fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Solid State Physics, Devices and Electronics IIT-JAM 2005 Q1. A circuit and the signal applied at its input terminals ( Vi ) are shown in figure below. Which one of the options correctly describes the output waveform ( V0 ). (Assume all the devices used are ideal). 2V C Vi t 0 D Vo 2V (a) 2V 0 (c) (b) 0 t 2V 2V 4V (d) 0 t 0 t t - 4V Ans. : (c) Solution: Its clamper circuit in which peak to peak remains fixed and voltage level will shift in the direction of diode current. Q2. The susceptibility of a diamagnetic material is (a) positive and proportional to temperature (b) negative and inversely proportional to temperature (c) negative and independent of temperature (d) positive and inversely proportional to temperature Ans. : (b) H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 1 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q3. Which of the following statements is correct for NaCl crystal structure? (a) It is simple cubic lattice with one atom basis (b) It is a face-centered cubic lattice with one atom basis (c) It is a simple cubic lattice with two atom basis (d) It is a face-centered cubic lattice with two atom basis Ans. : (d) IIT-JAM 2006 Q4. In a crystalline solid, the energy band structure ( E - k relation) for an electron of mass m is given by E 2 k 2k 3 . The effective mass of the electron in the crystal is 2m (a) m (b) 2 m 3 (c) m 2 (d) 2m Ans. : (c) Solution: The expression of effective mass of electron in solid is m * 2 d 2E 2 dk m dE 2 d 2 E 2 2 2 m* 4 k 3 4 2 2 dk 2m dk 2m m Q5. The truth table for the given circuit is J Q K (a) (c) J 0 0 1 1 K 0 1 0 1 Q 1 0 1 0 J 0 0 1 1 K 0 1 0 1 Q 0 1 0 1 (b) (d) J 0 0 1 1 K 0 1 0 1 Q 1 0 0 1 J 0 0 1 1 K 0 1 0 1 Q 0 1 1 0 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 2 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Ans. : (c) Solution: Q J .K J .K K Q6. In an intrinsic semiconductor, the free carrier concentration n (in cm 3 ) varies with temperature 36.5 T (in Kelvin) as shown in the figure below. The band gap of the semiconductor is (use Boltzmann constant k B 8.625 105 eVK 1 ) 35.5 lnn 34.5 33.5 (a) 1.44 eV 32.5 (b) 0.72 eV (c) 1.38 eV 2 3 1000 / (d) 0.69 eV Ans. : (d) Eg 1 1 E n Solution: Since ni n N c N v exp g 1 exp n2 2kT 2k T2 T1 n 1 1 Eg 2k ln 1 2 8.625 105 36.5 32.5 0.003 0.0002 n2 T2 T1 Eg 2 8.625 105 4 1103 0.69eV IIT-JAM 2007 Q7. Fermi energy of a certain metal M 1 is 5eV . A second metal M 2 has an electron which is 6 % higher than that of M 1 . Assuming that the free electron theory is valid for both the metals, the Fermi energy of M 2 is closet to (a) 5.6 eV (b) 5.2 eV (c) 4.8eV (d) 4.4 eV Ans. : (b) Solution: The expression of Fermi energy is E F 2 3 2 n 2m 2/3 Let us consider that n1 , E F1 is the concentration of electron and Fermi energy in metal M1 and n2 , E F2 is in metal M2. H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 3 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Given, n 2 n1 0.06n1 1.06n1 2 3 2 n2 EF2 2m EF1 2 3 2 n1 2 m 2/3 2/3 n2 1.06n1 1.06 2/3 1.0396 2/3 2/3 2/3 n1 n1 2/3 EF2 1.0396 EF1 1.0396 5eV 5.2 eV Q8. Fig. (i) Fig. (ii) Figure (i) and (ii) represent respectively, (a) NOR, NOR (b) NOR, NAND (c) NAND, NAND (d) OR, NAND Ans. : (c) IIT-JAM 2008 Q9. The ratio of the second-neighbour distance to the nearest-neighbour distance in an fcc lattice is (a) 2 2 (b) 2 (c) 3 (d) 2 Ans. : (d) Solution: In FCC lattice the first nearest is at distance 2a / 2 a / 2 Whereas the second nearest at distance of a The ratio of the second-neighbour distance to the nearest-neighbour distance is a a/ 2 Q10. 