CLASS xi scHENCE PHYSICS PRE-BoaRD EXAM 2019 (ser 8) F.M: 70 GENERAL INSTRUCTIONS: TIME: 3 HRS a} Ail questions are compulsory. yery short answer type carrying b) There are 27 questioas in total. Question numbers 1 to 5 are ‘one mark each. Question numbers 6 to 12 are short answer type carving two marks each, Question numbers 13 to 24 carry three marks each. Question numbers 25 to 27 carry five marks each. There is a0 overall choice. However, an internal choice has been provided In two questions of 1 mark, two questions of 2 marks, 3 questions of 3 marks, and all the questions of 5 marks. ) Use of calculator is not permitted. a SECTION A 1, Define electric susceptibility. Give its dimension, (% + 4) 2. Aholiow metal sphere of radius 3cm is charged such that the potential on its surface is 10V. What is the potentiat at the centre of the sphere? Fora given spherical shel give the graphical variation of electric potential with distance r from the centre. (¥: + %) 3. Nichrome and copper wires of same length and area of cross section are connected in series, current is passed through them. Why does the nichrome wire gets lieated first? OR When a potential difference is applied across, determine the current passing through (a) a semiconductor at Ok (b) a metal at OK. ™, 4, Work function of At is 4.2 eV. If two photons each of energy 2.5 eV are incident on its surface, will the emission of electrons take place? Justify. 5. The KE of a particle incident on a gold foil is doubled. How does the distance of closest ‘auproach change? ‘ on = Two nuclei have mass numbers in the ratio 2:5. What is the ratio of their nuclear densities?SECTION 0 ‘6. sketch and label the eneray bard dagram for p type semiconductor ithe energy ot photon of sour IBN (Wavelength » S891m) exuals the band gap of a wemivonsveror, ctcuate the rvirun eM required in fro te hole electron pal. (1+) oR ae using NOR gate, Draw the output waveform from the given set up. (1+1) / 9, Two towers on the top 0 « fl halfway between the toSECTION ¢ 413, State Gauss’s Law in. electros: Given the electric field in the regi M region E = 2xj Jt electric flux through the cube and th charge enclosed by it. ‘a : me 2 Am oo & 14, (a) Find equivalent capacitance between A and B in the combina"! 1 below, each capacitor is of 2uF capacitance (0) Ifa DC source of 7V is connected across AB, how much charge is drawn from the source and what in the energy stored in the network? 15. Define relaxation time of the free electrons drifting in a conductor. How is it related to the drift velocity of free electrons? Two cells of E; and E, are connected as shown, resistance of 0,30 and 1.20. Calculate (a) the value of curren! across 60 resistance. [1+2] Ey cL | rt bX BL and have an e.m.f 5V and 9V and internal it through 30 (b) power dissipated 4-5 16. The resistances in the two arms of the meter bridgé are 59 and R&2. Wien the resistance Ris shunted with an equal resistance, the new balance point is at 1.6L:. Determine the resistance R. Way are the connecting resistors in a meter bridge made of thick copper strips? [2+1] 5a RD ald woh O OR Define temperature coefficient of resistivity. ‘Arichrome heating element connected to a 220V supply draws an initial current settles down after a few seconds to a steady value of 2A, Find the steady temperature of the heating element. The room temperature Is 30°C aNd Cujo 3.710% °C2. [142] of 2.2A whichV7. 18. 19. 20. raw the diagrams to show the behavior f Magnetic ld tines near a bar of) copper (b) mae erature. aluminum (c) mercury, at a very low ie an ‘A small compass needle of magnetic mo Mis fee o tury abc UC Sa ge the direction of uniform magnetic eld B. The moment of inertia of the needle about the axis is 1. The needle is slightly disturbed from Its t#ble position and then released. Prove that it executes SHM. [1.5 + 1.5] ‘OR Name the physical quantity with unit Am. Is ita scalar or vect magnetic dipote is under the influence of two magnetic fields. The anple between the field directions is 60 degrees and one of the fields has a magnitude of 1.210". If the dipole comes to stable equilibrium at an angle of 15 degrees with this field, what is the magnitude of the other field? [142] ° Draw the block diagram of a detector for an amplitude modulated wave. What should be the height of a transmitting antenna if the TV telecast is to cover a radius of 128Km. How much of the population will be covered, if the population density is 1000Km7? [242] Write down the working principle of optical fibres. The figure shows a ray of light falling normally on the face AB of an equilateral glass prism having r.i 3/2 placed in water of r.i 4/3 . ‘will this ray suffer total internal relieep