IEEE Physics Moel Question Paper ote: Question o. 11 to 1 an 1 to consist of Eight (8) marks each for each correct response an remaining questions consist of Four (4) marks. ¼ marks will be eucte for inicating incorrect response of each question. 1. In the given figure, Zener ioe is use as voltage regulator. In this set up, when input voltage changes a) I L will be constant I R S b) I L will increase with increase in V in an ecrease with ecrease in V in I Z I L c) I L will ecrease with increase in V in an increase with ecrease in V in V in V 0 RL ) I L will increase if I Z ecrease an I L will ecrease if I Z increases. In meter brige experiment as shown in figure the balance E point is at C. Length C = x. The value of C, if the raius of the wire is ouble will be a) x/ P Q G b) x l 100-l c) x/4 C 1m ) 4x. screen is place at a certain istance from a narrow slit which is illuminate by a parallel beam of monochromatic light. If the wavelength of light use in the experiment is λ an is the with of the slit, then angular with of central maximum will be λ a) sin b) sin c) sin ) sin 4. bove Curie s temperature a) a ferromagnetic substance becomes paramagnetic b) a paramagnetic substance becomes ferromagnetic c) a paramagnetic substance becomes iamagnetic ) a iamagnetic substance becomes paramagnetic 5. In an experiment, the angles are require to be measure using an instrument in which 9 ivisions of the main scale coincie with 0 ivisions of the vernier scale. If the smallest ivision of the main scale is half a egree (= 0.5 ), then the least count of the instrument is a) half minute b) one egree c) half egree ) one minute 6. Two full turns of the circular scale of a screw gauge cover a istance of 1 mm on its main scale. The total number of ivisions on the circular scale is 50. Further, it is foun that the screw gauge has a zero error of 0.0 mm. While measuring the iameter of a thin wire, a stuent notes the main scale reaing of mm an the number of circular scale ivisions in line with the main scale as 5. The iameter of the wire is a). mm b).7 mm c).67 mm ).8 mm 7. The shape of the graph between 1/u an in case of a convex lens is a) b) c) ) 1/u 1/u 8. The combination of D gates shown in the figure are equivalent to a) an R gate an an D gate respectively b) an D gate an a T gate respectively c) an D gate an a R gate respectively ) an R gate an a T gate respectively Photo current 9. The figure shows the variation of photocurrent with anoe potential for a photo-sensitive surface for three ifferent raiations. Let I a, I b an I c be 1/u 1/u c b a noe potential
the intensities an ν a, ν b an ν c be the frequencies for the curves a, b an c respectively. Then a) ν a = ν b an I a I b b) ν a = ν c an I a = I c c) ν a = ν an I a = I b ) ν = ν c an I b = I c 10. n element ecays into an element C by a two step process + He 4 an C + e. Then, a) an C are isotopes b) an C are isobars c) an C are isotopes ) an are isobars 11. galvanometer is connecte in figure as shown. It has resistance of 100 Ω. What shoul be resistances connecte to it in parallel so that its eflection is reuce to half? a) 100 Ω b) 91 Ω c) 99 Ω ) 95 Ω 1. thin ielectric ro of length l lies along x-axis with one en at the origin an the other en at the point (l, 0). It has a uniform charge istribution with total charge Q. The potential at a point (x, 0) when x > l is Q x l a) loge 4πε0l x b) Q x Q Q x loge c) ) loge 4πε0l x l 4πε0l πε0l x l 1. soli spherical region having a spherical cavity whose iameter R is equal to the raius of the spherical region has a total charge Q. Fin the potential at a point P as shown in ajoining figure. (ssume charge per unit volume is constant) 5Q Q P R a) b) 4πε0R 44πε0R Q 5Q R c) ) 16πε0R πε0r 14. The ominant