Tiêu đề 26. SEMI CONDUCTORS and ELECTRONIC DEVICES Hard.pdf ✅

1. A 2V battery is connected across the points A and B as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to A is (a) 0.2 A (b) 0.4 A (c) Zero (d) 0.1 A 2. Current in the circuit will be (a) A 40 5 (b) A 50 5 (c) A 10 5 (d) A 20 5 3. Find the magnitude of current in the following circuit (a) 0 (b) 1 amp (c) 0.1 amp (d) 0.2 amp 4. The diode used in the circuit shown in the figure has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milliwatts. What should be the value of the resistor R, connected in series with the diode for obtaining maximum current (a) 1.5  (b) 5  (c) 6.67  (d) 200  5. For a transistor amplifier in common emitter configuration for load impedance of 1 k (hfe = 50 and hoe = 25) the current gain is (a) – 5.2 (b) – 15.7 (c) – 24.8 (d) – 48.78 6. In the following common emitter configuration an NPN transistor with current gain  = 100 is used. The output voltage of the amplifier will be (a) 10 Mv (b) 0.1 V (c) 1.0 V (d) 10 V 7. While a collector to emitter voltage is constant in a transistor, the collector current changes by 8.2 mA when the emitter current changes by 8.3 mA. The value of forward current ratio hfe is (a) 82 (b) 83 (c) 8.2 (d) 8.3 8. The transfer ratio of a transistor is 50. The input resistance of the transistor when used in the common-emitter configuration is 1 K. The peak value for an ac input voltage of 0.01 V peak is (a) 100 A (b) 0.01 Ma (c) 0.25 mA (d) 500  A 9. In a common base amplifier circuit, calculate the change in base current if that in the emitter current is 2 mA and  = 0.98 (a) 0.04 mA (b) 1.96 Ma (c) 0.98 Ma (d) 2 Ma 10. A cell of 2V, 1 is balanced at 1.9 m. Then what is balanced length for ideal cell of 2V ? (a) 1.9 m (b) > 1.9 m (c) < 1.9 m (d) None of these 11. A voltmeter of variable ranges 3V, 15C, 150V is to be designed by connecting resistances R1, R2, R3 in series with a galvanometer of resistance G = 20, as shown in Fig. The galvanometer gives full pass through its coil. Then, the resistances R1, R2 and R3 (in kilo ohms) should be, respectively - G R1 R2 R3 Vcommon 3V 15V 150V (a) 3, 12, 135 (b) 2.98, 12, 135 (c) 2.98, 14.98, 149.98 (d) None of these 12. Two cells of emf E1 and E2 (E2> E1) are connected in series in a secondary circuit of a potentiometer experiment for determination of emf. The balancing length is found to be 825 cm. Now when the terminals of cell of emf E1 are reversed, then the balancing length is found to be 225 cm. The ratio of E1 and E2 is, then- (a) 2 : 3 (b) 4 : 7 (c) 7 : 4 (d) None of these 13. In an experiment on measurements of emf of a cell by a potentiometer, the balancing length for a cell of emf E and internal resistance r is found to be . Now if another cell of emf E and internal resistance 2r is connected in parallel to the first cell and balancing length determined, then the balancing length will be- (a)  (b) 2  (c) 2  (d)  3 2 14. In the figure battery E is balanced on 55 cm length of potentiometer wire but when a resistance of 10 is connected in parallel with the battery then it balances on 50 cm length of the potentiometer wire. The internal resistance r of the battery is- 1mV 1K 10K Vout 1.5 V R 0.5 V – 4 V 3 – 1 V 20 20 5V 30 i A B 10  10 
G E r 2V 1m A B (a) 1  (b) 3  (c) 10  (d) 5  15. The metre bridge circuit shown in figure is balanced when jockey J divides wire AB into two parts AJ and BJ in the ratio 1 : 2. The unknown resistance Q is - G 2 E Q A J B (a) 1  (b) 2  (c) 4  (d) 3  16. In a potentiometer experiment a cell of e.m.f 1.5 V connected in the secondary circuit gives a balancing length of 165 cm of the wire. If a resistance of 5  is connected in parallel to the cell, the balancing length of the wire is 150 cm. The internal resistance of the cell is - (a) 5  (b) 1.5  (c) 1  (d) 0.5  17. A 6 volt battery is connected to the terminals of a three metre long wire of uniform thickness and resistance of 100 ohm. The difference of potential between two points on the wire separated by a distance of 50 cm will be - (a) 2 volt (b) 3 volt (c) 1 volt (d) 1.5 volt 18. In a meter bridge experiment, the ratio of the left gap resistance to right gap resistance is 2 : 3, the balance point from left is - (a) 60 cm (b) 50 cm (c) 40 cm (d) 20 cm 19. A battery of 6 volt is connected to terminals of 3m long wire of uniform thickness. The potential difference between two points separated by 50 cm on the wire will be - (a) 1 volt (b) 1.5 volt (c) 2 volt (d) 3 volt 20. A meter bridge with resistance R1 and R2 connected in two gaps is balanced at 0.4 m from zero end. If smaller resistance is connected in series with 10  resistance, the balance point is shifted to 0.4 m from other end. The value of smaller resistance is - (a) 40  (b) 60  (c) 20  (d) 8  21. If galvanometer has 500  resistance and R = 5000 , then what should be the resistance connected to galvanometer in parallel to it so that its deflection reduces to half – () S R K1 10 V G () K2 (a) 544  (b) 500  (c) 455 (d) None 22. The length of a wire of a potentiometer is 100 cm and the emf of