Download PrepIQ 17CompA1 Electronics A Ultimate Exam and more Exams Technology in PDF only on Docsity!
Question 1. Which SI unit is used to measure electric charge? A) Ampere B) Coulomb C) Volt D) Ohm Answer: B Explanation: The coulomb (C) is the SI unit for electric charge; one coulomb equals the charge transferred by a current of one ampere in one second. Question 2. Ohm’s law states that V = I × R. If a resistor has a resistance of 10 Ω and a current of 2 A flows through it, what is the voltage across the resistor? A) 5 V B) 10 V C) 20 V D) 0.5 V Answer: C Explanation: V = I × R = 2 A × 10 Ω = 20 V. Question 3. In a series circuit containing three resistors of 4 Ω, 6 Ω, and 10 Ω, the total resistance is: A) 20 Ω B) 10 Ω C) 4 Ω D) 6 Ω Answer: A Explanation: Resistances add in series: 4 Ω + 6 Ω + 10 Ω = 20 Ω.
Question 4. Two 5 Ω resistors are connected in parallel. What is the equivalent resistance? A) 10 Ω B) 2.5 Ω C) 5 Ω D) 1 Ω Answer: B Explanation: 1/Req = 1/5 + 1/5 = 2/5 → Req = 5/2 = 2.5 Ω. Question 5. The power rating of a resistor is 0.5 W. If the resistor dissipates 0.4 W, it is: A) Overloaded B) Within rating C) Underrated D) Burning Answer: B Explanation: The dissipated power (0.4 W) is below the maximum rating (0.5 W), so the resistor operates safely. Question 6. A resistor color code reads red-violet-yellow-gold. What is its nominal resistance and tolerance? A) 27 kΩ ± 5 % B) 2.7 kΩ ± 5 % C) 270 Ω ± 10 % D) 27 Ω ± 2 % Answer: A
Explanation: At the moment of connection, the inductor’s current cannot change instantly, so it acts like a short circuit (zero voltage across it). Question 10. When AC passes through a capacitor, the current leads the voltage by: A) 0° B) 45° C) 90° D) 180° Answer: C Explanation: In a pure capacitive reactance, current leads voltage by 90 degrees. Question 11. A step-down transformer has a primary of 120 V and a secondary of 12 V. What is the turns ratio (N₁:N₂)? A) 10: B) 1: C) 12: D) 120: Answer: A Explanation: Voltage ratio equals turns ratio; 120 V : 12 V = 10 : 1. Question 12. Mutual inductance between two coils is 5 mH. If the primary current changes at 2 A/s, the induced emf in the secondary is: A) 0.01 V B) 0.1 V C) 10 V D) 0.5 V
Answer: B Explanation: Induced emf = M · di/dt = 5 mH × 2 A/s = 0.01 H × 2 = 0.01 V? Wait 5 mH = 0.005 H, so 0.005 × 2 = 0.01 V. Correct answer is A (0.01 V). Question 13. Which of the following best describes the band gap of a semiconductor? A) Zero eV B) Very large, > 5 eV C) Small, typically 0.5–2 eV D) Same as a metal Answer: C Explanation: Semiconductors have a moderate band gap (≈0.5–2 eV) allowing controlled conductivity. Question 14. Doping silicon with phosphorus creates: A) P-type material B) N-type material C) Intrinsic silicon D) Insulating silicon Answer: B Explanation: Phosphorus adds extra electrons, producing N-type (negative) semiconductor. Question 15. In an N-type semiconductor, the majority carriers are: A) Holes B) Electrons C) Ions D) Photons
Answer: B Explanation: Zener diodes exploit controlled avalanche breakdown at a specified reverse voltage for voltage regulation. Question 19. The primary use of a Light-Dependent Resistor (LDR) is: A) To amplify signals B) To switch high currents C) To vary resistance with light intensity D) To store charge Answer: C Explanation: LDRs change resistance based on incident light, useful in light-sensing circuits. Question 20. An LED emits light when: A) Reverse-biased B) Forward-biased above its knee voltage C) Operated at zero voltage D) Connected in series with a capacitor Answer: B Explanation: LEDs conduct and emit photons when forward-biased above their forward voltage (≈ 2 V for red). Question 21. A photodiode operated in photovoltaic mode generates: A) Current only when reverse-biased B) Voltage without external bias when illuminated C) No current under any condition D) Continuous AC output
Answer: B Explanation: In photovoltaic mode, a photodiode produces a voltage (and current) when illuminated, without external bias. Question 22. Which of the following statements about a BJT is correct? A) Current flows from collector to emitter in an NPN when base is high. B) Voltage controls the current in a BJT. C) It is a voltage-controlled device. D) It has three terminals: gate, source, drain. Answer: A Explanation: In an NPN BJT, with sufficient base current, collector-to-emitter current flows from collector to emitter. Question 23. The DC current gain β of a BJT is defined as: A) Ic / Ib B) Ie / Ic C) Vc / Vb D) Ib / Ic Answer: A Explanation: β (beta) = collector current (Ic) divided by base current (Ib). Question 24. In a common-emitter BJT configuration, the voltage gain is: A) Approximately unity B) Greater than one (phase inversion) C) Zero D) Infinite
D) Any voltage Answer: C Explanation: Enhancement-mode MOSFETs are normally off; a positive Vgs above the threshold creates a conductive channel. Question 28. Which MOSFET configuration is best for a high-impedance input stage? A) Depletion-mode JFET B) Enhancement-mode n-channel MOSFET C) PNP BJT D) Zener diode Answer: B Explanation: Enhancement-mode MOSFETs have extremely high input impedance due to insulated gate. Question 29. In a common-source MOSFET amplifier, the output is: A) In-phase with the input B) 180° out of phase with the input C) Identical voltage as the input D) Zero Answer: B Explanation: Common-source configuration provides voltage gain with a 180° phase inversion. Question 30. The primary function of a rectifier circuit is to: A) Amplify AC signals B) Convert AC to DC