mechanism for motion of charge carriers in forwar an reverse biase silicon p-n junction are a) rift in forwar bias, iffusion in reverse bias b) iffusion in forwar bias, rift in reverse bias c) iffusion in both forwar an reverse bias ) rift in both forwar an reverse bias 15. transistor is use in common emitter configuration. Given its α = 0.9, calculate the change in collector current when the base current changes by µ. a) 1 µ b) 0.9µ c) 0µ ) 18µ 16. Match the following ) Cyclotron P) To etermine the mass of isotopes ) Synchrotron Q) To accelerate ions C) Linear accelerator R) To accelerate neutral atoms D) Mass-spectrograph S) To accelerate electrons 17. force F acting on an object varies with istance x as shown in figure. The force is in an x in m. The work one by the force in moving the object from x = 0 to x = 6 m is F() a) 18.0 J 4 b) 1.5 J c) 4.5 J 1 S G 100Ω 1 V R=1kΩ 4 5 6 7 8 x(m)
) 9.0 J Passage: n initially parallel cylinrical beam travels in a meium of refractive inex µ(i) = µ 0 + µ I, where µ 0 an µ are positive constants an I is the intensity of the light beam. The intensity of the beam is ecreasing with increasing raius. 18. s the beam enters the meium, it will a) iverge b) converge c) iverge near the axis an converge near the periphery ) travel as a cylinrical beam 19. The initial shape of the wave front of the beam is a) convex b) concave c) convex near the axis an concave near the periphery ) planar 0. The spee of light in the meium is a) minimum on the axis of the beam b) the same everywhere in the beam c) irectly proportional to the intensity I ) maximum on the axis of the beam 1. Tangential acceleration (a t ) of a particle moving in a circle of raius 1 m varies with time t as shown in ajoining figure. Time after which total acceleration of particle makes an angle 0 with raial acceleration is (initial angular spee is zero) a) 4 s b) 4/ s c) / s ) s. large soli sphere has variable but raially symmetrical mass ensity changing with istance from the centre (r) as ρ = ρ 0 r n. For what absolute value of n, fiel intensity will be inepenent of r? a) 1 b) c) ) 4. The relation between time t an istance x is t = ax + bx, where a an b are constants. The acceleration is a) abv b) bv c) av ) av 4. Statement I: For a charge particle moving from point P to point Q, the net work one by an electrostatic fiel on the particle is inepenent of the path connecting point P to point Q. Statement II: The net work one by a conservative force on an object moving along a close loop is zero. a) Statement I is true, Statement II is false. b) Statement I is true, Statement II is true, Statement II is a correct explanation for Statement I c) Statement I is true, Statement II is true, Statement II is not a correct explanation for Statement I. ) Statement I is false, Statement II is true. 5. transmitting antenna is at a height of 0 m an the receiving antenna is at a height of 80 m. The maximum istance between them for satisfactory communication is (Raius of earth = 64 km) a) 16 km b) km c) 48 km ) 96 km 6. Figure shows a parabolic graph between T an 1/V for a mixture of gas unergoing an aiabatic process. What is the ratio of v rms an spee of soun in the mixture? a) / b) c) / ) 7. In an experiment, electrons are mae to pass through a narrow slit of with comparable to their e-roglie wavelength. They are etecte on a screen at a istance D from the slit (see figure). Which of the a t (m/s ) 60 Time (s) T T 0 T 0 of 1/V 0 4/V 0 1/V y=0 D
