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This is the Set 1 of the Physics question paper of Class XII CBSE (Central Board of Secondary Education) examinations.
I Series : SMAIl I .~. Code No. 55/1/1 -m.r~. ~ ~ cpf ~-~ ~ 1f9-1f!B' Roll No. 'R~ml Candidates must write the Code on - the title page of the answer-book. • ~~CR'Bfcp~~-LBT~~1f!B'l1 t I • ~-LBT~~m'4ctr31k~~~~cpfwr~-~~1f9-1f!B''Rm I • ~~CR'Bfcp~~-LBT~30~t I • ~~Cf;l'3T\"frM&""IW~-«~,~Cf;l~~~ I - • ~ ~-LBT cpf ~ ~ ~ 15 fl:r;rGCf)f~ WIT Tf<iT ~ I ~-LBT Cf)ffqmur ~ ~ 10.15 ~ mr~ 110.15 ~~ 10.30 ~(lcpwr~~-LBT~~~~~~~~- ~'RCl#~~~1 • Please check that this question paper contains 11 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 e.m., the students will read the question paper only and will not write any answer on the answer script during this period. ~fCl~IW=t (~) PHYSICS (Theory) f.relfftrr WP! " 3 crutJ [~3fcn,' 70 Time allowed " 3 hours J [Maximum marks,' 70 (i) ~rrR'~t I (ii) s« rrR'-W 'R' ~ 30 rrR't I rrR' 1 '# 8 ncncf;' rrR' 31frr-HY,3f1«74 rrR' t 3#r ~ f!C1i 3fcnCfiT tI (iii) rrR' 9 '# 18 'R' ~ rrR' qj-3fcn t; CfiT rrR' 19 '# 27 'R' ~ rrR' rfFr 3fcn t CfiT 'ff'2lT rrR' 28 '# 30 'R' ~ rrR' rikr 3fcn CfiTtI 55/1/1 1 [P.T.O .. (iv) ~-q;r # "flrm W cnTt~ ::rif t I ~ qt 3fq;J ~ ~~ #, rfFr 3fq;J ~ ~ ~ # 3#r rifq 3fq;J ~ M JTRT # 3iIPflRCf) qq;:r ~ fcFi<:rr rp:ff t I # JTRT # 3fTTTc1iT m TJ<l qq;:r # -# cficrM ~~ it Cfif.:rr t I . (v) c$H¥H2< cf;- ~ qff 3F]11frr o:rtt. t I ~ ~ 3i16f:(2/Cf) 6T nT 3TJq HEjJIOICf)74 ?JR71lT CfiT w:WrCR"~t I (vi) ~ 3i16f~4Cf) 6T 3TJq HAfMf@H ~ H4HiCf)r cf;-1fFif CfiT ~ CR" ~ t: c = 3 x 108 m1s h = 6.63 x 10-34 Js e = 1.6 x 10-19 C \/ t: ~71 R ~ !-!o = 41t x 10-7 T mA-I ~ -- 1 = 9 x 109 Nm2C-2 t;: ~?l ( t'<oA III.) ) 41tEo . / 1a 1 me = 9.1 x 10-31 kg 1// ~ ~ t r to A- General Instructions : , }: ~J (i) All questions are' compulsory. ,I {e.) JJ ¥ (ii) There are 30 questions in total. Question Nos. 1 to 8 are very short answer type questions and carry one mark each. (iii) Question Nos. 9 to 18 carry two marks each, Question Nos. 19 to 27 carry three marks each and Question Nos. 28 to 30 carry five marks each. (iv) There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all three questions of five marks each. You have to attempt only one of the choices in such questions. (v) Use of calculators is not permitted. However, you may use log tables ifnecessary. (vi) You may use the following values of physical constants wherever necessary : c = 3 x 108 m1s h = 6.63 x 10-34 Js e = 1.6 x 10-19 C !-!o = 41t x 10-7 T mA-I _1_ = 9 x 109 Nm2C-2 41tEo me = 9.1 x 10-31 kg 1. M ~ ~$JlCf?;I•.;'j cnr f.:p:;, fcrqq ~ ~ fcrqq Cfft -31R ~ mm t cp;rr~ ~ ~ ~ fen ~ c);-~ $JlCf?;I'i ~ m ~ ~ TIfu CR" w t ? 1 When electrons drift in a metal from lower to' higher potential, does i't mean that all the free electrons of the metal are moving in the same direction? 