G.C.E. (A. L.) Support Seminar (g = 10 N kg 1 ) 1' SI unit of Wein's constant is, (1) m K (2) N K (3) W K (4) J K (5) kg K

Transcription

1 G... (. L.) Suppor Seminar - 14 Physics I Two hours Insrucions : * nswer all he quesions. * Selec he correc or he mos suiable answer. (g = 1 N kg 1 ) 1' SI uni of Wein's consan is, (1) m K () N K (3) W K (4) J K (5) kg K ' If is he elecrosaic capaciance and is elecric resisance, dimensions of is, (1) M () T (3) L (4) M 1 (5) T 1 3' paricle of mass m is projeced verically upwards wih velociy u. The resisance force F due o air moion is a consan value. The maximum heigh reached by he paricle is, (1) mu 4F () mu F (3) mu mg+ F 4' The graph of a force F wih ime, creaed on an objec of mass kg a res is shown in he figure. The momenum of he objec afer 5 s is, (1) 5 N s () N s (3) 5 N s (4) 3 N s (5) 35 N s (4) F (N) u 4g+ F 1 (5) mu (mg+f) (s) 5' Which one of he following is no an insance a which he velociy of he source exceeds he velociy of he wave propagaing hrough he medium? (1) Hearing a disincive sound when supersonic jes fly. () Formaion of whie waer waves a he ail of a fas moving boa on waer. (3) Observing of a whie mis a he ail of an aeroplane flying high in he sky. (4) Hearing a bursing sound when a whip is cracked. (5) Observing aseroids moving owards earh, in blue colour. 6' Two large uning forks and fixed o wo wooden boxes are placed close o each oher and when he uning fork is vibraed, he uning fork also vibraed wih maximum inensiy. If he prong of he uning fork is scraped and when hey are vibraed ogeher, 1 beas were heard during 5 s. Now when his uning fork is vibraed ogeher wih anoher uning fork of frequency 56 Hz, beas were heard during 5 s. Frequency of uning fork could be, (1) 54 Hz () 56 Hz (3) 58 Hz (4) 6 Hz (5) 64 Hz 7' If he magnificaion done by a convex lens when forming a real image of a real objec is M, he graph ha bes represens he variaion of 1/M wih he objec disance u is, 1/ M 1/ M 1/ M 1/ M 1/ M u u u u (1) () (3) (4) (5) u [ See page

2 - - 8' n sronomical elescope is made by using wo convex lenses of focal lenghs 1 cm and 6 cm' When a person observes he image of a disan objec forming a his near poin using he elescope, is l5 cm. The leas disance of he range a he disinc vision of his person is, (1) 6 cm () 5 cm (3) 3 cm (4) 1 cm (5) 15 cm 9' closed vessel conains only waer vapour. The pressure of waer vapour is P, while he sauraed 4 vapour pressure of waer vapour a his emperaure is P. The percenage of he waer vapour condensed, when he volume of he vessel is reduced o 1 h of he iniial value is, 8 (1) 4% () 5% (3) 6% (4) 7% (5) 8% 1' cerain hermomeer is incorrecly calibraed as 96 and a he upper and lower fixed poins, respecively. Is reading when i measures a emperaure read indicaed as 5 in a correcly calibraed hermomeer is, (1) 46 () 47 (3) 48 (4) 49 (5) 5 11' The radius and mean densiy of arh are and ρ respecively. cceleraion due o graviy a a poin on arh's surface is g. The acceleraion due o graviy a a poin on he surface of a plane wih radius and mean densiy 3 ρ is, g (1) () g (3) g (4) g (5) 3g 3 3 1' long wire is folded o form a par of a circular loop of radius r as shown. Magneic flux densiy a he cener of he loop when a curren I flows hrough he wire is, (1) μ o I ( 3 + ) 8r π () μ o I ( ) 4r π (3) μ o I ( 3 ) 8r π (4) μ o I I ( 3 1 ) 4r π 13' The peak curren of he supply conneced across he resisor shown in he diagram is I o. The mean dissipaion of power in he resisor is, (1) 1 I () I o o (4) I o (5) I o (3) I o ~ r (5) μ o I ( ) 8r π 14' The inernal resisances of he cells and ammeers in he circui shown in he diagram are zero. If he swich is closed and P and Q are shor circuied wha can happen o he ammeer readings? ( 1 > ) 1 1 (1) eading 1 eading Increases Increases P S Q () Increases Decreases (3) Decreases Decreases (4) Decreases Increases (5) qual o qual o 1 [ See page 3