its standard cell is E volt. It is employed to measured emf of a battery whose internal resistance is 0.5 . If the balance point is obtained at  = 30 cm from the positive end, the emf of the battery is - (a) 0.2 E (b) 0.3 E (c) 0.4 E (d) 0.5 E 23. In a potentiometer experiment, the balancing point will a cell is at 560 cm. When an external resistance of 10  is connected in parallel to the cell, the balancing length changes to 412 cm. The internal resistance of the cell in ohms is : (a) 3.6 (b) 2.4 (c) 1.2 (d) 0.6 24. If resistance of galvanometer is 100  and deflection occurs in it when connected in circuit is of 20 divisions. Then calculate figure of merit of galvanometer – G 2V 100 (a) 5 × 10–2 A/div (b) 2 × 10–4 A/div (c) 2 × 10–2 A/div (d) 5 × 10–4 A/div 25. Shown in the figure below is a meter-bridge set up with null deflection in the galvanometer. G 20cm 55 R The value of the unknown resistor R is - (a) 13.75  (b) 220  (c) 110  (d) 55  26. A standard cell of 1.08 V is balanced by the p.d. across 90 cms of a meter long wire supplied by a cell of emf 2V through a series resistor of resistance 2 . If the internal resistance of cell in primary circuit is zero then the resistance per unit length of potentiometer wire is : (a) 3 ohm/cm (b) 0.3 ohm/cm (c) 3 ohm/m (d) 3 ohm/mm 27. A cell of emf e and internal resistance r is put across a variable resistor of zero to 'R'. The VI curve indicates that -
Potential difference (V) O Current (I) (a) Internal resistance is zero (b) Internal resistance is I V (c) Internal resistance is I e – V (d) None 28. In the given circuit, P  R, the reading of the galvanometer is same with switch S open or closed. Then - R P Q G S V (a) IR = IG (b) IP = IG (c) IQ = IG (d) IQ = IR 29. A 10 m long wire of resistance 20  is connected in series with a battery of emf 3V (negligible internal resistance) and a resistance of 10 . Find the potential gradiant along the wire - (a) 3 V/m (b) 0.2 V/m (c) 0.1 V/m (d) 0.3 V/m 30. In the given circuit total resistance of wire is 3, then the value of E is - /2 E G = 100 cm 4V R = 2 1  A B (a) 0.75 V (b) 1 V (c) 2V (d) None 31. A zener diode is to be used as a voltage regulator. Identify the correct set up – (a) Rs + – RL (b) Rs + – RL (c) Rs + – RL (d) Rs + – RL 32. If a semiconductor has an intrinsic carrier concentration of 1.41 × 1016 m–3 , when doped with 1021 m–3 phosphorus, then the concentration of holes at room temperature will be – (a) 2 × 1021 (b) 2 × 1011 (c) 1.41 × 1010 (d) 1.41 × 1016 33. If lattice parameter for a crystalline structure is 3.6 Å, then atomic radius in fcc crystal in Å is – (a) 7.20 Å (b) 1.80 Å (c) 1.27 Å (d) 2.90 Å 34. In a p–type semiconductor the acceptor level is situated 57 meV above the valence band. The maximum wavelength of light required to produce a hole will be – (a) 57 Å (b) 57 × 10–3 Å (c) 217100 Å (d) 11.61 × 10–33 m 35. An p-n junction (d) shown in the figure can act as a rectifier. An alternating current source (V) is connected in the circuit. The current (I) in the resistor R can be shown by (a) (b) (c) (d) 36. An n – p – n transistor circuit has  = 0.985. If Ic = 2mA, then value of Ib is - (a) 0.03 mA (b) 0.003 mA (c) 0.66 mA (d) 0.015 mA 37. The circuit shown in following figure contains two diode D1 and D2 each with a forward resistance of 50 ohms and with infinite backward resistance. If the battery voltage is 6V, the current through the 100 ohm resistance (in amperes) is -
D1 150 50 100 D2 6V (a) Zero (b) 0.02 (c) 0.03 (d) 0.036 38. A sinusoidal voltage of peak value 200 volt is connected to a diode and resistor R in the circuit shown so that half wave rectification occurs. If the forward resistance of the diode is negligible compared to R the rms voltage (in volt) across R is approximately - R E0 = 200 Volt (a) 200 (b) 100 (c) 2 200 (d) 280 39. Find VAB 10 10 10 VAB 30V (a) 10 V (b) 20 V (c) 30V (d) None of these 40. Type of bonds present in the semiconductors is - (a) Covalent bond (b) Monovalent bond (c) Co-ordinate bond (d) None of these 41. A zener diode is to be used as a voltage regulator. Identify the correct set up – RS RL + – RS RL + – I II RS RL + – RS RL + – (a) I (b) II (c) III (d) IV 42. A diode is connected to 220 V (rms) ac in series with a capacitor as shown in figure. The voltage across the capacitor is – 220V ac C (a) 220 V (b) 110 V (c) 311.1 V (d) 2 220 V 43. For a tansistor working as common base amplifier, the emitter current is 7.2 mA. The current gain is 0.96. The collector current is - (a) 0.96 × 7.2 mA (b) 0.72 0.96 mA (c) 0.96 – 7.2 mA (d) 7.2 A – 2 × 0.96 mA 44. A combination of logic gates has the truth table below. P Q Z 0 0 0 0 1 1 1 0 1 1 1 1 Which of the following combinations has this truth table? (a) NOT NOR Z P Q (b) NOT NAND Z P Q (c) NAND NOR Z P Q NOT (d) NAND Z P Q NOT 45. In the circuit shown, the current through the ideal diode is – 80 2V 20 (a) 75 mA (b) 20 mA (c) 100 mA (d) 25 mA 46. The following figure shows a logic gate circuit with two inputs A and B and output C. The voltage waveforms of A, B and C are as shown in second figure below :