55/1/1 2 2. M ~ 1K ~ ~ iJ)kI<il4 ~ Cf)f~ B CR:Cf) t 31tt ~ 1K ~ 60° CfiTur t I~ 1K ~ ~ iJ)klCh14 ~ ~~ l1H CR:Cf)Cf)f ~ ~ ? 1 The horizontal component of the earth's magnetic field at a place is B and angle of dip is 60°. What is the value of vertical component of earth's magnetic field at equator? 3. MM~cit~cit('lN-~Cfl1~lJ1111(~"#'~ I 1 Show on a graph, the variation of resistivity with. temperature for a typical . semiconductor. 4. M~~~~~~Cf)fl1H~Cf4T~~? 1 Why should electrostatic field be zero inside a conductor? 5. '3'ff ~'Dfu Cf)f;w:r~ ~ f.:1cffi:r"#1H, 1 l mm otrr ~ cit ~"Otrif (Mf 1600 A ~m~~t cit q{I~II41 fqfCfl{On I 1 Name the physical quantity which remains same for microwaves of wavelength ~ I ~ o 1 mm and UV radiations of 1600 A in vacuum. 6. fcRr ~ "# ~ ~ Gfjf~ 3iqCjdOiiCfi 'ffir, M ~ "# ¢ 1K Cfitq cit ~ ~ ~cit~~~? 1 Under what condition does a biconvex lens of glass having a certain refractive index act as a plane glass sheet when immersed in a liquid? 7. m"#~~~~'I' 31tt'2' ~m~1K~t 1~(ffi""#~~'tlffiICf)f l1H ~~~~wm, ~ '1' 31tt '2' "#mt;~'tlfficit~CFlTmrrr? 1 0 1 •• I 20 Predict the directions of induced currents in metal rings 1 andZ lying in the same plane where current I in the wire is increasing steadily. oJ . 10 > I •• 2 O~ 8. it-~ Cfl1 cit qRCfi(>'qOiI3lT ~ I 1 State de-Broglie hypothesis. 9. Cfitq ~ M W1 ~ ~ ~ m Cf)f~qCjdOiiCfi(I-l g) =~ t I~ 1K ~ ~ cit ~ ~, ~ ~~, ~ 3ITtlK ~ ~ ~41'"f1{T[1f1 Wt m, ~ ~ Cf)f~ CfiTur ~~? 2 l A raY_?-fighh incident on an eiluilat~J~~s§-Prism-4tg =~) moves' parallel to the base-line of the prism inside it. Find the angle of incidence for this ray. 55/1/1 3 [P:T:O. 10. fsM2M (~~ Q'"lIMlll (~~# -3RK(~ fufur<t I 2 ~. ~ ~ #, Rkif<:1f@(1 # ~ GT ct-~ Cf?T ~ ~ I (i) s:1':R~,1m (ii) ~ (9)'"l{lq~Cf) (iii) s:1~412{~ (iv) ~'lffiCf)~ Distinguish between 'Analog and Digital signals'. OR Mention the function of any two of the following used in communication system: (i) Transducer ..--< (ii) Repeater (iii) Transmitter (iv) Bandpass Fitter 1 / 11. "Q"Cf)"~ Cf?T~ ~~ ct.~.~.) E ~ 3iH1f{Cf) ~ 'r' ~ I ~ ~ cnT ~ ~ ~R1 ~R2 ~"Q"Cf)"~~~~lFIT~ 1~#~Cf?TllRf-ikiifChC1 ~~~#lWlTlFIT~: 2 (i) ~~#cAt~~~~ I (ii) ~~#~R1~~ I (iii) ~ ~ # R1 ~ R2 ~ ~ # ~41f"1C1' t I· (iv) ~ ~ # R1 ~ R2 m (*14iC1{)~ # ~41f\J1C1 t I dq{1Cffi~ ~ # ~ mu31T ct-llR, 0.42 A, 1.05 A, 1.4 A ?MT 4.2 A t I~, ~ 3ilq~4Cf) ~ ~ fcfl ~ mu31T ct- ~ llR dq{1Cffi ~ ct- ~ # m m I m, dq{1Cffi ~~ct-m~#~muct-llRCfJ1~~ I A cell of emf E and internal resistance r is connected to two external resistances R1 and R2 and a perfect ammeter. The current in the circuit is measured in four different situations: (i) without any external resistance in the circuit (ii) with resistance R1 only (iii) with R1 and R2 in series combination (iv) with R1 and R2 in parallel combination , • l\~\ ., <, it "\ ,.J ) 1 4:2 A, The currents measured in the four cases are dA2 A, t.05. A, 1.4 A and ••...