3 - 3-15' The inernal resisance of he volmeer shown in he circui diagram is 1 Ω. When he swich is closed, he volmeer reads 4 V. Value of he resisor is, (1) 5 Ω () Ω (3) 5 Ω (4) 1 Ω (5) Ω 1 V r = 1 Ω V 16' If he Young's modules of wo wires and of equal lengh are Y and Y, respecively, he raio Y : Y = 3 :. The raio beween he areas of cross - secion of and, is : 1. ligh rod D is aached horizonally o he lower ends of and. If he rod exiss in equilibrium horizonally when a load W is hanged a a poin G on he rod, he raio G : GD is, (1) 1 ( () 1 ( 3 (3) ( 1 (4) 3 ( 1 (5) 4 ( 1 l G W l D 17' hin circular meal plae of radius is suspended from a sring, and is immersed in waer as shown in he diagram. The graph ha he mos accuraely indicaes he variaion of he ension (T) of he sring wih he deph (h) he plae immersed is, T T T T T h h h h h (1) () (3) (4) (5) 14 18' Given below is he decay of a radioacive carbon nucleus ( 6 ) N + X 6 7 X could be, (1) an α paricle. () a β paricle. (3) a γ phoon. (4) a neuron. (5) a proon. T h 19' Shown in he diagram is an insance ha he radiaion of frequency being greaer he han hreshold frequency inciden on he cahode of a phoo cell: onsider he following saemens () When he volmeer reading is increased by he rheosa, he ammeer reading also increases. () When he inensiy of he inciden radiaion is increased, he ammeer reading also increases. () The ammeer shows a reading even when he elecric cell is removed. Which of he above saemen/s is/are rue? (1) () only () () only (3) () only (4) () and () only (5) () and () only V [ See page 4

4 - 4 - ' Shown in he diagram is how forces F are applied perpendicularly o he handles of a cracker when cuing an arecanu. If he equilibrium insance is given in he diagram, he force exered on one side of he arecanu is, (1) F () F (3) 4F (4) 5F (5) 6F l 5l F F 1' When he king coconu is pierced a op as shown, he liquid of densiy ρ in i will rise o a maximum heigh h. If his liquid can be considered as a non viscose incompressible liquid, he excess pressure inside he king-coconu over he amospheric pressure before i was pierced is, (1) hρg () hρg (3) 1 hρg (4) hρg (5) hρg h liquid ' n objec moves wih a uniform acceleraion on a smooh horizonal plane, saring from res and obain a velociy v during a ime of n seconds. The displacemen of he objec wihin he ime inerval from (n ) seconds o n seconds is, (1) nv (n+1) () nv (n 1) (3) v n (4) v(n 1) n (5) v(n 1) n 3' Two concenric conducing cruss of radii a and b (b > a) are given respecive charges +Q and Q. The graph ha indicaes he variaion of he elecric field inensiy wih he disance r from he cener is, a b r a b r (1) () (3) (4) (5) 4' Three infiniely long sraigh conducing wires carrying 5 curren in each, are placed across hree verices,, of an equilaeral riangle of side 5 cm as shown. The magniude of he force per uni lengh of he wire kep a and he direcion are given by, (μ = 4π 1 7 Hm 1 ) (1) N m 1 () N m 1 (3) 1 5 N m 1 (4) 1 5 N m 1 (5) N m 1 a b r a b r 5 5 5' 44 g of O gas and 64 g of O gas a he same emperaure conain separaely in wo idenical conainers. If he pressure creaed by he O gas is P, he oal pressure inside he conainer when boh gases are insered ino one of he wo conainers is, (1) P () 1.5 P (3) P (4).5 P (5) 3 P 6' ccording o he equaion ΔQ = ΔU + ΔW in hermodynamics, a he change of sae of waer o vapour, () ΔU = () ΔW > () ΔQ > Which of he above saemen/s is/are rue? (1) () only () () and () only (3) () and () only (4) () and () only (5) ll (), () and () a b r 5 [ See page 5