2 Consider a doped semiconductor having the electron and the hole mobilities n and p , respectively. Its intrinsic carrier density is ni . The hole concentration p for which the conductivity is minimum at a given temperature is (a) ni n p (b) ni p n (c) ni p n (d) ni n p H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 4 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Ans. : (a) n2 Solution: Conductivity e nn p p e i n p p p For minimum conductivity, Q11. d 0 p ni n / p dp The logic expression for the output Y of the following circuit is P Y Q R S (a) P Q QR S (b) P Q QR S (c) P Q QR S (d) P Q QR S Ans. : (a) Solution: P PQ P Q QR P Q QR S Y Q R P Q QR S QR S H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 5 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics IIT-JAM 2009 0 Q12. Monochromatic X -rays of wavelength 1A are incident on a simple cubic crystal. The first order Bragg reflection from 311 plane occurs at angle of 30 0 from the plane. The 0 lattice parameter of the crystal in A is (a) 1 (b) 3 (c) 11 2 (d) 11 Ans. : (d) Solution: Expression of Bragg´s law is 2d sin n , where, d is the inter-planar spacing defined for cubic lattice of lattice constant a in term a of Miller indices h k l as d h2 k 2 l 2 The lattice parameter a is a Q13. 2 sin h2 k 2 l 2 1 1 3 2 12 12 11 11 0 2 1/ 2 2 sin 30 Which one of the following is an INCORRECT Boolean expression? (a) P Q PQ Q (b) P Q P Q P (c) PP Q Q (d) P Q R P Q R PQ R PQ R Q Ans. : (c) Solution: (a) PQ PQ P P Q 1.Q Q (b) P Q P Q P QQ P (c) P P Q P PQ P 1 Q P (d) PQR PQR PQR PQR PQ R R PQ R R PQ PQ P P Q Q Q14. A battery with a constant emf and internal resistance ri provides power to an external circuit with a load resistance made up by combining resistance RL and 2 RL in parallel. For what value of RL will the power delivered to the load be maximum? (a) R L ri 4 (b) RL ri 2 (c) RL 2 ri 3 (d) RL 3 ri 2 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 6 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Ans. : (d) Solution: Since RL and 2 RL are in parallel so load R RL 2 RL 2 RL . RL 2 RL 3 2 Power through load P I R R ri R 2 For maximum power through load r R 2 2 R 2 ri R 0 r R 2 R 0 R r dP 0 i i i 4 dR ri R 2 Thus R ri 2 3 RL ri RL ri 3 2 IIT-JAM 2010 Q15. The following are the plots of the temperature dependence of the magnetic susceptibility for three different samples. a (T ) b (T ) 0 T 0 T c (T ) 0 T The plots a, b and c correspond to (a) ferromagnet, paramagnet and diamagnet, respectively (b) paramagnet, diamagnet and ferromagnet, respectively (c) ferromagnet, diamagnet and paramagnet, respectively (d) diamagnet, paramagnet and ferromagnet, respectively Ans. : (b) 0 Q16. The value of at which the first-order peak in X -ray ( 1.53A ) diffraction corresponding to 111 plane of a simple cubic structure with the lattice constant, 0 2.65 A , is approximately (a) 150 (b) 300 (c) 450 (d) 600 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 7 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Ans. : (b) Solution: Expression of Bragg´s law is, 2d sin n where, d is the inter-planar spacing defined for cubic lattice of lattice constant a in term of Miller indices (h k l) as d sin Q17. 2d 2a h2 k 2 l 2 a h2 k 2 l 2 1.53 1 1 3 sin 1 300 2 2.65 2 2 Consider the following truth table The logic expression for F is (a) AB BC CA (b) A B AC B C (c) CA B AB (d) C A B AB A B C F 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 1 0 0 0 1 1 1 0 Ans. : (d) C 1 Solution: F AB C A B C 0 1 A B 00 A B 01 AC 1 AB 11 AB 10 1 1 AB BC H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 8 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics IIT-JAM 2011 Q18. An X - ray diffraction XRD experiment is carried out on a crystalline solid having FCC structure at room temperature. The solid undergoes a phase transformation on cooling to 200 C and shows orthorhombic structure with small decrease in its unit cell lengths as compared to the FCC unit cell lengths. As a result the 311 line of the XRD pattern corresponding to the FCC system (a) will split into a doublet (b) will split