~~~P'- but not (' ~ , necessarily in that order. Identify the currents corresponding to the four cases mentioned above. 55/1/1 (\ I 12. 00 iJ)klChlll ~ "Ch1 iJ)klChlll ~ - 2.6 x 10-5 ~ I ~ ~ fcn ~ fcRl ~ cpr iJ)klcNlI ~ ~? ~~ lJuIT cpr~ ~ I 2 5 The susceptibility of a magnetic material is - 2.6 x 10- . Identify the type of magnetic material and state its two properties. ~. ~ ~ cF"1ICflI{ om P ~ Q .q.~"Ch1 &arr R ~~ ~4HIl1~(1 ~ 'I' ~ m- w~ I ~fq;r.q. ~~ ~~~WTTflfT~fcn~~~¢~ ~klqttt ~ ~ ~ ~ it ~ 1f{ t I~ ~ ~ 1f{ -;)c: iJ)klChlll ~ cpr l1H ~ ~ fWT ~ ~I 2 Q I p • I Two identical circular wires P and Q each of radius E. and carrying current 'T are kept in perpendicular planes such that tney have a common centre as shown in the figure. Find the magnitude and direction of the net magnetic field at the common centre of the two coils. Q I p • 14. \iftif 00 ~ ~ coT00 m.m. ~ ~ ~ ~~ M \j'ffiIT ~ ill Cf# ~ ~ ~ mm, ~, ~.m. (~flOjlqffi) ~ -mo cpr ~ ~ 1f{ ~11I(11< ~ ~ mm ~~ I ~-~"Ch1 :8Cfl0F"I ~~1f{~01IT&IT~"Ch1\jff~~? I 2 When an ideal capacitor is charged by a de battery, no current flows. However, when an ac source is used, the current flows continuously. How does one explain this, based on the concept of displacement current? t15. 00 ~ coTOO~fWt~~(~~ 3Wffi 'Q' ~ ~ 'r' ~"&4, (i) ~~ I (E) ~ (ii) ~ fcrqq (V) ~ qRq~"i 2 Draw a plot showing the variation of (i) electric field (E) and (ii) electric potential d-- ' (V) with distance r due to a point charge Q. \/;:):; ~00~~~-~"Ch1~~ 1~~fcn'L' ~-~"Ch1oo~.q.I ~ ~ ~ ~ fWt ¢:tlq~lICfliJ)klcNlI ~ cpr l1H 2 u2 mrr~ I. 2 Define self-inductance of a coil. Show that magnetic energy required to build up the current I in a coil of self inductance L is given by ~ U2. 55/1/1 5 [P.T.O. 17. .am ~~ -It~ 'tffiT CfiTl1R (~mA), ql?ilf~f~ICfi~ -It~ 'tffiT ~l1R (~ JlA) ~ ~~ t 11ft m::nm ~CfiT ~ ql?ilf~~ICfi ~ -It~ ~ ~ t? 2 The current in the forward bias is known to be more (-mA) than the current in the reverse bias (-JlA). What is the reason, then, to operate the photodiode in reverse bias? y. fmT 'L' ~ 'L' ~ CI?T~ 'tWl CI?T~~, ~ 'tWl ~ ~ '0)' cnlufr:r ~ ~ ~ WiiIT ~ cwr:r (WT) ~ ~ 1R ~ ~ t ~ cpm fmT cwr:r CI?T~ ~ t fen, ~ ~ 1R~t I ~CI?T~~, cwr:r (WT) ~~~~~t ~cwr:r~~~<1klq~ t I~ ~ ~ ~ W1R iJ)klCf?l~ B, ~ fq~4H t I cwr:r (WT) ~ ~ ~ cwr:r ~ ~ ~t~.~. (fcIwr~GWl) ~m~~~~ I 2 A metallic rod of 'L' length is rotated with angular frequency of '0)' 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. Deduce the expression for the emf between the centre and the metallic .nng. 19. ~-It~LCR ~~~l"p:ITt~, L = 5.0 H, C = 80 JlF ~ R = 40 nt ----------/~ ~ 240 V ~ ~ '1ftqffi ~ ~~ ~ fi41f~C'I t I qRCfiW1 ~ : 3 R C L (i) ~ CI?Tcnlufr:r ~ ~~ 1R ~ CfiT qRilif(>lC'lCRffi t (ii) ~~1R~CfiTl1R, (iii) ~1R~~fuff~~crt~lFf(3W.