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Question 1. Which of the following statements best describes the purpose of an ESD wrist strap when working on sensitive electronic components? A) It grounds the user to prevent electric shock. B) It prevents static charge buildup on the user’s body. C) It isolates the user from the power supply. D) It measures the voltage of the circuit. Answer: B Explanation: An ESD wrist strap provides a low-impedance path to ground, dissipating static electricity that could damage components. Question 2. A resistor has the color bands brown-black-red-gold. What is its resistance value and tolerance? A) 1 kΩ ± 5 % B) 10 kΩ ± 5 % C) 1 kΩ ± 10 % D) 10 kΩ ± 10 % Answer: A Explanation: Brown (1), black (0), red (×100) gives 1 × 10² Ω = 1 kΩ; gold indicates ±5 % tolerance. Question 3. Using Ohm’s Law, what current flows through a 220 Ω resistor when 12 V is applied across it? A) 0.054 A B) 0.055 A C) 0.056 A D) 0.057 A Answer: B Explanation: I = V/R = 12 V / 220 Ω = 0.0545 A ≈ 0.055 A. Question 4. Which unit conversion correctly changes 0.003 μF to nanofarads (nF)?
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A) 3 nF B) 30 nF C) 0.3 nF D) 0.03 nF Answer: A Explanation: 1 μF = 1000 nF, so 0.003 μF = 3 nF. Question 5. In a DC series circuit with three resistors of 10 Ω, 20 Ω, and 30 Ω connected to a 12 V source, what is the total current? A) 0.2 A B) 0.3 A C) 0.4 A D) 0.5 A Answer: A Explanation: Total R = 60 Ω; I = V/R = 12 V / 60 Ω = 0.2 A. Question 6. For a parallel network of two resistors, 100 Ω and 200 Ω, connected to a 9 V source, what is the voltage across each resistor? A) 3 V B) 6 V C) 9 V D) 12 V Answer: C Explanation: In parallel, voltage is the same across all branches, equal to the source voltage (9 V). Question 7. Which of the following particles has a negative charge? A) Proton B) Neutron C) Electron
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Question 11. An inductor of 2 mH is connected to a 500 Hz AC source. What is its inductive reactance (X_L)? A) 6.28 Ω B) 12.57 Ω C) 31.4 Ω D) 62.8 Ω Answer: C Explanation: X_L = 2πfL = 2π·500·0.002 H ≈ 6.28 Ω? Wait compute: 2π·500 = 3141.6; ×0.002 = 6.283 Ω. Actually answer should be A (6.28 Ω). Correction: Answer: A. Explanation: Using X_L = 2πfL gives 6.28 Ω. Question 12. Which diode is specifically designed to maintain a constant voltage across a load when reverse-biased? A) Schottky diode B) Zener diode C) LED D) Photodiode Answer: B Explanation: Zener diodes exploit breakdown to clamp voltage in reverse bias. Question 13. In a BJT NPN transistor, which terminal must be at a higher potential than the emitter for normal active mode operation? A) Collector B) Base C) Both collector and base D) Neither; emitter is highest Answer: C Explanation: For active mode, V_BE > 0 (base higher than emitter) and V_CB > 0 (collector higher than base).
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Question 14. A MOSFET is turned on when the voltage at its gate exceeds a certain threshold. Which MOSFET type operates with a positive gate-source voltage to conduct? A) N-channel enhancement B) P-channel enhancement C) N-channel depletion D) P-channel depletion Answer: A Explanation: N-channel enhancement MOSFETs require V_GS > V_TH to create a conductive channel. Question 15. Which integrated circuit is commonly used as a 555 timer in astable mode to generate a square wave? A) 741 B) 7805 C) LM D) 4017 Answer: C Explanation: The LM555 is the classic timer IC for generating oscillating waveforms. Question 16. An op-amp configured as a non-inverting amplifier has a gain of 5. Which resistor ratio produces this gain? A) R_f / R_in = 4 B) (R_f + R_in) / R_in = 5 C) R_in / R_f = 5 D) R_f = 5·R_in Answer: B Explanation: Non-inverting gain = 1 + (R_f / R_in); setting 1 + (R_f / R_in) = 5 gives R_f / R_in = 4. Question 17. The RMS value of a sine wave with a peak amplitude of 20 V is:
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Answer: C Explanation: Parallel resonance presents a high impedance because inductive and capacitive currents cancel. Question 21. Convert the binary number 101101₂ to hexadecimal. A) 2D B) 2B C) 3A D) 3D Answer: A Explanation: Grouping bits: 1011 = B, 0101 = 5 → actually 101101 = 2D? Let's compute: 101101₂ = 0b101101 = 45 decimal. 45 decimal = 0x2D. So answer A. Question 22. Which logic gate implements the Boolean function F = A·B + ¬A·C? A) NAND only B) NOR only C) Multiplexer D) XOR only Answer: C Explanation: The expression is a 2-to-1 multiplexer selecting B when A=1 and C when A=0. Question 23. The truth table for a NAND gate shows that the output is low only when: A) Both inputs are low B) Both inputs are high C) Either input is high D) Either input is low Answer: B Explanation: NAND outputs 0 only when all inputs are 1; otherwise output is 1.