into a triplet (c) will remain unchanged (d) will split into two separate doublets Ans. : (b) Solution: In FCC the inter-planar spacing is defined as d a h2 k 2 l 2 whereas in Orthorhombic the inter-planar spacing is d 1 2 h k2 l2 a2 b2 c2 For 311 , numbers XRD peaks in FCC is derived from Bragg’s law as sin 2d 2a h2 k 2 l 2 2a 3 2 12 12 2a 11 Thus only one peak appears in FCC. In Orthorhombic, sin 2d 2 h2 k 2 l 2 a2 b2 c2 For 311 , there will be three peaks corresponding to , sin 1 and sin 1 1 sin 1 2 3 12 32 12 12 12 32 32 12 12 2 2 2 2 2 2 2 2 2 2 2 2 a b c a b c a b c H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 9 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q19. Which of the following circuit does not satisfy the Boolean expression AB A B F (a) (b) F (c) F (d) F F Ans. : (d) Solution: (a) F AB AB (b) F A B . AB A B . A B AB AB (c) F A B . A B AB AB (d) F AB AB IIT-JAM 2012 0 Q20. An X -ray beam of wavelength 1.54 A is diffracted from the 110 planes of a solid with 0 a cubic lattice of lattice constant 3.08 A . The first-order Bragg diffraction occurs at 1 (b) sin 1 2 2 1 (a) sin 1 4 1 (c) sin 1 2 1 (d) sin 1 2 Ans. : (b) Solution: Expression of Bragg´s law is 2d sin n where, d is the inter-planar spacing defined for cubic lattice of lattice constant a in term of Miller indices ( h k l ) as d sin 2d 2a h2 k 2 l 2 a h2 k 2 l 2 1.54 1 1 2 sin 1 2 3.08 2 2 2 2 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 10 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q21. The Boolean expression P P Q , where P and Q are the inputs to a circuit, represents the following logic gate (a) AND (b) NAND (c) NOT (d) OR Ans. : (d) Solution: P Q PQ P PQ 0 0 0 0 0 1 1 1 1 0 0 1 1 1 0 1 IIT-JAM 2013 Q22. The fraction of volume unoccupied in the unit cell of the body centered cubic lattice is (a) 8 3 8 (b) 3 8 (c) 6 2 6 (d) 3 2 Ans. : (a) Solution: The effective number of atoms in bcc structure is 1 1 1 1 neff nc n f ni 8 0 1 2 8 2 8 2 E F The radius of atom and lattice constant are related as a a 3 r 4 a The volume occupide by the atoms in unit cell is 4 2 3 G D a C 3 a 3 3 3 a 8 4 Thus amount of volume unoccupied in the unit cell is volume of unit cell filled volume a 3 8 3 3 a 3 a 8 8 3 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 11 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Thus, the fraction of volume unoccupied in the unit cell of the body centered cubic lattice 8 3 is 8 Q23. For an ideal op-amp circuit given below, the dc gain 1 k and the cut off frequency respectively are 1 F 2 (a) 1 and 1kHz (b) 1 and 100 Hz 1 k (c) 11 and 1kHz 10 k (d) 11 and 100 Hz Ans. : (b) 10 1 1 11 and f H 1kHz 1 2 RC 2 1 1 2 A variable power supply 5V 20V is connected to a Zener diode specified by a Solution: DC Gain 1 Q24. breakdown voltage of 10V (see figure). The ratio of the maximum power to the minimum power dissipated across the load resistor is 500 5V 20 V 1 k Ans. : 9.02 Solution: When V 5V open circuit voltage Vi VL Vi 3.33V PL ,min 1000 5 3.33 VZ 10V 1500 Vi 2 . RL When V 20V open circuit voltage Vi 1000 20 13.33 VZ 10V 1500 2 VL V z 10V PL ,max P V2 V 2 10 Z L ,max Z2 9.02 RL PL ,min Vi 3.33 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 12 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics IIT-JAM 2014 Q25. Octal equivalent of decimal number 478 10 is (a) 736 8 (b) 6738 (c) 637 8 (d) 367 8 Ans. : (a) Solution: 7368 7 82 3 81 6 80 448 24 6 47810 6738 6 82 7 81 3 80 384 56 3 44310 6378 6 82 3 81 7 80 384 24 7 41510 3678 3 82 6 81 7 80 192 48 7 24710 Q26. In an ideal operational amplifier depicted below, the potential at node A is 5 k A 25 k _ 5V IV (a) 1V (b) 0V (c) 5V (d) 25V Ans. : (b) Solution: Node A is virtually grounded. Q27. To operate a npn transistor in active region, its emitter-base and collector- base junction respectively, should be (a) forward biased and