~.~.) fcrqq-1:ffi1I The figure shows a series LCR circuit with L = 5.0 H, C = 80 JlF, R = 40 n connected to a variable frequency 240 V source. Calculate . R C L (i) The angular frequency of the source which drives the circuit at resonance. (ii) The current at the resonating frequency. (iii) The rms potential drop across the capacitor at resonance. 55/111 6 20. 00 4 em x 10 em ~ (3WfTll) ~~'3i14f11Cf)1{ ~ ('lm) ~ 2 A CfI1~~~ m -m ~ I fq;f (~ -q: ~ 11<l3fF1K, ~~ ~"ill{ f;rml 5 A ~ ~ ~ m -m t ~-qm ~ ~ 1ffiI' ~Pl<rr ~ I ~ ~"ill{ ~ -qm ~ tr 'Wl(ffi -q: m 'ill ~ ~ 3 I=5A 4 ern 2A 2A 10 ern 1 ern (i) -qm~lf{~qwrr(~~-~~~ (ii) ~ ~"ill{ ~ CfiRUT, -qm If{ ~ cnB ~ CfiTllftmuT (l1R) ~ ~ fWl I A rectangular loop of wire of size 4 ern x 10 em carries a steady current of 2 A. A straight long wire carrying 5 A current is kept near the loop as shown. If the l~and the wire are coplanar, find I=5A 4 ern 2A 2A 10 ern 1 ern (i) the torque acting on the loop and - / (ii) the magnitude and direction of the force on the loop due to the current carrying . ~ WIfe. r?--- -:If ~ 21. (31) ~ ~ ~ ~ ~ ~ Cfqh~.')Cf){OI ~ ~ ~ ~ ~ ~ ~ fcp '" t51~~l\l'H CfI1ncff' ~ ~ -q:, ~JlCf?;I'i CfI1~ CfiT l1R" ~ (~JlCf?;I'i ~ ~ m- w-ffi fI<II~t4 ~l1R" CfiT n 1fIT men- ~ I 3 0f) 00 t51~~hH ~ -q: ~ ~JlCf?;I'i mtq -q: ~ ~ ~ -q: ~ I~ ~ ~~Cf?;I'i 3llRT f'"lk\fllOi ~ (-3lID ~ -q: ~ \i'frl 'ill dfflMfI m~ qrffi ~Cf?;lOj') ~31T CfI1~ ~ fcmRt mm ? (a) Using Bohr's second postulate of quantization of orbital angular momentum show that the circumference of the electron in the nIl!orbital state in hydrogen atom is n times the de Broglie wavelength associated with it. (b) The electron in hydrogen atom is .initially in the third excited ~tate. What is the maximum number of spectral lines which can be emitted when it finally moves to the ground state ? 55/1/1 7 [P.T.O. \ ~. ,( "0 22. ;mW"#~CfiT~~(ffi" AB ~11<IT~, Fm#~~~~~R<m (3iqfhhil) fcrqq >fCJUTill rmD ~ I~ ~ ~ ~ CfiT, ~ ~ q(Yf ct.~.~.) 81 ('MT 82 t, ;mW"# ~ TT<l ~ B<ilF~d fcn<:rr ~ I ~ 11<IT m~ fcr~ ~ (~ ~ A fut-B 120 ern ('MT 300 em ¢'R'~m-illt I illmd"~ (i) 8/82 (ii) ~E1~m~~~(~~cR¢ I 3' ~ ~ cRB~~'i!?nMdl CfiT ~ \1fRfT ~ ? .----~ I 11----'\I\.KI\;f\,----. IE---- 300 em --~) 120cm~ A\--------..,.-~------'B t2 ~ fCflNICfl ~ mm CfiTMrr ~ ~~ "# :m=m=r ~ RCfiT md"~, 11R .4 Q ~-BCfiTt~~~m IA3i1rD~~~CfiT11Rmmd"~ I 1n E F D In 4n R A I Lt----' 9V B 3V C In the figure a long uniform potentiometer wire AB is having a constant potential gradient along its length. The null points for the two primary cells of ernfs 81 and 82 (~ \ connected in the mariner shown are obtained at a. distance of 120 em and 300 em from the end A. Find (i) 8/82 and (ii) position of null 'point for {he cell 81, How is the sensitivity of a potentiometer increased? .-----i I It-----J\/V'(/\I\,.----, IE---- 300 em --~) 120cm~ A~------..,.,.