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Question 24. In a D-type flip-flop, what is the output Q after a rising clock edge if D = 1? A) Q becomes 0 B) Q toggles C) Q becomes 1 D) Q remains unchanged Answer: C Explanation: The D input is transferred to Q on the active clock edge. Question 25. Which microcontroller architecture typically uses Harvard memory organization? A) 8051 B) PIC C) AVR D) ARM Cortex-M Answer: C Explanation: AVR microcontrollers separate program and data memory, characteristic of Harvard architecture. Question 26. A full-wave bridge rectifier receives a 120 V rms AC input. What is the approximate peak DC voltage after filtering (ignore diode drops)? A) 170 V B) 240 V C) 340 V D) 480 V Answer: A Explanation: V_peak = √2·V_rms = 1.414·120 V ≈ 170 V; bridge rectifier yields this peak after smoothing.
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A) To avoid damaging the meter’s fuse. B) Because voltage interferes with resistance reading. C) To prevent short-circuiting the power source. D) All of the above. Answer: D Explanation: Applying voltage can damage the meter, cause inaccurate readings, and create safety hazards. Question 31. On a DMM, which setting should be used to measure a 12 V DC battery? A) AC voltage range B) DC voltage range C) Resistance range D) Continuity beep Answer: B Explanation: DC voltage mode measures the direct-current potential of a battery. Question 32. An oscilloscope’s trigger level is set too high relative to the signal amplitude. What is the likely result? A) Stable single-sweep display B) No waveform displayed C) Continuous rolling trace D) Inverted waveform Answer: B Explanation: If the trigger never reaches the set level, the scope cannot synchronize and shows no stable trace. Question 33. A signal generator outputs a 1 kHz sine wave at 5 V peak-to-peak. What is its RMS voltage? A) 1.77 V B) 2.5 V
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C) 3.54 V
D) 5 V
Answer: A Explanation: V_pp = 5 V → V_peak = 2.5 V → V_RMS = V_peak / √2 = 2.5 V / 1.414 ≈ 1.77 V. Question 34. Which troubleshooting method starts by checking power supply voltages before inspecting individual components? A) Divide and conquer B) Visual inspection C) Symptom-cause-effect analysis D) Functional testing Answer: C Explanation: Symptom-cause-effect analysis often begins with verifying that the system is powered correctly. Question 35. When soldering an SMT component, why is flux important? A) It raises the melting point of solder. B) It removes oxide layers, improving wetting. C) It cools the joint quickly. D) It acts as an insulator. Answer: B Explanation: Flux cleans metal surfaces, allowing solder to flow and bond properly. Question 36. Which connector type is commonly used for high-frequency video signals up to 4 GHz? A) BNC B) RJ- 45 C) USB-C D) HDMI
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Question 40. Which of the following is a characteristic of a Schottky diode compared to a regular PN diode? A) Higher forward voltage drop B) Slower reverse recovery time C) Lower forward voltage drop D) Higher reverse breakdown voltage Answer: C Explanation: Schottky diodes have a metal-semiconductor junction, resulting in a lower forward voltage (~0.3 V). Question 41. A 10 μF electrolytic capacitor is connected with polarity reversed. What is the most likely consequence? A) No effect; electrolytic caps are non-polar. B) Reduced capacitance but normal operation. C) Leakage current increase and possible explosion. D) Improved performance due to reverse bias. Answer: C Explanation: Reversing polarity stresses the dielectric, leading to leakage, heating, and possible venting. Question 42. In a series RLC circuit, if the inductive reactance is 50 Ω and the capacitive reactance is 30 Ω, what is the net reactance? A) 20 Ω inductive B) 20 Ω capacitive C) 80 Ω inductive D) 80 Ω capacitive Answer: A Explanation: Net X = X_L – X_C = 50 Ω – 30 Ω = 20 Ω inductive. Question 43. Which Boolean expression simplifies to A ⊕ B (exclusive OR)? A) A·B + ¬A·¬B
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B) A·¬B + ¬A·B
C) A + B
D) ¬A·¬B
Answer: B Explanation: XOR is true when inputs differ: A·¬B + ¬A·B. Question 44. A 555 timer configured in monostable mode is triggered once. What is the output waveform? A) Continuous square wave B) Single high-time pulse C) Sawtooth wave D) No output change Answer: B Explanation: Monostable mode produces a single output pulse of predetermined width per trigger. Question 45. Which type of memory is non-volatile and retains data when power is removed? A) RAM B) Cache C) ROM D) Register Answer: C Explanation: ROM (Read-Only Memory) stores data permanently without power. Question 46. In a digital system, the term “debounce” refers to: A) Reducing signal amplitude. B) Eliminating multiple transitions caused by mechanical switch bounce. C) Converting analog to digital signals. D) Synchronizing clocks.