reversed biased (b) forward biased and forward biased (c) reversed biased and forward biased (d) reversed biased and reversed biased Ans. : (a) Solution: In active region: emitter-base junction is F.B. : collector-base junction is R.B. H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 13 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q28. Diamond lattice can be considered as a combination of two fcc lattice displaced along the body diagonal by one quarter of its length. There are eight atoms per unit cell. The packing fraction of the diamond structure is (b) 0.74 (a) 0.48 Ans. : (c) Solution: P F (c) 0.34 (d) 0.68 4 3 r 3 V neff Where, neff 8, V a 3 and 3a 8r 2r a 4 3 4 3 r 3 3 PF 0.34 . 3 16 8r 3 Thermal neutrons (energy 300 , k B 0.025 eV ) are sometimes used for structural 8 Q29. determination of materials. The typical lattice spacing of a material for which these can be used is (a) 0.01nm (b) 0.05 nm (c) 0.1 nm (d) 0.15 nm Ans. : (c) Q30. A sine wave of 5V amplitude is applied at the input of the Vin Vout 1 k circuit shown in the figure. Which of the following waveforms represents the output most closely? 5V 5V (a) 3V (b) -3V -5V (c) 3V (d) 3V -3V -5V Ans. : (d) Solution: If Vin 3 V , diode is OFF and V0 Vin . If Vin 3 V , diode is ON and V0 3 V . H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 14 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q31. 1011 binary input have been applied at X 3 X 2 X 1 X 0 input in the shown logic circuit made of XOR gates. The binary output Y3Y2Y1Y0 of the circuit will be X3 Y3 (a) 1101 X2 Y2 X1 Y1 X0 Y0 (c) 1111 (b) 1010 (d) 0101 Ans. : (a) Solution: 1 X3 Y3 1 0 X2 Y2 1 1 X1 Y1 0 1 Y0 1 X0 IIT-JAM 2015 Q32. Temperature dependence of resistivity of a metal can be described by (a) (b) R R T T (c) R (d) T R T H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 15 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Ans. : (a) Solution: Electrical resistivity of metal varies as T5 (For T D ) T (For T D ) where D is the Debye temperature. Thus, correct answer is option (a) Q33. A Zener regulator has an input voltage in the range 15V 20V and a load current in the range of 5 mA 20 mA . If the Zener voltage is 6.8V , the value of the series resistor RS should be V0 15 20 V (a) 390 6 .8 V (b) 420 (c) 440 (d) 460 Ans. : Some data is missing. (No answer is possible) Q34. Which of the following circuits represent the Boolean expression S P QR Q P (a) P Q (b) P Q S (c) P Q R S (d) P Q S R S H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 16 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Ans. : (b) Solution: S P QR QP P QR QP P QR QP PQ (a) P Q (c) P Q S PQ P Q (b) P Q (d) PQ S P Q R R S PQ P Q PQ S PQR R R Q35. R Miller indicates of a plane in cubic structure that contains all the directions 100, 011 and 111 are (a) 011 (b) 101 (c) 100 (d) 110 Ans. : (a) y Solution: The name of the plane containing all the directions 111 100 , 011 & 111 is 0 11 or 01 1 The best suitable answer is option (a) 011 x 100 z Q36. In an ideal Op-Amp circuit shown below R1 3k , R2 1k and Vi 0.5sin t (in Volt). Which of the following statements are true? V i (a) The current through R1 The current through R2 (b) The potential at P is V0 R2 R1 V0 P R2 R1 (c) The amplitude of V0 is 2V (d) The output voltage V0 is in phase with Vi Ans. : (a), (c) and (d) H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 17 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Solution: Voltage at P is VP V0 R2 . R1 R2 Current through R1 is I1 Vo VP R1 and Current through R2 is I 2 Vo V0 R2 V0 R1 V0 R1 R2 R1 R1 R1 R2 R1 R2 V0 VP . R2 R1 R2 Thus I1 I 2 . Option (a) is true The potential at P is VP V0 R2 . Option (b) is not true. R1 R2 R 3 V0 1 2 Vi 1 0.5sin t 2sin t Vm 2 V . Option (c) is true R1 1 Option (d) is true Q37. In the given circuit VCC 10V and 100 for n p n transistor. The collector voltage VCC VC (in volts) is…………. 