--~------'B 55/1/1 Using Kirchoff's rules determine the value of unknown resistance R in the circuit so that 'no current flows through 4 Q resistance. Also find the potential difference between A and D. A I Lt--~-J 9V B 3V C 23. . (i) CWfTUl ~ (A) ct 30 Cf 170 ct~ llRl, ctm, ~ ~-3lR"$:R ~ (BElA) ct lWf ct~ ~ ctr ~ ~cwil4 ~ ct~ ~lJUT ctrnr ctr ~ ~ t? (ii) ~ fcf>~ ct~~"!lftw# ~CfiT ~ ~ (f.:rm) Will t ~~ ~0lI4H ~ (A) w ~ (-311f~ ~ ~ I 3 (i) What characteristic property of nuclear force explains the constancy of binding energy per nucleon (BEl A) in the range of mass number' A' lying 30 < A < 170 ? (ii) Show that the density of nucleus over a wide range of nuclei is constant- independent of mass number A. 24. 00 fur.wr cnT41'§f<?1n fi8 ctr 3iIct~lICflnl t ~ C c ct ~ # cJ "Cfllt WCf)~ C I 3 00 \iiqlct¢f>lll dirT w,OO 41'§(1Cflfur.wr ct ~ ~ ~ ID1{f, 3W1Tl141'§f<?1n dirTCfiT~ctm, ~~~ I Write any two factors which justify the need for modulating a signal. Draw a diagram showing an amplitude modulated wave by superposing a modulating signal over a sinusoidal carrier wave. 25. CfiT 3i1~"1f2I~"1 ~-~ '84ICfl{OI ~ I~ ~ c ctr ~ '84ICfl{OI nT~-1k1CfJlll cttnTiR-m fClfCfl{On ct~ rm ~ ID1{f ~ ~"'8"Cflmt? 3 WPM ~ >I'llIcf ct &r ~ oourr CfiT~ ~ ~ c ~ '84ICfl{OI t ~ ~ ~ctr~~tl Write Einstein's photoelectric equation. State clearly how this equation is obtained using the photon picture of electromagnetic radiation. Write the three salient features observed in photoelectric effect which can be explained using this equation. 26. (31) ~ ~ OlIf('1Cfl{OI >W{f Cfi8 ctm qi~fn:j~,~-mffi ~ CfiT ~3ilct~4Cflt? 3 '01) <:frr ct~~ w:ITrr #, A dirT ~ ct ~CflctOn PM CfiT W ~ ~ lFIT t I ~ ~ / ct ~ ~ w, ~ 1f4RK A t~ ctr mwrr K ~ «(Rc:) t I 01, ~ ~ w WPMctrmwrr~~~w~~t I (a) Why are coherent sources necessary to produce a sustained interference pattern ? (b) In Young's double slit experiment using monochromatic light of wavelength A, the intensity of light at a point on the screen where path difference is A, is K units. Find out the intensity of light at a point where path difference is A/3. 55/1/1 9 [P.T.O. 27. ~ c)? ~ c)? ~ ~ 00 ~ fuRt 00 fq-qcf.:r ~ ~ cn1 cxn&rr~, ~ fuRt QCf)qOn~ ~ 00 ~ ~ I 3 ~ fuRl cn1 ~ CfiT~ mtm ~ ~~ 1fIT ~ ~ ~"ill, ~ ~ fq-qcf.:r ~c)?~~~1:R"CFn~~ ? Use Huygens's principle to explain the formation of diffraction pattern due to a single slit illuminated by a monochromatic source of light. When the width of the slit is made double the original width, how would this affect the size and intensity of the central diffraction band? 28. "QCfl ~ ~ c)? ~ CfiT~ ~ ~ ~ fyf"FH ~ CfiTR:cn1 ~ ~ mco m ~~I 5 W~CfiT"QCfl41'l'1'"1Iqct ~~ a&~ Cf)1~fC!R:lCfiT~~ I CFnW~oo ~~~cn1 d-c'Clct4 WllT1:R"CfiTt~m~? ~~ I are:rcrr (.:31) ~1R1CRlcn1~~ I WCfiT~.~. (S.I.) ~CFn~? 01) TTm1 c)? ~ c)? ~ 00 ftr.