CBSE PREVIOUS YEAR QUESTION PAPER CLASS XII

Transcription

1 CBSE PREVIOUS YEAR QUESTION PAPER CLASS XII PHYSICS (Theory) Rias fail, {"1c0-1Paas) 1

2 âæ æ Ø çùùùüàæ Ù (i) âöè ÂýàÙ çùßæøü ãñ Ð ÂýàÙ- æ ð é 26 ÂýàÙ ãñ Ð ÂýàÙ- æ ð 5 Öæ» ãñ ¹ ÇU, ¹ ÇU Õ, ¹ ÇU, ¹ ÇU Î æñúu ¹ ÇU ØÐ (iii) ¹ ÇU ð 5 ÂýàÙ ãñ, ÂýˆØð æ 1 ãñð ¹ ÇU Õ ð 5 ÂýàÙ ãñ, ÂýˆØð ð 2 ãñ Ð ¹ ÇU â ð 12 ÂýàÙ ãñ, ÂýˆØð ð ãñ Ð ¹ ÇU Î ð 4 æ êëøæïæçúuì ÂýàÙ ãñ æñúu ¹ ÇU Ø ð ÂýàÙ ãñ, ÂýˆØð ð 5 ãñ Ð (iv) (v) ÂýàÙ- æ ð â»ý ÂÚU æð ü çß Ë Ùãè ãñð ÌÍæçÂ, Îæð æð ßæÜð ÂýàÙ ð, ÌèÙ æð ßæÜð ÂýàÙ ð æñúu Âæ æð ßæÜð ÌèÙæð ÂýàÙæð ð æ ÌçÚU ØÙ ÂýÎæÙ ç Øæ»Øæ ãñð ðâð ÂýàÙæð ð æâ æð çî» ØÙ ð âð ð ßÜ ÂýàÙ ãè ÚUÙæ ãñð Áãæ æßàø ãæð æâ çù ÙçÜç¹Ì ÖæñçÌ çùøìæ æð ð æùæð æ ÂØæð» ÚU â Ìð ãñ Ñ c510 8 m/s h Js e C m 0 54p10 27 T m A 21 e C 2 N 21 m p ε N m C Üð ÅþUæòÙ æ ÎýÃØ æù kg ØêÅþUæòÙ æ ÎýÃØ æù kg ÂýæðÅUæòÙ æ ÎýÃØ æù kg æßæð»æîýæð â Øæ ÂýçÌ»ýæ æðü ÕæðËÅ U$Á æù çùøìæ JK 21 2

3 General Instructions : (i) (iii) (iv) (v) All questions are compulsory. There are 26 questions in all. This question paper has five sections : Section A, Section B, Section C, Section D and Section E. 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. 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. You may use the following values of physical constants wherever necessary. c510 8 m/s h Js e C m 0 54p10 27 T m A 21 e C 2 N 21 m p ε N m C Mass of electron kg Mass of neutron kg Mass of proton kg Avogadro s number per gram mole Boltzmann constant JK 21

4 ¹ ÇU - SECTION - A 1. ç æ Øæ r ð ç âè æâ, çáâ ð ð Îý ÂÚU æð ü Ø æßðàæ q çsíì ãñ, ð æúuæð æðúu ç âè æßðàæ Q æð»çì ÚUæÙð ð ç ÌÙæ æøü ç Øæ ÁæÌæ ãñ? 1 What is the amount of work done in moving a point charge Q around a circular arc of radius r at the centre of which another point charge q is located? 2. ç âè æßðàæ ßæã è»çìàæèüìæ è ÂçÚUÖæáæ çüç¹ Ð â æ çßÿææ çì æü âð Øæ â Õ Ï ãñ? 1 Define mobility of a charge carrier. What is its relation with relaxation time?. æßðçàæì æ è é ÇUçÜÙè»çÌ æ Øæ æúu æ ãæð â Ìæ ãñ? What can be the cause of helical motion of a charged particle? 1 4. é ãúðu âð ãæð ÚU ã SÂcÅU Øæð Ùãè Îð¹ ÂæÌð? â ð çü žæúuîæøè ÂçÚUƒæÅUÙæ æ Ùæ çüç¹ Ð 1 Why can t we see clearly through fog? Name the phenomenon responsible for it MHz æßëçžæ è ç âè ßæã ÌÚ U» ÂÚU æð ü 5 khz æßëçžæ æ çâ ÙÜ æøæ æòçéuçüì ãñð ˆÂóæ Âæàßü Õñ ÇUæð è æßëçžæøæ Øæ ãñ? 1 A signal of 5 khz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. What are the frequencies of the side bands produced? 4