5 - 5-7' mass m is suspended o a ligh inexensible sring, which passes around a smooh ligh pulley. The sring is ligh and. I is aached o wo idenical springs of spring consan k each as shown in he diagram. The periodic ime of he sysem is, (1) π m () π k m (3) π k m k (4) π m k (5) π m k 8' resonance pipe wih end correcion e is fully immersed in waer, and is hen gradually raised while vibraing a uning fork a is open end. The difference in lenghs of he firs wo resonaing siuaions is L. If he speed of sound in air is V, he frequency of he uning fork could be, (1) V L+e () V L+e (3) V L+e (4) V L (5) V L 9' When a weigh is aached o a sonomeer o provide a ension, he minimum lengh ha resonaes wih a uning fork is l 1. When his weigh is fully immersed in waer, he minimum lengh ha resonaes wih he same uning fork is l. The relaive densiy of he subsance of he weigh is, (1) l 1 () l 1 (3) l 1 (4) l (5) l 1 l l 1 l l 1 l l 1 l 3. volume of a liquid of densiy ρ 1 and mass m 1, is mixed wih an equal volume of a liquid of mass m and densiy ρ. If he mixure volume is no reduced, he densiy of he mixure is, ρ (1) 1 ρ () ρ ρ 1 ρ (3) 1 + ρ (4) ρ 1 + ρ (5) ρ + ρ The weigh of an objec in air is 45 N. Is weigh when fully immersed in a liquid is N. When he emperaure of he liquid is raised by 1, he weigh of he objec fully immersed in he liquid is 44.6 N. If he volume expansion of he objec wih increasing emperaure is negligible, he co-efficien of volume expansion of he liquid is, (1) K 1 () K 1 (3) K 1 (4) K 1 (5) K 1 3. The rod is suspended horizonally by wo srings as shown in he diagram. If he cener of graviy of he rod is G, he raio G G is, 3 6 (1) 3 : 1 () 3 : 1 (3) 1 : 3 (4) 1 : 1 (5) 1 : 3 '' '' m 33. Levels of inensiy of wo sounds which approach a cerain place a wo insances are d and 6 d. If he inensiies received due o hese wo sounds a his place are I 1 and I, respecively, he raio I 1 is equal o, I (1) 1 6 () 1 4 (3) 1 (4) 1 (5) 1 4 [ See page 6

6 ray of ligh in a medium of refracive index 3 ravels ino anoher medium of refracive index 4 a an angle of incidence of 3. onsider he following saemens. 3 () Deviaion of he ray is 3 ' () The ray is subjeced o oal inernal reflecion. () efraced ray is perpendicular o he parially refleced ray. True saemen/ saemens is/are, (1) () only () () only (3) () and () only (4) () and () only (5) () and () only 35. The equivalen resisance of he resisor nework beween and in he diagram is, (1) () (3) 3 (4) (5) Shown in he graph is he variaion of he ammeer reading wih he volmeer reading when he resisance in he circui is changed. The elecromoive force and he inernal resisance of he cell respecively, (1) V,.5 Ω () V, 1 Ω (3) V, Ω (4) 4 V, 1 Ω (5) 4 V, Ω 37. Shown in he graph is he variaion of he elecrosaic poenial (V) wih he disance (r) in an elecrosaic field. The graph ha bes expresses he corresponding variaion of he elecrosaic field inensiy () is, V I () r 4 V V (V) r r r r r (1) () (3) (4) (5) 38' The equivalen capaciance beween and in he sysem shown, which consiss of six idenical capaciors each having a capaciance is, (1) 6 () (4) (5) 6 (3) r [ See page 7

7 wooden cube is released from res a he op of a rough inclined plane of angle of inclinaion θ, over which a layer of oil is uniformly disribued. If he velociy- ime curves for he moion of he cube corresponding o he siuaions θ = 35 and θ = 45 are represened by he curves () and (), respecively, he mos suiable graph ha represens and curves is, v () () v () () v () () v () () v () () (1) () (3) (4) (5) 4. Shown in he diagram is a circui wih a Silicon ransisor. The value of V is approximaely, (1).7 V () 3.3 V (3) 3.7 V (4) 4.3 V (5) 4.7 V 41. mong he gae circuis given below, which circuis give S - flip flop. 4. S Q Q S () () () Q Q S Q Q 5 V.3 kω 4.3 kω (1) () only () () only (3) () and () only (4) () and () only (5) ll (), () and () 3 Ω 5 V Vin 1 Ω + +1 V 1 V Vou V in 5 V 5 V If he variaion of he inpu volage is as shown, he variaion of he oupu volage could be, Vou Vou Vou (1) () (3) Vou Vou (4) (5) [ See page 8