1K 100 K VC 5V Ans. : 5.7 Solution: I B 5 0.7 4.3 105 A I C I B 4.3 mA 3 100 10 VC VCC I C RC 10 4.3 5.7 V Q38. A diode at room temperature kT 0.025 eV with a current of 1A has a forward bias voltage V F 0.4V . For V F 0.5V , the value of the diode current (in A ) is………….. Ans. : 54.5 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 18 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Solution: I I 0 e V / VT Q39. V2 / VT 1 e0.5/ 0.025 1 e 20 1 I2 e 1 V / V 54.5 I 2 54.5 A I1 e 1 T 1 e0.4 / 0.025 1 e16 1 GaAs has a diamond structure. The number of Ga-As bonds per atom which have to be broken to fracture the crystal in the 001 plane is……….. Ans. : 4 Solution: Diamond structure has tetrahedral bond. To fracture the diamond structure along 0 0 1 plane, four bonds need to be broken. IIT-JAM 2016 Q40. The solution of the Boolean equation Y A B AB is (b) AB (a) 1 (c) A B (d) A B Ans. : (b) and (d) both are correct Solution: Y A B AB A.B A B A 1 B B A B or AB Q41. If a constant voltage V is applied to the input of the following OPAMP circuit for a time t , then the output voltage V0 will approach C R V Vo (a) V exponentially (b) V exponentially (c) V linearly (d) V linearly Ans. : (d) Solution: I R I C d 0 V0 dV V V V 0 0 V0 t c C dt RC RC R dt H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 19 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q42. A pn junction was formed with a heavily doped 1018 cm 3 p -region and lightly doped 10 14 cm 3 n - region. Which of the following statement s is (are) correct? (a) The width of the depletion layer will be more in the n - side of the junction (b) The width of the depletion layer will be more in the p - side of the junction (c) The width of the depletion layer will be same on the both side of the junction (d) If the pn junction is reverse biased, then the width of the depletion region increase Ans. : (a), (d) Solution: Since p - region is heavily doped and n - region is lightly doped, on n - side width of depletion layer will be more and on p - side width of the depletion layer will be less. Q43. The addition of two binary numbers 1000.01 and 0001.11 in binary representation is…………. Ans. : 1010 Solution: 1000.01 0001.11 1001.00 Q44. The number of second-nearest neighbor ions to a Na + ion in NaCl crystal is__________. Ans. : 12 Solution: The 2nd nearest neighbour is at distance The number of 2nd nearest neighbour Q45. 2a a 2 2 Cl Na 3 8 12 2 The output voltage V0 of the OPAMP circuit given below is…………….. V 2R 1V 2V 3V R R Vo R R H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 20 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Ans. : 6 2R 2R Solution: V0 1 V1 3V1 R R/2 R/2 R/2 1 2 3 Where, V1 R R/2 R R/2 RR/2 1V 2V 3V 1 1 1 V1 1 2 3 2V V0 6 V 3 3 3 Q46. R R V0 R R In the circuit given below, the collector to emitter voltage VCE is…………… V . (Neglect VBE , take 100 ) VCC 10 V 5k 5k VCE 5k 10 k Ans. : 2.5 Solution: VB V 5 5 10 5 V VE VB VBE 5 V I E E 0.5 mA 55 RE 10 VCE VCC I C RC RE 10 0.5 5 10 2.5 V Q47. X -ray diffraction of a cubic crystal gives an intensity maximum for Bragg angle 200 corresponding to the 110 plane. The lattice parameter of the crystal is………….. nm . (Consider wavelength of X ray 0.15 nm ) Ans. : 0.31 Solution: According to Bragg’s law 2d sin n 0.5 109 0.15 109 For n 1 , 2d sin d d 0.219 nm 2sin 2 sin 200 2 0.342 a a Now, d 2 h2 k 2 l 2 a 2 d 0.31 nm a 0.31 nm H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 21 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics IIT-JAM 2017 Q48. Consider the following circuit with two identical Si diodes. The input ac voltage waveform has the peak voltage VP 2V , as shown R P Vin D1 2V D2 R t Q The voltage waveform across PQ will be represented by: VPQ VPQ (a) (b) t t VPQ (c) VPQ (d) t t Ans. : (c) Solution: R P Vin D1 2V D2 R t Q During