5 ¹ ÇU - Õ SECTION - B 6. ÁÕ ç âè 0.1 m Ü Õð ÌæÚU ð çâúuæð ÂÚU 5V çßößæ ÌÚU Ü»æØæ ÁæÌæ ãñ, Ìæð Üð ÅþUæòÙæð è Âßæã æü m/s ãæðìè ãñð ØçÎ ÌæÚU ð Üð ÅþUæòÙ ƒæùˆß m 2 ãñ, Ìæð ÌæÚU ð ÂÎæÍü è ÂýçÌÚUæðÏ Ìæ ÂçÚU çüì èçá Ð When 5V potential difference is applied across a wire of length 0.1 m, the drift speed of electrons is m/s. If the electron density in the wire is m 2, calculate the resistivity of the material of wire ç âè ÂýæðÅUæòÙ ÌÍæ a- æ æð â æù çßößæ ÌÚU âð ˆßçÚUÌ ç Øæ»Øæ ãñð Ù ð âð ç â è (i) Îð Õýæò Üè ÌÚ U»ÎñƒØü çï, æñúu»çìá ª Áæü ãñ? ÂÙð žæúu è ÂéçcÅU èçá Ð A proton and an a particle are accelerated through the same potential difference. Which one of the two has (i) greater de-broglie wavelength, and less kinetic energy? Justify your answer ãæ ÇþUæðÁÙ ÂÚU æ æé ð ˆâÁüÙ SÂð ÅþU ð H a -ÚðU¹æ Õ ÂýæŒÌ ãæðìè ãñ? â â ý æ ð ˆâçÁüÌ È æðåuæòù è æßëçžæ ÂçÚU çüì èçá Ð Íßæ ãæ ÇþUæðÁÙ ÂÚU æ æé ð ÁÕ Üð ÅþUæòÙ n5: âð n51 ÂÚU ê ÎæÙ ÚUÌæ ãñ, ÌÕ ˆâçÁüÌ çßç ÚU ææð è ÌÚ U»ÎñƒØü ÂçÚU çüì èçá Ð When is H a line in the emission spectrum of hydrogen atom obtained? Calculate the frequency of the photon emitted during this transition. OR Calculate the wavelength of radiation emitted when electron in a hydrogen atom jumps from n5: to n æïæúu Õñ ÇU çâ ÙÜ æð âèïð ãè ÂýðçáÌ Øæð Ùãè ç Øæ ÁæÌæ? æð ü Îæð æúu æ çüç¹ Ð Why is base band signal not transmitted directly? Give any two reasons. 2 5