8 monochromaic ligh ray inciden on he surface PQ P of a prism of angle of prism 9, refracs and inciden on he surface P a is criical angle. efracive index of he prism subsance is. onsider he following saemens. 3 Q () riical angle for glass is 6 () ngle of incidence on PQ > 3 () ngle of incidence is equal o he angle of deviaion. True saemen/s is/are, (1) () only () () and () only (3) () and () only (4) () and () only (5) ll (), () and () 44. heaing coil of power 9 W is submerged in a meal block as shown and he block is suspended in a room of emperaure 3. When he heaing coil is swiched on, he emperaure of he block increases o 8 and hen become seady. Now when he heaing coil is swiched off, he meal block begins o cool down a a rae of.18 s 1. Hea capaciy of he meal block is, (1) 1 J K 1 () J K 1 (3) 3 J K 1 (4) 4 J K 1 (5) 5 J K solid subsance kep inside a vessel of negligible hea capaciy, is heaed a a consan rae. The variaion of is emperaure wih ime is shown in he figure. If he specific hea capaciy of he solid subsance is 1 J kg 1 K 1, is specific hea capaciy in he liquid sae is, (1) 6 J kg 1 K 1 () 7 J kg 1 K 1 (3) 8 J kg 1 K 1 (4) 9 J kg 1 K 1 (5) 1 J kg 1 K 1 θ (s) 46. Two circular conducing discs and are placed near a long sraigh wire as shown in he diagram. The wire is kep in he same plane of he disc and his plane is perpendicular o he plane of disc. If he curren (I) flowing hrough he wire varies wih ime () is shown in he graph, which one of he following saemens made abou he elecromoive forces induced in he discs and is correc? (1) During he period ( - 1 ), eddie curren loops are creaed in disc in he ani clockwise direcion and in disc in he clockwise direcion. () During he period ( 1 - ) eddie curren loops are creaed in disc in he ani clockwise direcion and in disc in he clockwise direcion. I I 1 (3) During he period ( - 1 ), eddie curren loops are induced in disc in he clockwise direcion and in disc in he ani clockwise direcion. (4) During he period period ( - 1 ), eddie curren loops are induced in disc in he clockwise direcion and hey are no induced in disc. (5) During he period ( 1 - ) eddie curren loops are induced in disc in he clockwise direcion and are no induced in disc. [ See page 9

9 If he galvanomeer reading in he circui shown is zero, he value of is, (1) Ω () 3 Ω (3) 4 Ω (4) 5 Ω (5) 6 Ω Ω G 1 Ω r = 1 V 48. moor vehicle of mass M moves on a banked rack of inclinaion θ, performing a horizonal circular moion in a pah of radius r, wih a maximum velociy V, wihou skidding off he rack. If is he normal reacion, beween he vehicle and he rack. F is he maximum fricional force and μ is he co-efficien of saic fricion, consider he following saemens, () cosθ F sinθ = Mg () sinθ F cosθ = MV r () F = μ True saemen/ saemens are, (1) () only () () and () only (3) () and () only (4) () only (5) ll (), () and () 49. uniform disc of mass 1 kg and radius 1 cm can perform a free roaion abou is cener O. narrow column of waer spirs a a speed of m s 1 from a horizonal pipe wih a cross secion of 1 mm, srikes he circumference of he disc angenially and leaves he disc wih a speed of 15 m s 1 as shown. The angular acceleraion obained by he disc, due o he srike of he waer column is, θ O 1 15 m s m s 1 (Momen of ineria I of a uniform disc of mass m and radius r is given by I = 1 mr, waer ρ = 1 kg m 3 and ignore he graviaional forces) (1).1 rad s ().1 rad s (3).1 rad s (4).5 rad s (5) 5 rad s densiy of 5. circular wire loop is placed symmerically o wo magneic fields of equal magniudes and opposie direcions as shown in he diagram. If he loop is roaed wih a consan angular velociy abou he axis xy, he graph ha repesens he mos accurae variaion of he elecromoive force induced in he loop wih ime is, x y (1) () (3) (4) (5) * * *

10 G...(. L.) Suppor Seminar - 14 Physics II Three hours Insrucions ( * Par : nswer all he quesions. * Par : nswer only four quesions. Par - Srucured ssay (g = 1 N kg 1 ) 1. cylindrical vessel filled wih waer o a heigh H, is placed on a horizonal surface as shown. small hole is pierced on is curved surface a a deph h from he waer surface. (a) (i) Obain an expression for he velociy v of waer ejeced from he hole, in erms of h and graviaional acceleraion g. (ii) Sae he principle you used o obain his expression. '''''''''''' H h x (iii) Sae he condiions under which his principle is valid. (b) Waer ejeced from he hole is inciden on he horizonal surface a a disance x from he foo of he cylinder. (i) Obain an expression for he ime consumed by a drop of waer ejeced from he hole o inciden on he surface, in erms of H, h and g. (ii) Obain an expression for x in erms of H and h. [See page