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Question 50. In a three-phase Y-connected system, the line voltage is √3 times the phase voltage. If the phase voltage is 120 V, what is the line voltage? A) 120 V B) 208 V C) 240 V D) 360 V Answer: B Explanation: V_line = √3·V_phase = 1.732·120 V ≈ 208 V. Question 51. Which of the following describes the purpose of a heat sink attached to a power transistor? A) Increase the transistor’s gain. B) Provide mechanical support. C) Dissipate heat to maintain safe junction temperature. D) Reduce parasitic inductance. Answer: C Explanation: Heat sinks spread and radiate thermal energy away from the device. Question 52. A diode’s forward voltage drop at 20 mA is measured as 0.7 V. Which semiconductor material is most likely used? A) Germanium B) Silicon C) Gallium arsenide D) Schottky metal Answer: B Explanation: Silicon diodes typically have a forward drop around 0.6-0.7 V at moderate current. Question 53. When converting 0x3F to binary, what is the result?
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A) 00111111
B) 11110000
C) 11111100
D) 11001111
Answer: A Explanation: 0x3F = 3·16 + 15 = 48 + 15 = 63 decimal = 00111111₂. Question 54. In a digital counter, the term “ripple-carry” refers to: A) Simultaneous toggling of all bits. B) Sequential toggling causing propagation delay. C) A high-speed synchronous design. D) Counter overflow detection. Answer: B Explanation: Ripple-carry counters propagate the carry bit through each flip-flop sequentially, causing delay. Question 55. Which property of a material defines its ability to resist electric current? A) Conductivity B) Resistivity C) Permeability D) Capacitance Answer: B Explanation: Resistivity quantifies how strongly a material opposes current flow. Question 56. A 12 V DC motor draws 2 A at stall. What is the minimum power rating required for a protective fuse? A) 12 W B) 24 W C) 36 W
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Explanation: Bypass (decoupling) capacitors shunt high-frequency transients to ground, cleaning the supply. Question 60. The frequency of a crystal oscillator is primarily determined by: A) Supply voltage B) Temperature C) Physical dimensions of the quartz cut D) Load capacitance only Answer: C Explanation: The resonant frequency of a quartz crystal is set by its cut, size, and thickness. Question 61. Which of the following statements about a “voltage divider” is true? A) Output voltage is always greater than input voltage. B) Output voltage is proportional to the ratio of the two resistors. C) It cannot be used with AC signals. D) It requires an active component. Answer: B Explanation: V_out = V_in·(R2/(R1+R2)) shows proportionality to resistor ratio. Question 62. A resistor network is required to produce a 3.3 V reference from a 5 V supply. Which ratio of R_bottom to R_total gives the correct voltage? A) 0. B) 0. C) 0. D) 0. Answer: A Explanation: V_ref = V_in·(R_bottom / R_total); 3.3/5 = 0.66, actually ratio should be 0.66. Wait compute: 3.3/5 = 0.66, so answer B. Correction: Answer: B.
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Question 63. In a PWM (pulse-width modulation) signal with a frequency of 2 kHz and a duty cycle of 25 %, what is the average voltage if the peak is 10 V? A) 2.5 V B) 5 V C) 7.5 V D) 10 V Answer: A Explanation: Average = V_peak·Duty = 10 V·0.25 = 2.5 V. Question 64. Which of the following is a typical characteristic of a “Schmitt trigger” input? A) Linear amplification. B) Hysteresis between high and low thresholds. C) Unlimited gain. D) No input bias current. Answer: B Explanation: Schmitt triggers provide hysteresis, preventing noise-induced false switching. Question 65. A 0.5 μF capacitor and a 100 kΩ resistor form an RC low-pass filter. What is its – 3 dB cutoff frequency? A) 3.18 Hz B) 31.8 Hz C) 318 Hz D) 3.18 kHz Answer: B Explanation: f_c = 1/(2πRC) = 1/(2π·100 000·0.5 × 10⁻⁶) ≈ 3.18 Hz? Wait compute: RC = 0.05 s; 1/(2π·0.05) ≈ 3.18 Hz. Actually answer A (3.18 Hz). Correction: Answer A.