positive half cycle D1 is ON, when input is more than 0.7V and D1 is OFF when input is less than 0.7V. During negative half cycle D1 is ON, when input is more negative than 0.7 IR and D1 is OFF when input is less negative than 0.7 IR . Q49. If the Boolean function Z PQ PQR PQRS PQRST PQRSTU , then Z is (a) PQ R S T U (c) P Q (b) P Q (d) P Q R S T U H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 22 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Ans. : (c) Solution: Z PQ PQR PQRS PQRST PQRSTU PQ PQR PQRS PQRST 1 U PQ PQR PQRS PQRST PQ PQR PQRS 1 T PQ PQR PQRS PQ PQR 1 S PQ PQR PQ 1 R PQ Z PQ P Q Q50. Shown in the figure is a combination of logic gates. The output values at P and Q are correctly represented by which of the following? 1 P Q 0 (a) 0 0 (b) 1 1 (c) 0 1 (d) 1 0 Ans. : (c) 1 Solution: P 0 1 0 Q 1 0 Q51. A plane in a cubic lattice makes intercepts of a, 2a a with the three and 3 2 crystallographic axes, respectively. The Miller indices for this plane are: (a) 2 43 (b) 34 2 (c) 634 (d) 123 Ans. : (a) Solution: Intercepts: a, Divide by a : 1, Reciprocal: 1, 2, LCM: 2, 4, 2a 3 2 3 3 2 3 Miller Indices = 2 4 3 a , 2 1 , 2 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 23 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q52. Which one of the following schematic curves best represents the variation of conductivity of a metal with temperature T ? (a) (b) 0 (c) T (d) 0 T 0 T 0 T Ans. : (b) Solution: Resistivity of metal is 0 ph , where 0 is temperature independent And, ph T 5 when T D and ph T when T D The conductivity is defined as 1 S 0 T T Thus correct option is (b) Q53. KCl has the NaCl type structure which is fcc with two-atom basis, one at 0, 0, 0 and the other at 1/ 2,1/ 2,1/ 2 . Assume that the atomic form factors of K and Cl are identical. In an X - ray diffraction experiment on KCl , which of the following h k l peaks will be observed? (a) 10 0 (b) 110 (c) 111 (d) 2 0 0 Ans. : (d) Solution In KCl the reflection from 111 layer containing K ions is exactly out of phase with the reflection from the Cl close packed layers. The net effect is that the two reflections cancel and 111 is absent. This mean the first reflection is from 200 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 24 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q54. An n p n transistor is connected in a circuit as shown 6V in the figure. If I C 1 mA, 50,VBE 0.7 V and the current through R2 is 10 I B where, I B is the base current. R1 2.5 k Then the ratio R1 / R2 is: VC (a) 0.375 VCE 3V (b) 0.25 VE 0.5V R2 (c) 0.5 0.5k (d) 0.275 Ans. : (b) Solution: I1 I i I 2 I 2 10 I B , I C 1 mA, 50,VBE 0.7 V VB I 2 R2 VBE I E RE 0.7 0.5 1.2 V 6V R1 1.2 V 1.2 V 1.2 V R2 6 k I2 10 I B 10 1/ 50 V R 6 6 R1 24 k VB CC 2 1.2 R1 R2 R1 6 Q55. 6V I1 2.5 k C VC Ii VCE 3V B R2 I2 VE 0.5V E 0.5k R2 6 0.25 R1 24 An intrinsic semiconductor of band gap 1.25eV has an electron concentration 1010 cm 3 at 300 K . Assume that its band gap is independent of temperature and that the electron concentration depends only exponentially on the temperature. If the electron concentration at 200 K is Y 10 N cm 3 1 Y 10; N integer , then the value of N is………… Ans. : 4 Solution: ni N c N v e Eg / 2 kT E / 2 kT Eg 1 ni1 e g 1 1010 cm 3 1 Eg / 2 kT2 exp ni 2 e ni 2 2k 300 200 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 25 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Eg 1 1.25 1.6 1019 1 1 10 10 6 10 exp ni 2 1010 exp 10 5.7 10 23 2 1.38 10 100 6 2k 300 200 4 3 ni 2 5.7 10 cm N 4 Q56. An OPAMP is connected in a circuit with a Zener diode as shown in the figure. The value of resistance R in k for obtaining a regulated output V0 9V is………….. 