11 - - (c) (i) If H = cm find he values of x corresponding o he values given for h in he able. h (cm) x (cm) (ii) Using he values obained in par (c) (i), draw he rough skech of he graph o express he variaion of x wih h. x (cm) h (cm) (iii) Sae a conclusion ha can be made abou he value of x, using his graph. (d) If his cylinder filled wih waer is allowed o fall under graviy saring from res, from a cerain heigh, having is axis verical, wha can you commen abou he velociy of flow of waer from he hole? [See page 3

12 . Shown in he diagram is an incomplee apparaus designed by a suden o deermine specific laen hea of vaporizaion of waer. (a) (i) Sae he pracical difficuly faced when ube is used as shown in he diagram glass ube seam generaor glass ube D calorimeer (ii) Wha is he requiremen fulfilled in he experimen, by placing he ube accuraely? (iii) Draw and label he par ha mus be aached o he end of ube, in order o carry ou he experimen accuraely. (b) Name he par D and sae he use of i, (c) If he calorimeer is well insulaed from hea, wha is he precauion ha should be aken o furher improve he accuracy of he experimen? (d) (i) Sae he measuremens aken in he order of proceeding he experimen using he usual symbols [See page 4

13 - 4 - (ii) Wrie an expression o deermine he specific laen hea of vaporizaion L of waer in erms of he symbols used in par (d) (i) above. (Specific hea capaciy of calorimeer and sirrer is and specific hea capaciy of waer is w ) (e) Why is i imporan o ge a very accurae value for he mass of vapour? 3. Laser rays are significanly used in various fields. (a) (i) Wrie wo properies of Laser rays. (ii) Sae wo insances where laser rays are used pracically. Shown below is a se-up used o sudy refracion of ligh using laser rays. is a righ - angled prism made of plasic of refracive index (=1.414). When a laser ray is inciden a righ angles on surface, a ligh spo forms a Y on he screen when he prism is kep as shown while a ligh spo forms a X on he screen when he prism is removed. (b) (i) omplee he pah of he ray given, on he diagram. (ii) Mark he posiions of X and Y on he screen. Laser beam P 5 Screen r (c) If he disance beween X and Y is s, obain an expression including he angle of deviaion d in erms of r and s. (d) If he prism is slowly roaed in he clockwise direcion abou he poin P, he ligh spo will disappear a one insance. (i) Wha is he reason for his? [See page 5

14 - 5 - (ii) Find he angle a which he laser ray mus inciden on he surface, a he disappearance of he ligh spo as menioned in d (i) above. (iii) Find he angle of refracion of he ray a he surface a his insance. (iv) If he prism mus be roaed by an angle α o obain he above insance, wrie an expression relaing α and he angle of refracion a surface. (Simplificaion is no required). 4. Shown in he diagram is a coil of wire consising N number of urns carrying a curren I, placed in a uniform magneic field of flux densiy. rea of cross secion of he coil is. (a) Wrie an expression using given symbols for he orque τ ha exers on he coil when he plane of he coil incline by an angle α o he uniform magneic field. I α (b) Draw a rough skech of a graph o express he variaion of τ wih α. [See page 6

15 (c) The moving coil galvanomeer is an insrumen made using a cerain mechanism in order o mainain a consan value for τ a any posiion of he coil. (i) Sae his mechanism. (ii) If he orsion consan of he spring pivoed o he coil of wire is and he angle of roaion of he coil is θ, wrie an expression for I using he answer in par (a). (iii) Sae how he following facors mus be adjused in order o increase he sensiiviy of he insrumen. Facor djusmen N (d) The inernal resisance of a moving coil galvanomeer which shows a full scale deflecion for a curren of 1 m is 1 Ω. (i) Sae how his insrumen should be modified o measure a maximum curren of 1. (ii) Wha wo oher iems should be conneced o he above moving coil galvanomeer in order o conver i o an ohmmeer? 1 (iii) Sae a special feaure ha you observe in he scale when he insrumen is used as an ohmmeer. (iv) Plo a graph for he variaion of he deflecion of he ohmmeer wih he resisance measured by he ohmmeer. * * [See page 7