C) Store energy D) Generate high frequency Answer: B Explanation: Rectifiers convert alternating current (AC) into direct current (DC). Question 31. In a bridge rectifier, how many diodes conduct during each half-cycle? A) One B) Two C) Three D) Four Answer: B Explanation: Two diodes conduct simultaneously, directing current in the same polarity during each half-cycle. Question 32. A half-wave rectifier has a peak output voltage of 12 V. What is its average (DC) output voltage? A) 12 V B) 6 V C) 3.8 V D) 0 V Answer: C Explanation: Vavg = Vp/π for half-wave; 12 V/π ≈ 3.82 V. Question 33. An RC integrator circuit produces an output that is: A) The derivative of the input B) The integral (area) of the input
A) –Rf/Rin B) +Rf/Rin C) –Rin/Rf D) +Rin/Rf Answer: A Explanation: The gain of an inverting amplifier is –(feedback resistor ÷ input resistor). Question 37. A voltage follower (buffer) using an op-amp provides: A) Signal inversion with gain of – B) Unity gain with high input impedance C) Amplification of 10× D) Frequency multiplication Answer: B Explanation: The voltage follower has a gain of 1, high input impedance, and low output impedance, ideal for buffering. Question 38. Which op-amp configuration is used as a summing amplifier? A) Non-inverting with feedback B) Inverting with multiple input resistors C) Voltage follower D) Comparator Answer: B Explanation: An inverting amplifier with several input resistors connected to different sources sums the currents, producing a weighted sum. Question 39. A comparator differs from a linear op-amp circuit because it:
A) Provides a continuous analog output B) Switches its output between two saturation levels based on input comparison C) Requires feedback for stability D) Operates only at DC Answer: B Explanation: Comparators output a high or low level (saturation) depending on which input is greater; they are open-loop devices. Question 40. The binary representation of the decimal number 45 is: A) 101101 B) 110010 C) 100101 D) 111001 Answer: A Explanation: 45₁₀ = 32 + 8 + 4 + 1 = 101101₂. Question 41. Convert the binary number 1101101 to decimal. A) 109 B) 101 C) 109 D) 115 Answer: A Explanation: 1×2⁶ +1×2⁵ +0×2⁴ +1×2³ +1×2² +0×2¹ +1×2⁰ = 64+32+0+8+4+0+1 = 109. Question 42. The hexadecimal equivalent of the binary number 1010 1100 is:
Question 44. Adding two 4-bit binary numbers 0111 (7) and 0101 (5) yields a 5 - bit result of: A) 01100 B) 10100 C) 11000 D) 11100 Answer: A Explanation: 7 + 5 = 12 → 1100₂; expressed in 5 bits it is 01100. Question 45. The Boolean expression for a NAND gate with inputs A and B is: A) A · B B) A + B C) (A · B)′ D) (A + B)′ Answer: C Explanation: NAND = NOT (A AND B) = (A·B)′. Question 46. Which logic gate produces a high output only when an odd number of its inputs are high? A) AND B) OR C) XOR D) NAND Answer: C Explanation: XOR (exclusive-OR) outputs high when an odd number of inputs are high.
Question 47. The truth table for a NOR gate shows a high output when: A) All inputs are high B) Any input is high C) All inputs are low D) Exactly one input is high Answer: C Explanation: NOR = NOT (A + B); output is high only when all inputs are 0. Question 48. A 2-input multiplexer (MUX) selects between two data inputs D and D1 based on select line S. The output Y is given by: A) Y = D0·S + D1·S′ B) Y = D0·S′ + D1·S C) Y = D0 + D D) Y = D0 · D Answer: B Explanation: When S=0, Y = D0; when S=1, Y = D1, so Y = D0·S′ + D1·S. Question 49. Which of the following is a universal gate? A) AND B) OR C) NAND D) XOR Answer: C Explanation: NAND (and NOR) can be combined to implement any Boolean function.
A) Remain the same B) Reset to 0 C) Set to 1 D) Toggle Answer: D Explanation: JK = 1,1 causes the output to toggle on each clock edge. Question 54. The characteristic equation of a D-type flip-flop is: A) Qₙ₊₁ = D B) Qₙ₊₁ = J·Qₙ′ + K·Qₙ C) Qₙ₊₁ = T·Qₙ′ D) Qₙ₊₁ = Qₙ Answer: A Explanation: The D-FF transfers the D input to Q on the active clock edge. Question 55. A synchronous 4-bit binary up-counter will count from 0 to: A) 7 B) 8 C) 15 D) 16 Answer: C Explanation: 4 bits can represent 0–15 (2⁴ – 1). Question 56. In a shift register, data is moved: A) Parallel only
B) Serial only C) Either serially or parallel depending on configuration D) Not moved at all Answer: C Explanation: Shift registers can be configured for serial-in/serial-out, serial-in/parallel-out, etc. Question 57. The main advantage of Very-Large-Scale Integration (VLSI) over Small-Scale Integration (SSI) is: A) Higher power consumption B) Larger physical size C) Greater component density and functionality on a single chip D) Simpler design process Answer: C Explanation: VLSI packs millions of transistors on one chip, enabling complex functions in tiny packages. Question 58. Which memory type is non-volatile and can be electrically erased and re-programmed? A) SRAM B) DRAM C) EEPROM D) Cache Answer: C Explanation: EEPROM retains data without power and can be erased/programmed electrically.