6 10. æúðu¹ ð Îàææü ÙéâæÚU æð ü ç ÚU æ PQ çâý BAC ð ÂßÌèü È Ü BA ÂÚU æâçìì ãæð ÚU â ð Ø ÂßÌèü È Ü AC âð RS ð M  ð â Âý æúu çù»üì ãæðìè ãñ, ç AQ5AR ãæðð ØçÎ çâý æð æ A5608 ÌÍæ çâý ð ÂÎæÍü æ ÂßÌüÙæ ãñ, Ìæð æð æ u ÂçÚU çüì èçá Ð 2 A ray PQ incident on the refracting face BA is refracted in the prism BAC as shown in the figure and emerges from the other refracting face AC as RS such that AQ5AR. If the angle of prism A5608 and refractive index of material of prism is, calculate angle u. ¹ ÇU - â SECTION - C 11. ç âè â æù æßðçàæì»æðüèø ¹æðÜ ð æúu æ (i) ¹æðÜ ð ÕæãÚU ÌÍæ ¹æðÜ ð ÖèÌÚU ç âè çõ Îé ÂÚU çßléì ÿæð æ ÌèßýÌæ ææì èçá Ð ¹æðÜ ð ð Îý âð ÎêÚUè æñúu çßléì ÿæð æ ð Õè»ýæÈ ¹è ç Ð Find the electric field intensity due to a uniformly charged spherical shell at a point (i) outside the shell and inside the shell. Plot the graph of electric field with distance from the centre of the shell. 6

7 V emf ð Îæð âßüâ âðüæð æð Âæàßü ð â ØæðçÁÌ ÚU ð Âæàßü ð â ØæðçÁÌ 7 V ð Îæð ÂýçÌÚUæðÏ æð ð Õæs ÂçÚUÂÍ æð çßléì è æâêçìü è»øè ãñð çì æ ÂýçÌÚUæðÏ ð ç âè ßæðËÅU èåuúu âð Ù âðüæð è ÅUç üùü ßæðËÅUÌæ 1.4 V æâè ÁæÌè ãñð ÂýˆØð âðü æ æ ÌçÚU ÂýçÌÚUæðÏ ÂçÚU çüì èçá Ð Two identical cells of emf 1.5 V each joined in parallel supply energy to an external circuit consisting of two resistances of 7 V each joined in parallel. A very high resistance voltmeter reads the terminal voltage of cells to be 1.4 V. Calculate the internal resistance of each cell. 1. ç ÂØÚU æ ÂçÚUÂÍèØ çùø çüç¹ Ð â çùø æ ÂØæð» ÚU ð âèïð Ù Ì çßléì ßæãè æü æ é Õ èø ÿæð æ ææì èçá Ð é Õ èø ÿæð æ ÚðU¹æ çsíúu çßléì ÿæð æ ÚðU¹æ æð âð ç â Âý æúu çöóæ ãæðìè ãñ? Íßæ âæ ÜæðÅþUæòÙ æ çâhæ Ì çüç¹ Ð Øã Îàææü ç âæ ÜæðÅþUæòÙ ð ææð æ ÂçÚU ý æ- æü Ù è æüæð ÂÚU çùöüúu Ùãè ÚUÌæÐ âæ ÜæðÅþUæòÙ ð Âý æüù ð çü Øã»é æ æßàø Øæð ãñ? State Ampere s circuital law. Use this law to find magnetic field due to straight infinite current carrying wire. How are the magnetic field lines different from the electrostatic field lines? OR State the principle of a cyclotron. Show that the time period of revolution of particles in a cyclotron is independent of their speeds. Why is this property necessary for the operation of a cyclotron? 14. (i) ÁÕ ç âè AC dæðì æð ç âè æîàæü â ÏæçÚU æ âð â ØæðçÁÌ ç Øæ ÁæÌæ, Ìæð Øã Îàææü ç ÂêÚðU ý ð dæðì mæúuæ æâêìü æñâì àæç Ì àæê Ø ãæðìè ãñð æð ü ÕËÕ ç âè ÂçÚUßÌèü â ÏæçÚU æ âð A.C. dæðì âð Ÿæð æè ý ð â ØæðçÁÌ ãñð â ÕËÕ è æð Øæ ãæðìæ ãñ ÁÕ ÂçÚUÂÍ ð ŒÜ» Ü»æ çîøæ ÁæÌæ ãñ æñúu â ÏæçÚU æ è ÏæçÚUÌæ æð ÏèÚðU-ÏèÚðU ƒæåuæøæ ÁæÌæ ãñ? 7