16 - 7 - Par - ssay (g = 1 N kg 1 ) * nswer only four Quesions. 5. ead he paragraph given below and answer he quesions. Imporance of using alernaive sources of power as a soluion for he exising power crisis have been now confirmed. One such alernaive mehod idenified is o improve usage of windmills o conver wind power o elecric power. Wind energy is solar energy. small percenage of he solar radiaion approaching he earh is absorbed by he amosphere. s a resul of his irregular heaing in he amosphere, paerns of air circulaion occur. I is imporan o sudy how such sored energy in wind can be uilized economically and ecologically. Since Sri Lanka is an island his wased wind energy can be used by insalling wind mills near coasal areas of Sri Lanka. Wind mills conver kineic energy of wind o elecrical energy. The blades of he mill is conneced o curren generaors hrough a gear sysem using bels. The secion wih blades in he mill is called he urbine. majoriy of his power requiremen is fulfilled by hydro power. u hydro power alone is no longer sufficien as he power consumpion in Sri Lanka has increased. Therefore, mineral oil, coal and solar energy are also used, as alernaive sources of power o generae elecriciy. When deciding an alernaive source of power, he facors such as he durabiliy, he economical benefi of he mehodology, he abiliy for easy access o he source, minimum environmenal polluion and a minimum iniial capial are also considered. (a) (i) Name wo alernaive sources of power in addiion o hydro power and wind mills, ha can be used in Sri Lanka. (ii) Wrie hree facors ha mus be considered when using alernaive sources of power. (b) If he radius of a blade in a wind mill is r, he densiy of air is ρ and i can be considered ha wind blows wih an average velociy of v perpendicular o he plane of roaion of he blades in he mills, (i) Wrie an expression for he mass of air cu - off by a blade during a second. (ii) Wrie an expression for he kineic energy sored in his mass of air, in erms of r" ρ and v. (iii) onsidering ha 8% of he wind energy is exraced by he blades, wrie an expression for he rae of ransfer of energy from wind o he mill using he above symbols. (iv) If he radius of a blades is 1.4 m, densiy of air is 1. kg m 3 and he velociy of he wind is 36 km h 1, calculae he rae menioned in par (b) (iii) above. (c) If he angular velociy of he blades increased o 1 rad s -1 from zero during 1s, calculae he following considering ha he fricion due o roaion of blades is negligible: (i) The momen of ineria of he blades abou is axis of roaion. (ii) The angular acceleraion of he roaional sysem. (iii) The orque creaed by wind on he sysem. (d) If he fricion on he blades is considerable, calculae he following: (i) The new angular acceleraion of he sysem, if fricional orque is N m. (ii) The angular velociy of he blades obain afer 1 s, when hey roae wih his acceleraion saring from res. (iii) If he wind sops now, he number of cycles ha he sysem roaes, when i comes o res under he fricional orque above. (xpress he answers o he neares ineger.) [See page 8

17 6. (a) Wrie an equaion for he speed (V) of a ransverse wave propagaing hrough a sreched wire. Inroduce he symbols used (b) Source Seel wire (c) sraigh seel wire of lengh.5 m is aached o wo fixed poins horizonally a boh ends, and a source of veriable frequency is aached a one end as shown. The frequency of he source varies from 3 Hz o 1 Hz. Densiy of seel is 8 kg m -3, velociy of ransverse wave of he wire is 35 m s -1 and he ension of he wire is.15 N. onsider he lengh of he wire is consan: (i) (ii) Find he corresponding frequencies a which he wire can resonae wih he source. Find he maximum ension of he wire in order o observe he nex overone wihin he given range of frequencies. If he lengh of he wire menioned above in par (b) (i), exends by.49% of i's original lengh: (i) Find he young s modulus of he subsance of he wire. (ii) Now he source is removed from he wire and he end is clamped, and he wire is rubbed in parallel o he wire using a resin spreaded cloh, while keeping he end free. Find he velociy of he wave ha sending across he wire when rubbed. (iii) alculae he frequencies corresponding o he fundamenal and he firs overone in par (c) (ii) above. 7. (a) (i) Wrie an expression for he capillary rise h of waer, hrough a clean glass capillary ube of inernal radius r, when he ube is kep verically in waer, in erms of T, ρ, g and r. onsider ha he angle of conac for waer and glass is zero. (ii) When anoher capillary ube idenical o he one above is placed verically in air, he heigh of he waer column ha can be mainained inside is h 1 and he radius of curvaure of he waer meniscus a he lower end is r 1. Draw he shape of he waer meniscus a he lower end corresponding o each siuaion saed below. (I) h 1 = h (II) h 1 < h (III) h 1 > h (iii) Find he maximum value of h 1 in erms of h. (iv) Plo a graph for he variaion of r 1 wih h 1. (b) Shown is he diagram of a syringe made by combining a uniform plasic pipe of diameer of cross secion 1 mm wih a narrow meal pipe YZ having a uniform caviy of diameer 1mm. X Y Z The syringe is kep horizonally along, filled wih a liquid of a surface ension 7 1 N m 1. force is applied on he pison, o spray he liquid from he narrow pipe, in order o es he performance of he syringe. mospheric pressure = N m (onsider ha he angle of conac beween he narrow pipe and he liquid is zero.) (i) onsider ha he liquid is abou o spray from Z and find he pressure inside he liquid a Z. (ii) Find he pressure of he liquid a he poins Y and X. (iii) Plo a graph for he variaion of pressure wih he disance from X o. (iv) Find he minimum force ha mus be applied on he pison for he liquid o spray a Z. [See page 9

