

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