8 (i) When an AC source is connected to an ideal capacitor, show that the average power supplied by the source over a complete cycle is zero. A bulb is connected in series with a variable capacitor and an A.C. source as shown. What happens to the brightness of the bulb when the key is plugged in and capacitance of the capacitor is gradually reduced? 15. çßléì é Õ èø ÌÚ U» ð ç â Âý æúu ˆÂóæ ãæðìè ãñ? Ù ÌÚ U»æð è ª Áæü æ dæðì Øæ ãæðìæ ãñ? z- ÿæ ð ÙéçÎàæ â ÚU æ ÚUÙð ßæÜè ç âè çßléì - é Õ èø ÌÚ U» ð çßléì ß é Õ èø ÿæð ææð ð çü»ç æìèø ÃØ ÁÙ çüç¹ Ð çßléì é Õ èø ÌÚ U»æð ð æð ü Îæð»é æ çüç¹ Ð How are electromagnetic waves produced? What is the source of energy of these waves? Write mathematical expressions for electric and magnetic fields of an electromagnetic wave propagating along the z-axis. Write any two important properties of electromagnetic waves. 16. (i) Âý æàæ ð âƒæù æšø âð çßúuü æšø ð» Ù ÚUÙð ð Âý ÚU æ ð ãæ»ð â ð ÌÚ U» çâhæ Ì ð æïæúu ÂÚU SÙðÜ æ çùø ÃØéˆÂóæ èçá Ð â ÌÜ ÌÚ U»æ»ý æñúu»æðüèø ÌÚ U»æ»ý ð Õè çßöðîù ÚUÙð ð çü æúðu¹ ¹è ç Ð (i) Derive Snell s law on the basis of Huygen s wave theory when light is travelling from a denser to a rarer medium. Draw the sketches to differentiate between plane wavefront and spherical wavefront. 17. æ SÅUèÙ è Âý æàæ-çßléì â è ÚU æ çü¹ùð ð ÂØæð» ãæðùð ßæÜð È æðåuæòùæð ð Îæð ãˆßâê æü»é ææð æ ËÜð¹ èçá Ð æ SÅUèÙ è â è ÚU æ æ ÂØæð» ÚU ð ÌÍæ Âýæâ ç» ÚUæçàæØæð ð Õè æßàø»ýæè ¹è ÚU (i) çùúuæðïè çßöß, æñúu ÎðãÜè æßëçžæ è ÂçÚUÖæáæ çüç¹ Ð State two important properties of photon which are used to write Einstein s photoelectric equation. Define (i) stopping potential and threshold frequency, using Einstein s equation and drawing necessary plot between relevant quantities. 8

9 18. (i) Ù Îæð ãˆßâê æü Âýç ý Øæ æð æ Ùæ çüç¹ Áæð pn â çï ÕÙÌð â Ø ãæðìè ãñ Ð Âê æü ÌÚ U» çîcåu æúuè æ çßléì ÂçÚUÂÍ çùßðàæè æñúu çù»üì ÌÚ U» M Âæð âçãì ¹è ç Ð â ÿæðâ ð ÃØæ Øæ èçá ç çù»üì ßæðËÅUÌæ/ÏæÚUæ ç â Âý æúu çîçàæ ãæðìè ãñð (i) Name two important processes that occur during the formation of a pn junction. Draw the circuit diagram of a full wave rectifier along with the input and output waveforms. Briefly explain how the output voltage/current is unidirectional. 19. (i) ª Áæü Õñ ÇU æúðu¹ ð æïæúu ÂÚU ç âè æü æñúu Ïü æü ð Õè çßöðîù èçá Ð Ùè ð çî» æúðu¹ ð ç âè»ðåu ð çùßðàæè ÌÚ U» M  (A, B) ÌÍæ çù»üì ÌÚ U» M  (Y) Îàææü» ãñ Ð â»ðåu æð Âã æçù, â è âˆø æù âæúu æè çüç¹ æñúu Ì ü ÂýÌè ¹è ç Ð 9

