TOPPER SAMPLE PAPER 2 Class XII- Physics

Transcription

1 TOPPER SAMPLE PAPER 2 Class XII- Physics Time: Three Hurs Maximum Marks: 70 General Instructins (a) All questins are cmpulsry. (b) There are 30 questins in ttal. Questins 1 t 8 carry ne mark each, questins 9 t 18 carry tw marks each, questins 19 t 27 carry three marks each and questins 28 t 30 carry five marks each. (c) There is n verall chice. Hwever, an internal chice has been prvided in ne questin f tw marks, ne questin f three marks and all three questins f five marks each. Yu have t attempt nly ne f the given chices in such questins. (d) Use f calculatins is nt permitted. (e) Yu may use the fllwing physical cnstants wherever necessary. 19 e = C c = 3 10 ms h = Js µ = 4λ 10 TmA kb = JK 23 NA = / mle 27 mn = kg 1. In spite f having magnitude as well as directin the current is a scalar quantity. Why? (1) 2. Give the directin in which induced current flws in the wire lp, when the magnet mves twards the lp as shwn belw.

2 (1) 3. Hw is the current represented mathematically in frward bias? (1) 4. What is the rati f speed f infrared rays and ultravilet rays in vacuum? (1) 5. Hw will the size f an bject appear changed when viewed by a telescpe having fcal length f the bjective and eyepiece as 60 cm and 5 cm respectively? (1) 6. Find the rati f nuclear densities f the tw nuclei having mass numbers in the rati 1 : 4? (1) 7. A. C. pwer is transmitted frm ne statin t anther at highest pssible vltage. Why? (1) 8. Why d semicnductr devices nt wrk at abslute zer temperature? (1) 9. An electric diple with diple mment directin f a unifrm electric field f magnitude magnitude f the trque acting n the diple. (2) C-m is aligned at 30 with the NC Calculate the 10. What is the change in resistance f a wire when its radius is halved and the length is reduced t ne furth f its riginal value? (2) 11. In Yung s duble slit experiment the size f slits is taken f the rder f the wavelength f the light used in the experiment. Give reasn fr it. (2) 12. Why are ferrmagnetic materials used in memry devices? (2) 13. Find the wavelength f electrmagnetic waves f frequency 6 x Hz in free space. Give the tw applicatins f this wave. (2) 14. A cnvex lens f refractive index 1.5 has a fcal length f 18 cm in air. Calculate the change in its fcal length when it is immersed in water f refractive index f 4/3. (2) 15. The given graph shws the variatin f charge q versus ptential difference V fr capacitrs C 1 andc 2. The tw capacitrs have same plate separatin. But the plate area fc 2 is duble than that f C 1. Which f the lines in the graph crrespnd t C1 andc2 and why?

3 16. Explain hw the maximum kinetic energy f the electrns emitted frm a metal surface vary with the frequency f incident radiatin. (2) Draw a graph shwing the variatin f stpping ptential with frequency f incident radiatin in relatin t pht electric effect. Deduce an expressin fr the slpe f this graph using Einstein s phtelectric equatin. (2) 17. The half life f 14 6C is 5700 years. What des it mean? Tw radiactive nuclei x and y initially cntain n equal number f atms. Their half lives are 1 hur and 2 hur respectively. Calculate the rati f their rates f disintegratin after tw hurs. (2) 18. Distinguish between frequency mdulatin and amplitude mdulatin. (2) 19. S 1 and S 2 are tw hllw cncentric spheres enclsing charges Q and 2Q respectively. i. What is rati f the electric flux thrugh S 1 and S 2? ii.hw will the electric flux thrugh the sphere S 1 change, if a medium f dielectric cnstant 5 is intrduced in the space inside S 1 in place f air? (3) 20. Tw dielectric slabs f dielectric cnstants K 1 and K 2 and f equal width are filled in between the tw plates, each f area A f the parallel plate capacitr. Hw des the capacitance f the capacitr get affected? (3) 21. A pint charge +10µC is at a distance 5 cm directly abve the center f a square f side 10 cm as shwn in figure.

4 22. What is the magnitude f the electric flux thrugh the square? A parallel plate capacitr with air as dielectric is charged by a d. c. surce t a ptential V. Withut discnnecting the capacitr frm the surce, air is replaced by anther dielectric medium f dielectric cnstant 10. Hw des electric field between the plates and energy stred in the capacitr change? (3) 23. A ray f light which mves frm denser t rarer medium underges ttal internal reflectin. Derive the expressin fr critical angle in terms f speed f light in the respective media. (3) 24. State the cnditin under which the phenmenn f resnance ccurs in a series LCR circuit. Plt a graph shwing variatin f current with frequency f a.c. surce in a series LCR circuit. (3) 25. Tw cherent surces whse intensity rati is 81:1 prduce interference fringes. Find the rati f intensity f maxima and minima in fringe system. (3) 26. A lng slenid with 15 turns per cm has a small lp f area 2.0 cm 2 placed inside nrmal t the axis f the slenid. If the current carried by the slenid changes steadily frm 2A t 4A in 0.1 sec, what is the induced emf in the lp while the current is changing? (3) 27. Hw des the size f a nucleus depend n its mass number? Explain why the density f nuclear matter is independent f the size f nucleus. (3) 28. Give the frequency ranges f the fllwing: (i) High frequency band (HF) (ii) Ultra high frequency band (UHF) (iii) Super high frequency band (SHF) (3) 29. Using Ampere s circuital law, derive an expressin fr the magnetic field alng the axis f a tridal slenid.

5 Derive an expressin fr the trque n a rectangular cil f area A carrying current I placed in a magnetic field B at an angle θ t the directin f the field. (5) 30. Derive lens maker s frmula fr a duble cnvex lens. Draw a ray diagram f a cmpund micrscpe shwing the final image frmatin at least distance f distinct visin D. State its wrking principle. Shw that its magnifying pwer is given as M v D 1 1 u Fe ve = The circuit symbl f a lgic gate and tw input wavefrms A and B are shwn in the figure given belw. (5) i) name the lgic gate ii) write its truth table iii) Tabulate the details f utput wavefrm & represent its utput wavefrm graphically. With the help f a labeled circuit diagram, describe wrking principle f a cmmn emitter amplifier using a p n p transistr. Define the terms current gain and vltage gain and write their expressins. (5)