18 8. posiively charged paricle carrying a charge q, eners perpendicularly o a uniform elecric field of field inensiy wih a velociy V as shown in he diagram. magneic field of flux densiy is creaed from he moving charge, perpendicular o is direcion of moion. (a) (i) Wrie an expression for he force F creaed on he charged paricle by he elecric field. (ii) Wrie an expression for he magneic force F creaed on he charged paricle.. V (iii) learly mark he forces acing on he moving charge q (Ignore graviaional forces). (iv) learly draw he pahs of he charge when F > F, F < F and F = F. (b) The mass specromeer is an imporan insrumen used in aomic physics, which is based on forces acing on charged paricles moving in elecric and magneic fields. I consiss of hree main pars. (1) Ion source - mis ions wih differen velociies. () Velociy Separaor - Ions which move a differen velociies are sen hrough a uniform elecric field of field inensiy and a uniform magneic field of flux densiy perpendicular o each oher, and hence ions which move wih a definie velociy are aken ou from he hole P. (3) Phoographic Plae - This is placed in a uniform magneic field of flux densiy. The ions ha ener in o his field inciden on he phoographic plae. and creae sensaions. ion source V q velociy separaor small hole phoographic plae P charge q ejeced from he ion source eners he velociy separaor wih a velociy V. Obain he requiremens fulfilled, for he charge o leave or o no o leave from he hole P. Used he resuls obained in par (a) (iv) above. (c) Now consider a charge q of mass m eners perpendicularly o he uniform magneic field wih a velociy V. (i) Wha kind of a moion (a pah) will his charge show in he magneic field? (ii) Wha is he reason for his naure (pah) of moion? (iii) If his charge q inciden a a place a a disance d from P on he phoographic plae, obain an expression for he raio m /q in erms of d,, and. (d) The charges which ener he field from he velociy separaor, inciden a various places on he phoographic plae. Wha is he reason for his? (ssume ha he charge q on he paricles is consan.) (e) How can he above process be used in aomic physics for he separaion of isoopes? [See page 1

19 nswer only par () or () () Shown in he diagram is a circui ha consiss of hree cells wih negligible inernal resisances. (a) When he swich S is closed, (i) alculae he curren ha flows hrough each cell. (ii) Find he charge sored in each capacior. (iii) If he poins X and Y are joined ogeher wih a wire of negligible resisance, will he charge sored in capaciors vary? xplain your answer. Q 3μ F 1 P μ F 3 V V S Y 1. Ω 3 V X Ω 4 Ω 4 Ω () (a) (b) When he swich S is opened, wha will happen o he charges sored in he capaciors? xplain wihou any calculaion. (c) Now he sysem of capaciors removed and a resisor is conneced beween P and Q. Then he swich S is closed. poeniomeer and a volmeer wih a finie resisance are provided o measure poenial difference across his resisor. The given poeniomeer is made wih a uniform wire of lengh 1m and a driving cell of e.m.f V wih a negligible inernal resisance. (i) If he balanced lengh obained when he poeniomeer is used is 6 cm, wha will be he value of he resisor? (ii) If he value of is calculaed using he reading aken from he above volmeer, insead of he poeniomeer, will you ge he same answer as in par (c) (i)? xplain your answer. V = 1 V Shown in he diagram is a circui designed by a suden using a Silicon ransisor o illuminae a = 5k Ω LD bulb only a nigh using a ligh dependen LD V, m resisor (LD). The value of he resisance of he LD becomes very small during day ime and increases o a large value of a few MΩ during LD nigh. The LD requires a poenial difference of V for proper illuminaion a which a curren of m flows hrough i. The ransisor becomes sauraed when he LD bulb illuminaes. (i) When he LD bulb illuminaes properly, ^I& Find approximaely he poenial a. ^II& Find approximaely he value of. (ii) The LD bulb will illuminae properly, only in dark when = 1 and only in sligh darkness when =. ^I& ompare 1 and. ^II& Sae reasons for your answer. [See page 11