10 (i) Distinguish between a conductor and a semi conductor on the basis of energy band diagram. The following figure shows the input waveforms (A, B) and the output waveform (Y) of a gate. Identify the gate, write its truth table and draw its logic symbol. 20. æ æàæ ÌÚ U»æð mæúuæ ÂýâæÚU æ Øæ ãñ? Ù æúu æð æ ËÜð¹ èçá Áæð Ù ð ÂýâæÚU æ ð ÂçÚUâÚU æð âèç Ì ÚUÌð ãñ Ð æ æàæ ÌÚ U»æð mæúuæ ÂýâæÚU æ ð çü Îæð ÅðUÙæ æð ð Õè è çï Ì ÎëçcÅU ÚðU¹èØ ÎêÚUè ð çü ÃØ Á ÂýæŒÌ èçá Ð What is space wave propagation? State the factors which limit its range of propagation. Derive an expression for the maximum line of sight distance between two antennas for space wave propagation. 21. (a) ç âè ÚUðçÇUØæð ç ÅUß ÙæçÖ ð Ù êùð ð ÚðUçÇUØæð ç ÅUß ÿæø è ÎÚU ð çùø ð çü»ç æìèø ÃØ Á ÃØéˆÂóæ èçá Ð (b) ç âè çî» ÚðUçÇUØæð ç ÅUß ÙæçÖ è æñâì æøé â ð ÿæø-çsíúuæ (ç߃æåuùçsíúuæ ) âð ç â Âý æúu â Õ çïì ãñ? (a) (b) Derive the mathematical expression for law of radioactive decay for a sample of a radioactive nucleus. How is the mean life of a given radioactive nucleus related to the decay constant? 10

11 22. (i) æð ü ÂÎæü ç âè çõ Õ âð 100 cm ÎêÚUè ÂÚU çsíì ãñð â ÂÎðü ÂÚU ç âè žæü Üð â è Îæð çsíçìøæð, çáù ð Õè è ÎêÚUè 20 cm ãñ, ð çü ÂýçÌçÕ Õ ÕÙÌð ãñ Ð Üð â è È æð â ÎêÚUè ÂçÚU çüì èçá Ð (i) æð ü çöâæúuè Üð â ç âè ÂâæÚUè Üð â ð â æÿæ â  ü ð ÚU¹æ ãñ ÌÍæ ÎæðÙæð Üð âæð è È æð â ÎêçÚUØæ â æù ãñ Ð â â ØæðÁÙ æ È æð â ÎêÚUè Øæ ãñ? A screen is placed at a distance of 100 cm from an object. The image of the object is formed on the screen by a convex lens for two different locations of the lens separated by 20 cm. Calculate the focal length of the lens used. A converging lens is kept coaxially in contact with a diverging lens - both the lenses being of equal focal length. What is the focal length of the combination? ¹ ÇU - Î SECTION - D 2. âè æ ð æ æ Áè æð ÇUæò ÅUÚU Ùð çsìc æ MRI ( é Õ èø ÙéÙæÎ ç æ æ) ý ßèÿæ æ ÚUæÙð æ ÂÚUæ àæü çîøæð â ð æ æ Áè æð Øã ã»æ Ü»æ æñúu ßð âð SÍç»Ì ÚUÙæ æãìð ÍðÐ ÁÕ âè æ æð Øã ææì ãé æ, Ìæð âùð ÂÙð ÂçÚUßæÚU âð âãæøìæ Üè æñúu ÇUæò ÅUÚU âð â  ü Öè ç Øæ ÌÍæ ãæð Ùð Öè ÜæÁ ð ¹ ü ð ÖæÚUè ÀêUÅU ÎðÙð æ æàßæâù çîøæð â ð Âà æì âè æ Ùð ÂÙð æ æ Áè æð â ÂÚUèÿæ æ ð çü Ùæ çüøæ, Ìæç Ù ð çsìc è çsíçì ð ÕæÚðU ð ææì ãæð â ð Ð ÂÚUèÿæ æ âð ÂýæŒÌ ÁæÙ æúuè Ùð ÇUæò ÅUÚU æð ç Ì ÜæÁ ÚUÙð ð ˆØçÏ âãæøìæ ÎèÐ ÂÚUæð Ì»læ àæ ð æïæúu ÂÚU Ùè ð çî» ÂýàÙæð ð žæúu ÎèçÁ Ñ (a) æâ ð çß æúu âð âè æ, â ð ÂçÚUßæÚU ÌÍæ ÇUæò ÅUÚU mæúuæ ç Ù êëøæð æð ÎàææüØæ»Øæ ãñ? (b) MRI ÂÚUèÿæ æ ð ˆØçÏ ã»ð ãæðùð æ Øæ â ÖæçßÌ æúu æ ãæð â Ìæ ãñ? (c) Øã æùìð ãé ç MRI ÂÚUèÿæ æ 0.1 T ð é Õ èø ÿæð æ æ ÂØæð» ÚU ð ç Øæ»Øæ, Ìæð â ÂýæðÅUæòÙ ( æßðàæ C) ÂÚU, Áæð 10 4 m/s è æü âð»çì æù Íæ, é Õ èø ÿæð æ mæúuæ æúuæðçâì ÕÜ æ çù ÙÌ æñúu çï Ì æù ææì èçá Ð 4 11