on striking the face AC? Justify your answer. OR fe me i Define resolving power of a telescope. Write the two factors on which il iepends. Ajar of height ")) ‘nis filled with a liquid of rip. At the center of the jar on the bottom is a dct. Find the minimum iameter ofa disc, such that whem It)siplaced on the top surface , the dot is invisible. fled ieee Waine the constituent radiations of em specrrum, used for the following purposes {n satellite communication, for studying cr ‘ture, is used to detect leakage of oil in i stal structure, underground pipelines, is absorbed ee Brice by ozone layer, to improve visibility during fog and mist, produces intense h t21, A coll of N number of turns Magnetic Meld B and connected ce roeated ate constant angular spee\t vIn a unitorn and power dissipation in the coil stor w, peduce expression for Maximum emf in the colt ies a 2 pee a the average power consumed in ay inductor! t cay i 4 ir ary nduetor Leonnected £0 an We source Is rer0, In 9 : Nt, Xve R, and the power factoy of the clfelt 1 Py. When a capacitor wit ; pacitance C such that Xo= Xs put in seriee ae eager factor L Tind PsP Series, tha power factor becomes P, Find Py/P, 2 . From the given plot, answer the following ‘twa y 9 V Q i 2 ; + ae 0 om, Dxiolt He (i), Which one of the two metals has higher threshold frequency ? (ii) Determine the work function of the metal which has greater velue (ill) Find the maximum KE of electron emitted by light of frequency § x 10 “iz for this metal, (ayaa) surface of negligible work 24, If an em wave of wavelength J is incident on a photosensitive st Ae (2me/h)Ar. function. if the photoelectrons emitted are having wavelength of Ax, prove that erating potential required to accelerate a proton and an a particle to Calculate the ratio of accel (2441) have the same de Broglie wavelength associated with them. OR KE carried by a particle in a decay is{ (A~4)/AJQ. where Q Is the total U*js 4,5 x 10° years. What is the activity of 18 (2#1) Show that the energy released in the decay. The half life of sa of sample of »2U**? SECTION D 25. Describe the principie, construction and working of moving coil galvanometer. Define its figure of merit. [441] OR State the vector form of Biot-Savart Law: State two differences between static field and magnetic field. Determine the magnetic field due to along straight current carrying conductor {1+1+3) 26. State the difference between wo! in reverse bias? (3+2] rking of a ore diode and LED. Why isa photo diode operated oOR With the help of a labeled circuit diagram, Plain the use uf ny.» wansistor asa CE amplifier. Discuss the phase relastonship between INPUt and output voltages, and compare it with the CB ‘configuration. [2+2+1] P 27, Consider two coherent sources S; and $2 Producing monochromatic wa ves to produce interference pattern . Let the displacement of the wave produced by 5,be given by yi= a cos wt, and that for S is given by yo= a cos (wt +9). ~ Jout the expression for the amplitude of the resultant displacement at a point and show that point will be | = 42’cos"9/2, Hence establish the conditions for interference. would have changed continuously with time, what would have been the ‘ a (24241) aaa a B.D.M INTERNATIONAL EXAMINATION PRE BOARD I SUBJECT: PHYSICS SUBJECT CODE® 042 XII (SESSION 2023-24) set: B CLAS Maxim Time allowed: General Instructions: e are 33 questions in all. All questions are compulsory. question paper has five sections: Scetion A, Section B , Section C , Section D and ich, Section B contains five questions of Section D three long {iii)Section A contains sixteen MCQ of 1 mark two marks each, Section C contains seven questions of three marks exch s two case study based questions of 4 marks each and Section F cont questions of five marks each. (iv) There is no overall choice, However, an internal choice has been provided B, and Section C, in two questions of Section D and in section E all questions have internal choice. You have to attempt only one of the choiees in such ques (v) Use of calculator is not allowed. SECTION A ‘An electron initially at rest , is accelerated through a potential difference of 200 V, so that it acquires a velocity 8.4 x 10° m/s. The value of em of electron will be a) 1.76x 10" C/kg —b) 2.76x 10 C/kg —¢) 0.76 x 10" C/kg_—_d) none of these What is the effective capacitance between X and Y? cya (a)24 nC (b)18 pC (12 pe (a) 6 nC Given n resistors each of resistance R what is the ratio of maximum to minimum resistance? a) I/n? byl ©) Wn awit ‘The wire loop PQRSP formed by joining two semi-circular wires of radii Ry and Roy carries a current I as shown. The magnitude of the magnetic induction at the centre Cis —— =~ —— Page 1/9