following graphs can be expecte to represent the number of electrons etecte as a function of the etector position y (y =0 correspons to the mile of the slit)? a) y b) y c) ) y y Directions: (Q.o. 8 an 9) Consier a block of conucting material of resistivity ρ shown in the figure. Current I enters at an leaves from D. We apply superposition principle to fin voltage V evelope between an C. The calculation is one in the following steps : i) Take current I entering from an assume it to sprea over a hemispherical ii) surface in the block. Calculate fiel E(r) at istance r from by using hm s law E = ρj, where J is the current per unit area at r. iii) From the r epenence of E(r), obtain the potential V(r) at r. iv) Repeat (i), (ii) an (iii) for current I leaving D an superpose results for an D. 8. V measure between an C is a) b) c) ) πa π (a + b) a (a + b) πa π (a + b) π(a b) 9. For current entering at, the electric fiel at a istance r from is a) b) c) ) 8πr r πr 4πr Key : (c) 0. For a transistor amplifier in common emitter configuration for loa impeance of 1 kω (h fe = 50 an h oe = 5 µ /V), the current gain is a) 5. b) 15.7 c) 4.8 ) 48.78 Key : 1) a ) b ) c 4) a 5) 6) 7) a 8) a 9) a 10) a 11) b 1) b 1) a 14) b 15) 16) Q,S,Q,P 17) b 18) b 19) 0) a 1) c ) a ) c 4) b 5) c 6) b 7) 8) c 9) c 0) I V I a b c C D
Hints an Solutions: 1. Voltage across Zener ioe remains constant.. P l = Q 100 l alancing length is inepenent of area of cross section of wire.. For 1 st λ minimum: sin θ = λ sin θ = θ = sin, angular with of central maximum is θ. 4. Conceptual 5. Here, 0 VSD = 9 MSD 9 1VSD = MSD 0 Least count = 1 MSD 1 VSD 9 1 1 1 = 1 MSD = MSD = 0.5 = = 1 ( 1 = 60 ) 0 0 0 60 6. Pitch of screw gauge = 0.5 mm Least count of the screw gauge = 0.5 mm = 0.01mm 50 Zero error = 0.0 mm Zero correction = +0.0 mm Main scale reaing = mm Circular scale reaing = 5 bserve iameter of the wire = mm + 5 (0.01) mm =.5 mm Correcte iameter of the wire = (.5 + 0.0) mm =.8 mm 1 1 1 7. = f v u 8. = = + = + It is the oolean expression of R gate. = = It is the oolean expression of D gate. 9. From the graph, we note that the saturation current is same for curves b an c but ifferent for curve a. Therefore, intensities of b an c will be equal but ifferent from that of a i.e. I a I b but I b = I c. s stopping potential is same for curves a an b, hence ν a = ν b. Thus option (a) is current. 4 4 10. + He Z Z 4 4 Z ZC + e Hence, an C are isotopes. 1 S 11. = S 91Ω 1100 100 S 100S + 1000 + 100 + S
Q 1. a q = l 1 q V = v = V 4πε x 0 4 R 4 R ρ ρ π π 1. V = 4πε0x R 4πε0 x 14. In p-n junction, the iffusion of majority carriers ominates when junction is forwar biase an rifting of minority carriers ominates across the junction, when it is reverse biase. α 0.9 15. β = = = 9 1 α 1 0.9 IC IC = = IC = 18µ I µ 16. Q, S, C Q, D P 17. Work one = force istance W = area enclose by F-x curve From the given figure, W = + = 1.5J. 18. (b) s intensity is maximum at axis, µ will be maximum an spee will be minimum on the axis of the beam. beam will converge. 19. () For a parallel cylinrical beam, wavefront will be planar. 0. (a) 1. a t t. r t t ω t a t = t = r = t t t ω = ω = 0 0 a = rω n n 0 0 n g.s = 4πG(m ) m = ρ r (4πr )r. Given, t = ax + bx t x x Differentiating w.r.t. to = ax + b t t t x 1 v = = t (ax + b) x a x gain ifferentiating, w.r.t. = t (ax + b) t x a f = = t (ax + b) (ax + b) γ + + + + + + + + + + + + + + + + x=0 x=1 x a or f = f = av (ax + b) 4. Work one by conservative force oes not epen on the path. Electrostatic force is a conservative force.
5. = RhT + RhR 6. TV γ 1 = constant RT γrt v rms = ; vsoun = M M 7. s iffraction pattern has to be wier than slit with, so () is the correct option. 8. Electric fiel at a istance r from is I E = ρ V = E r πr V V = V C a b a r 1 1 = V = π r π a a + b 9. From E = ρ J = π r hfe 0. For a transistor amplifier in common emitter configuration, current gain i =, where h fe 1 + hoer L an h oe are hybri parameters of a transistor. 50 i = = 48.78 6 1+ 5 10 1 10