12 Sssms s uncls wss sdvissd bs sis doctor to ssvs sn MRI (Msgnstic Rssonsncs Imsging) scsn of sis brsin. Hsr uncls fslt it to bs sxpsnsivs snd wsntsd to postpons it. Wssn Sssms lssrnt s bout tsis, s ss took tss s slp of s sr fsmils s nd s lso spproscssd tss doctor, wso s lso offsrsd s s ubstsntisl discount. Sss tssn convincsd s sr uncls to undsrgo tss tsst to s nsbls tss doctor to know tss condition of sis brsin. Tss informstion tsus obtsinsd grsstls sslpsd tss doctor to trsst sim propsrls. Bsssd on tss sbovs psrsgrsps, snswsr tss following qusstions : (a) What according to you are the values displayed by Seema, her family and the doctor? (b) What could be the possible reason for MRI test to be so expensive? (c) Assuming that MRI test was performed using a magnetic field of 0.1 T., find the minimum and maximum values of the force that the magnetic field could exert on a proton (charge C) moving with a speed of 10 4 m/s. ¹ ÇU - Ø SECTION - E 24. (a) ÂØé Ì æúðu¹ è âãæøìæ âð ç âè Õæs çßléì ÿæð æ ð çsíì ç âè æü æñúu ÂÚUæßñléÌ ð ÃØßãæÚU ð çßöðîù èçá Ð ÏýéçßÌ ÂÚUæßñléÌ ç â Âý æúu êü çßléì ÿæð æ æð M Âæ ÌçÚUÌ ÚUÌæ ãñ? (b) ÏæçÚUÌæ C ð ç âè â ÏæçÚU æ æð emf E è ç âè ÕñÅUÚUè mæúuæ Âê æüìñ æßðçàæì ç Øæ ÁæÌæ ãñð â ð Âà æì â æ ÕñÅUÚUè âð â  ü æåu çîøæ ÁæÌæ ãñð Õ ØçÎ â ÏæçÚU æ è Âç^ æ æð ð Õè æ ÂëÍ Ù Îæð»éÙæ ÚU çîøæ Áæ, Ìæð çù ÙçÜç¹Ì ð Øæ ÂçÚUßÌüÙ ãæð»æ? (i) â ÏæçÚU æ ð â ç Ì æßðàæð Âç^ æ æð ð Õè ÿæð æ è ÌèßýÌæÐ (iii) â ÏæçÚU æ mæúuæ â ç Ì ª ÁæüÐ ÂýˆØð çsíçì ð ÂÙð žæúu è ÂéçcÅU èçá Ð Íßæ (a) SÂcÅU èçá ç ç âè Öè æßðàæ-çß Øæâ ð çü ç âè Öè çõ Îé âð»éáúuùð ßæÜæ â çßöß ÂëcÆU â çõ Îé ÂÚU çßléì ÿæð æ ð çöü ÕßÌ ãæðìæ ãñð ç âè Ü æßðàæ (2q) ð æúu æ â çßöß ÂëcÆUæð æð æßðàæ ð æúu æ çßléì ÿæð æ ÚðU¹æ æð æð ÎàææüÌð ãé æúðuç¹ì èçá Ð 5 12