& ~ fcn, 00"QCfl"W1R ~ ~ ~ -3FRf W«Wf WR:~ c)? Cffi1JT00 ~ 1:R" ~ ~ CfiTliR, ~ ~ ~ ~ cn1 ~ f.:M\ 1:R" ~ ml 0) w~ cn1 mrr CFn mm, ~WR: ~ (i) ~HI~~lct m (ii) 5fi01I~~lct m ? Explain the principle of a device that can build up high voltages of the order of a few million volts. Draw a schematic diagram and explain the working of this device. Is there any restriction on the upper limit of the high voltages set up in this machine? Explain. OR (a) Define electric flux. Write its S.1. units. , (b) Using Gauss's law, prove that the electric field at a point due to a uniformly charged infinite plane sheet is independent of the distance from it. I, (c) How is the field directed if (i) the sheet is positively charged, (ii) negatively charged? 29. 'i<i!O!(\Cf)cn1~@ffiTcn1~C'MT~m~~ I 5 00 ~ 'i<i!O!(\Cf) ~ c)? a& ~ cn1 ~ ~~: 150 em·~ 5 em t IW ~ 'i<i!O!(\Cf) 3 km ¥~, 100 m ~ ~ w \l'fTCt "ill~ CfiT ~fctf~kI cn1 ~ ~ mm ~ ~fctfiiikl ~ ~ 25 em ~ ~ 1:R" I .are:rcn ~~m CfiT~ c)? 'i<i!O!(\Cf) ~ ~ fcRr ~ ~ m ~ ? 00~~c)?~~~cn1~~~: 1,25 em ~ 5 em t I ~ 30 CfiTufr:r~ mco ~ c)? fWt, ~ CfiT~ c)? ~&:r ~ mTfur~, ~ ~~ CfiT~ ~ it M~ ~ ~14Io:ljct: M\ifffiT ~ ? 55/1/1 10 Define magnifying power of a telescope. Write its expression. A small telescope has an objective lens of focal length 150 em and an eye piece of focal length 5 em. If this telescope is used to view a 100 m high tower 3 km away, find the height of the final image when it is formed 25 em away from the eye piece. OR How is the working of a telescope different from that of a microscope? The focal lengths of the objective and eyepiece of a microscope are 1.25 em and 5 em respectively. Find the position of the object relative to the objective in order to obtain an angular magnification of 30 in normal adjustment. 30. CE fcR"m ~ 00 S;if"1«O{ ~ ~ m~ ~ ~ ~ ~ I~ cnr<:T~ CfiT ~~ I ~~fcnw~CflT~~ Av = - PacRL, ~ Pac - '1:lRT~, rj RL -~~~rj-f.:r<ffi~t I 5 ~~~m~~5fiOII\4CflmCfiTcp:rr~t? ~ (31) ~ ~ ~ ~ <itlCflI<l m ~ ~ ant@ ~ ~ p-n ~ ~ ~ CfiT M ll<IT m I~ ~ ~ CfiT ~~ ~ Hcrm ~ f.:rrRf ~ ~ CfiT ~ I (Gf) f'"l8ifCfl('1 mm A ~ B ~ m f.:rrRf ~ ~ (Y) CfiT ~ : (i) OR ltc ~ (ii) NAND ltc t1 t2 t, t4 ts t6 t8 I I I I I I I I I I I I Ai----f BI-: -- •••••...• I I I Draw a simple circuit of a CE transistor amplifier. Explain its working. Show that the - - ------------ P R I voltage gain, A~, ofthe amplifier is given by Av = - a;, L, where Pac is the current 1 gain, RL is the load resistance and rj is the input resistance of the transistor. What is __ the significance of the negative sign in the expression for the voltage gain? OR (a) Draw the circuit diagram of a full wave rectifier using p-n junction diode. Explain its working and show the output, input waveforms. (b) Show the output waveforms (Y) for the following inputs A and B of (i) OR gate (ii) NAND gate t1 t2 t3 t4 ts t, t8 I I I I I I I I I I I I Ai----4 55/1/1 11