1k (Specify your answer to two digits after the decimal point) R 1k Vin 12 V Vo VZ 4.7 V Ans. : 1.09 1 Solution: V0 1 4.7 9V R 1.09k R IIT-JAM 2018 Q57. Which one of the following graphs shows the correct variation of V0 with Vi ? Here, Vd is the voltage drop across the diode and the OP-Amp is assumed to be ideal. V0 (a) Vi Vd V0 RL V0 (b) Vi 0 0 Vd Vi V0 V0 (c) (d) 0 Vd Vi 0 Vi Ans. : (a) Solution: During positive half cycle it behaves as voltage follower i.e. v0 vi , during negative half cycle v0 0 . H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 26 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q58. The Boolean expression AB A B A B can be simplified to (a) A B (b) AB (c) A B (d) AB Ans.: (c) Solution: Y AB AB A B AB AB AB A B AB AB AB AB AB A B Q59. In a pn junction, dopant concentration on the p -side is higher than that on the n -side. Which of the following statements is (are) correct, when the junction is unbiased? (a) The width of the depletion layer is larger on the n -side. (b) At thermal equilibrium the Fermi energy is higher on the p -side. (c) In the depletion region, number of negative charges per unit area on the p -side is equal to number of positive charges per unit area on the n -side (d) The value of the built-in potential barrier depends on the dopant concentration. Ans. : (a), (c) and (d) Q60. Which of the combinations of crystal structure and their coordination number is (are) correct? (a) body centered cubic 8 (b) face centred cubic 6 (c) diamond 4 (d) hexagonal closed packed 12 Ans. : (a), (c), (d) Solution: Co-ordination number in different crystal structure are (i) Body central cubic 8 (ii) Face central cubic 12 (iii) Diamond 4 (iv) Hexagonal closed packed 12 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 27 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q61. For the given circuit, value of the base current I b of the npn transistor will be ____mA. ( is the current gain and assume Op-Amp as ideal.) (Specific your answer in mA upto two digits after the decimal point.) 10V 1k 5V Ib 50 1k Ans. : 0.1 10V Solution: v2 5V VE IE 1k 5V 5 5 mA 1 I B 5 mA I B Q62. 5 mA 0.1 mA 50 v1 v 2 Ib E 50 I E 1k The lattice constant of unit cell of NaCl crystal is 0.563 nm . X -rays of wavelength 0.141 nm are diffracted by this crystal. The angle at which the first order maximum occurs is _______degrees. Ans. : 12.5 Solution: 2d sin 3 1 sin 2d 2a sin 1 3 0.141 1 0 sin 1 sin 0.217 12.53 2 0.563 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 28 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q63. For the following circuit, the collector voltage with respect to ground will be _________ V . (Emitter diode voltage is 0.7V and DC of the transistor is large) (Specify your answer in volts upto one digit after the decimal point). 10V 3k 3k 1k Ans. : 3.1 3V Solution: VBE 0.7 V and dc large so I B 0 10V From input section; 3k C 0 0.7 I E 1 3 0 B I E 2.3 mA From output section; IB 0 10 3 2.3 VC 0 3k VC 10 6.9 3.1V Q64. E 1k 3V In the following circuit, the time constant RC is much greater than the period of the input signal. Assume diode as ideal and resistance R to be large. The dc output voltage across resistance R will be ____________ V . (Specify your answer in volts upto one digit after the decimal point) C 24Vrms C R Ans. : 68 Solution: It’s a voltage doubler circuit VR 2Vm 2 2 Vrms 2 2 24 VR 68 V H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 29 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q65. For a metal, the electron density is 6.4 1028 m 3 . The Fermi energy is __________ eV . ( h 6.626 1034 J s, me 9.111031 kg , 1 eV 1.6 1019 J ) (Specify your answer in electron volts eV upto one digit after the decimal point) Ans. : 5.84 2 Solution: EF 3 2 n 2m 1.05 10 34 2/3 2 2 9.111031 3 2 6.4 1028 2/3 6.11039 1.53 1020 9.34 1019 J 9.34 1019 eV 5.84eV . 