20 (b) Shown below is a circui of a securiy sysem ha can be used o inform he residens when he gae of a house is open. Then he buzzer (bell) fixed in he house is ringing. +1 V 1 4 LD LD +1 V UZZ Q 3-1 V Ligh emied from he LD will compleely inciden on he ligh dependen resisor (LD) when he gae is closed. When he LD is exposed only o he ligh of he LD, is resisance become low and a poenial drop of 6 V will hen build up across i. When he LD is no exposed o ligh, is resisance become high and a poenial drop of 9V will hen build up across i. Zener diode is used o give a consan volage (V ) o he invering inpu of he op-amp. I acs as a volage comparaor wih he volage (V ) of he non-invering inpu. (i) If he curren and he poenial drop across he LD when i is illuminaed are 1 m and V, respecively, find he value of he resisor 1. (ii) Find he poenial a when he ligh emied by he LD is no inciden on he LD. (iii) Wrie he magniude and he polariy of he volage a Q when, (I) V > V, (II) V < V. (iv) (I) Which one of he condiions menioned in par (iii) above mus be fulfilled for he buzzer in he circui o ring? (II) xplain your answer. (v) (I) Which one of Zener diodes wih he Zener volages.7 V,.48 V and 6.8 V should be seleced in order o fulfill he acion expeced from he circui? (II) Sae he reason for your selecion. (vi) If he power of he Zener diode seleced in par (v) (I) above is.5 W, (I) Find he maximum curren ha can be sen hrough i. (II) Find he value of. [See page 1

21 1. nswer only () or () () (a) Sae Newon s law of cooling. Sae he condiions under which i is valid. (b) suden designs an experimen o demonsrae he physical properies of wax using he above law. Solid wax was heaed uniformly and is emperaure was measured wih ime, unil he sae jus before i begins o vaporize. Draw he expeced graph of is emperaure wih ime. (c) The suden obained hese readings by heaing 1 g of wax in a calorimeer of hea capaciy 6 J kg 1, using a heaing elemen of 1 W. The deails obained by he graph are as follows. (Temperaure of he environmen is 3 ) The gradien of he angen drawn o he graph jus before wax begins o mel is 3 6 min -1 The consan emperaure obained by wax is 6 The ime ha he emperaure of wax remains consan is min. The gradien of he angen drawn o he graph jus afer wax compleely mels is 4 8 min -1 Specific hea capaciy of solid wax used above is 18 J kg 1 K 1. (i) Find he meling poin of wax. (ii) Find he rae of absorpion of hea by he calorimeer and wax, jus before wax begin o mel. (iii) Find he rae of loss of hea o he environmen a ha momen. (iv) alculae he specific hea capaciy of liquid wax and he specific laen hea of fusion of wax. (v) When hea is supplied coninuously o liquid wax, he observed ha afer a cerain siuaion wax remains as a liquid and is emperaure does no increase. xplain he reason for his and calculae his seady emperaure. () S D Large Screen Phoo Sensiive deecor 1 m S is a monochromaic poin source. The wavelengh and he power of he waves radiaed by his are 6 and 1 W, respecively. deecor of surface area of 4 cm is kep a he cener of he screen as shown. harge of an elecron = Plank s consan = J s Valociy of ligh = m s -1 onsider π = 3 (a) (i) Find he number of phoons inciden on uni area a he cener of he phoo screen during 1 s. (xpress your answer o one decimal poin) (ii) alculae he number of phoons inciden on he enire area of he deecor during 1s. (iii) If he efficiency of he phoo deecor is 9, find he number of phoo elecrons emied from he deecor during 1s. (iv) alculae he phoo curren. (b) If a cerain laser ligh of wave lengh 49 nm and of power.1 W is used insead of he monochromaic poin source S, (i) alculae he number of phoons emied by he laser source during 1 s. (xpress your answer o one decimal poin). (ii) When his ligh is inciden on he esium cahode of a phoo cell, elecrons are released only from % of he phoons of he beam, calculae he curren flowing ou from he phoocell. (iii) If he hreshold frequency is Hz, deermine he sopping poenial for hese emied elecrons. * * *