13 (b) Ùè ð æúðu¹ ð Îàææü ÙéâæÚU ÖéÁæ a ð ç âè â Õæãé ç æöéá ð àæèáæðz ÂÚU çsíì ÌèÙ æßðàææð ð çù æø æð ç߃æçåuì ÚUÙð ð çü ç ÁæÙð ßæÜð æøü ð çü ÃØ Á ÂýæŒÌ èçá Ð (a) (b) (a) (b) Distinguish, with the help of a suitable diagram, the difference in the behaviour of a conductor and a dielectric placed in an external electric field. How does polarised dielectric modify the original external field? A capacitor of capacitance C is charged fully by connecting it to a battery of emf E. It is then disconnected from the battery. If the separation between the plates of the capacitor is now doubled, how will the following change? (i) charge stored by the capacitor. field strength between the plates. (iii) energy stored by the capacitor. Justify your answer in each case. OR Explain why, for any charge configuration, the equipotential surface through a point is normal to the electric field at that point. Draw a sketch of equipotential surfaces due to a single charge (2q), depicting the electric field lines due to the charge. Obtain an expression for the work done to dissociate the system of three charges placed at the vertices of an equilateral triangle of side a as shown below. 1

14 25. (a) ÁÕ ç âè ÀUÇ é Õ æð,»ñëßðùæð èåuúu âð â ØæðçÁÌ, ç âè é ÇUÜè è æðúu Íßæ ââð ÎêÚU Ï ð Üæ ÁæÌæ ãñ, Ìæð»ñËßðÙæð èåuúu æ â ð Ì çßÿæðçâì ãæðìæ ãñð â çßÿæðâ æ ð çü žæúuîæøè ÂçÚUƒæÅUÙæ æð Âã æçù æñúu Ù æúu æð æ ËÜð¹ èçá çáù ÂÚU â çßÿæðâ æ æ ÂçÚU æ æ æñúu çîàææ çùöüúu ÚUÌè ãñð â ÂçÚUƒæÅUÙæ æ ß æüù ÚUÙð ßæÜð çùø æð æð çüç¹ Ð (b) ÁÕ æð ü Ü Õæ ü l æñúu ÂýçÌÚUæðÏ R è æü ÀUÇ PQ, ç æ ð Îàææü ÙéâæÚU â æù é Õ èø ÿæð æ ð çsíì ç âè æøìæ æúu æü ÂÚU æü v âð A æñúu C ð Õè é Ì M  âð ÏÚU- ÏÚU»çÌ ÚUÌè ãñ, Ìæð Ü â, emf æñúu ÕÜ ð ÂçÚUßÌüÙ æð æúðuç¹ì èçá Ð 5 Íßæ ç âè a.c. ßæðËÅUÌæ v5v m sinvt âð â ØæðçÁÌ LCR Ÿæð æè ÂçÚUÂÍ ð ÏæÚUæ ð çü ÃØ Á ÃØéˆÂóæ ÚUÙð ð çü $Èð ÁÚU æúðu¹ æ ÂØæð» èçá Ð Õ â ÂçÚUÂÍ ð ÿæçøì àæç Ì ð ÃØ Á ÂýæŒÌ èçá Ð Øã Îàææü ç ÙéÙæÎ ð â Ø çï Ì àæç Ì ÿæø ãæðìæ ãñð (a) (b) When a bar magnet is pushed towards (or away) from the coil connected to a galvanometer, the pointer in the galvanometer deflects. Identify the phenomenon causing this deflection and write the factors on which the amount and direction of the deflection depends. State the laws describing this phenomenon. Sketch the change in flux, emf and force when a conducting rod PQ of resistance R and length l moves freely to and fro between A and C with speed v on a rectangular conductor placed in uniform magnetic field as shown in the figure. 14