1.6 1019 IIT-JAM 2019 Q66. Which one of the following crystallographic planes represent 101 Miller indices of a cubic unit cell? z z z (a) (b) (c) x x (d) y y m z x y x Ans. : (b) Solution: Plane intercepts x: y:z a b c a b c : : : : a::c h k l 1 0 1 x a , y , z c Plane is parallel to y - axis and intersecting x and z - axis at a and c . Thus, option (b) is correct. H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 30 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q67. For using a transistor as an amplifier, choose the correct option regarding the resistances of base-emitter RBE and base-collector RBC junctions (a) Both RBE and RBC are very low (b) Very low RBE and very high RBC (c) Very high RBE and very low RBC (d) Both RBE and RBC are very high Ans. : (b) Q68. The output of following logic circuit can be simplified to X Y Z (a) X YZ (b) Y XZ (d) X Y Z (c) XYZ Ans. : (b) Solution: Output XY X Y Z Y Y Z XY XY XZ Y YZ XY XZ Y Y 1 X XZ Y XZ Q69. For a forward biased p-n junction diode, which one of the following energy-band diagrams is correct ( F is the Fermi energy) Conduction Band p -type n-type (a) Electron F p Energy Conduction Band p -type n-type (b) F n Valence Band Conduction Band p -type n-type (c) F p Valence Band Valence Band Conduction Band p -type n-type (d) F n Electron Energy F Electron Energy F p Electron Energy F n Valence Band Ans. : (a) H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 31 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q70. The location of Cs and Cl ions inside the unit cell of cacl crystal is shown in the figure. The Bravais lattice of CaCl is z Cl a y Cs a a x (a) Simple cubic (b) Body centred orthorhomble (c) Face centred cubic (d) Base centred orthorhombic Ans. : (a) Solution: Cesium-Chloride is made of two interpenetrating simple cubic lattices are displaced diagonally by half of the diagonal length. Thus, Bravais lattice of CsCl is simple cubic. The correct option is (a). Q71. In the X -ray diffraction pattern recorded for a simple cubic solid (lattice) parameter o o a 1 A ) using X -rays of wavelength 1 A , the first order diffraction peak(s) would appear for the (a) 100 planes (b) 112 planes (c) 210 planes (d) 220 planes Ans. : (a) Solution: In simple cubic cell, planes are present. The first order diffraction peak would appear for the first plane 10 0 . Q72. Sodium Na exhibits body-centred cubic (BCC) crystal structure with atomic radius 0.186 nm . The lattice parameter of Na unit cell is______ nm . Ans. : 0.43 Solution: For BCC, 3a 4r a 4r 3 4 0.186 3 a 0.43 nm H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 32 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics Q73. For the input voltage V1 200 mV sin 400 t , the amplitude of the output voltage V0 of the given OPAMP circuit is __________ V . (Round off to 2 decimal places) 35k 35k Rf 10k R1 35k Rf 10k R2 Rf 10k R3 Vi V0 Ans. : 11.03 35 Solution: v01 1 vi 4 5 200mV sin 400t 10 v02 v0 35 4 5 200mV sin 400t 10 35 35 4 5 200mV sin 400t 10 10 Vm 3.5 3.5 4.5 200 mV 11.03Volts Q74. The value of emitter current in the given circuit is _______ A . (Round off to 1 decimal places) VCC 10V 2M B 0.3V 2k 4k C 100 E C E Ans. : 444.9 Solution: I B VCC VBE RB 1 RE H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 33 fiziks Institute for NET/JRF, GATE, IIT‐JAM, M.Sc. Entrance, JEST, TIFR and GRE in Physics IB 10 0 3 9.7 A 3 2 10 101 2 10 2.202 106 6 I E 1 I B 101 The Zener current I z for the given circuit is ______ mA . VR IZ VZ = 20 V Vin = 40 V R 10k RL = 20 k Q75. 9.7 A 444.9 A 2.202 VL Ans. : 1 Solution: Open circuit voltage Vi 20k 2 40V 40 26.7 Volts 20k 10k 3 Vi VZ , Zener “ON” IL VZ 20 40 20 1mA and I R 2mA 10 RL 20 I Z I R I L 1mA Q76. The decimal equivalent of the binary number 110.101 is _______. Ans. : 6.625 Solution: 110 101 12 1 21 0 20 1 21 0 22 1 23 1 1 4 2 0 0 8 2 6 0.5 0 0.125 6.625 H.No. 40-D, Ground Floor, Jia Sarai, Near IIT, Hauz Khas, New Delhi-110016 Phone: 011-26865455/+91-9871145498 Website: www.physicsbyfiziks.com | Email: fiziks.physics@gmail.com 34