15 2R In s ssriss LCR circuit connsctsd to sn s.c. sourcs of voltsgs v5v 2 sinvt, uss psssor disgrsm to dsrivs sn sxprsssion for tss currsnt in tss circuit. Hsncs obtsin tss sxprsssion for tss powsr dissipstsd in tss circuit. Ssow tsst powsr dissipstsd st rssonsncs is msximum. 26. (a) ƒæê æüù ÚUÌð ÂæðÜÚUæòØÇU ð âð Îð¹Ùð ÂÚU æùð ßæÜð ÏýéçßÌ Âý æàæ è ÌèßýÌæ ð çß ÚU æ Øæð çî¹æ ü ÎðÌæ ãñ? (b) æúðu¹ è âãæøìæ âð Øã Îàææü ç Âý è æüù mæúuæ ç â Âý æúu âêøü âð æùð ßæÜæ Âý æàæ ÚñUç¹ ÌÑ ÏýéçßÌ ãæð ÁæÌæ ãñð ÌèÙ âßüâ ÂæðÜÚUæòØÇU àæèåu P 1, P 2 æñúu P â Âý æúu çöçß ØæçâÌ ãñ ç P 2 æñúu P ð ÂæçÚUÌ ÿæ P 1 ð ÂæçÚUÌ ÿæ âð ý àæñ 608 æñúu 908 æð æ ÕÙæÌð ãñ Ð ç æ ð Îàææü ÙéâæÚU P 1 ð âæ Ùð I 0 ÌèßýÌæ æ æð ü ÏýéçßÌ ß æèü Âý æàæ dæðì S çsíì ãñð ÂæðÜÚUæòØÇU P æð P 2 ð âæâðÿæ æð æ u508 æñúu 608 ÂÚU ƒæê æüù ÚUæÙð ÂÚU ç âè Âýðÿæ O mæúuæ çî¹æ ü ÎðÙð ßæÜð Âý æàæ è ÌèßýÌæ ææì èçá Ð 5 (a) (b) Íßæ Ø» ð çm çûæúuè ÂýØæð» ð ÂÍæ ÌÚU ð çü ÃØ Á ÃØéˆÂóæ èçá ÌÍæ ÂÎðü ð ç âè çõ Îé ÂÚU â Âæðáè ÃØçÌ ÚU æ æñúu çßùæàæè ÃØçÌ ÚU æ ð çü àæìðz ÂýæŒÌ èçá Ð Ø» ð çm çûæúuè ÂýØæð» ð ð ÎýèØ ç æcæu è ÌèßýÌæ I 0 ãñð â çõ Îé ÂÚU ÌèßýÌæ ææì èçá Áãæ ÂÍæ ÌÚU l 6, l 4 ÌÍæ l ãñð 15

16 (a) (b) Why does unpolarised light from a source show a variation in intensity when viewed through a polaroid which is rotated? Show with the help of a diagram, how unpolarised light from sun gets linearly polarised by scattering. Three identical polaroid sheets P 1, P 2 and P are oriented so that the pass axis of P 2 and P are inclined at angles of 608 and 908 respectively with the pass axis of P 1. A monochromatic source S of unpolarized light of intensity I 0 is kept in front of the polaroid sheet P 1 as shown in the figure. Determine the intensities of light as observed by the observer at O, when polaroid P is rotated with respect to P 2 at angles u508 and 608. OR (a) (b) Derive an expression for path difference in Young s double slit experiment and obtain the conditions for constructive and destructive interference at a point on the screen. The intensity at the central maxima in Young s double slit experiment is I 0. Find out the intensity at a point where the path difference is l 6, l 4 and l. 16