AP ECET ELECTRONICS AND COMMUNICATION ENGINEERING (ECE) Multiple Choice Questions (MCQs)

46. What is the working principle of a Thyristor (SCR)?

• A) It operates by using a bipolar junction transistor.
• B) It acts as a switch and is triggered by a pulse.
• C) It only allows current to flow in one direction.
• D) It is used for DC power regulation.

Answer: B

47. Which of the following is a key feature of a TRIAC?

• A) It can only be triggered in one direction.
• B) It can conduct current in both directions.
• C) It is primarily used in AC circuits.
• D) Both B and C.

Answer: D

48. What is the main advantage of using IGBT (Insulated Gate Bipolar Transistor)?

• A) High speed operation
• B) High voltage and current handling capability
• C) Low cost
• D) Low power loss

Answer: B

49. In which of the following applications are Power BJTs commonly used?

• A) Amplifiers
• B) Rectifiers
• C) Power regulation
• D) Oscillators

Answer: C

50. Which inverter topology is commonly used in PWM inverters for controlling motor speed?

• A) Single-phase
• B) Three-phase
• C) Multilevel inverter
• D) DC-AC inverter

Answer: B

51. What is the primary function of a Single-Phase Inverter?

• A) Convert DC to AC
• B) Convert AC to DC
• C) Voltage regulation
• D) Current conversion

Answer: A

52. Which of the following is the key difference between Off-line and On-line UPS systems?

• A) Off-line UPS does not provide backup power.
• B) On-line UPS always provides backup power without any switching delay.
• C) On-line UPS is used only for critical systems.
• D) There is no difference between Off-line and On-line UPS.

Answer: B

53. What is the main purpose of using an Opto-electronic device such as an LDR (Light Dependent Resistor)?

• A) To measure temperature
• B) To detect light intensity
• C) To amplify signals
• D) To generate electricity

Answer: B

54. Which opto-electronic device is primarily used for converting light into an electrical signal?

• A) Photodiode
• B) Phototransistor
• C) Photovoltaic cell
• D) LDR

Answer: A

55. What is the primary application of a Thermocouple?

• A) Temperature measurement
• B) Light detection
• C) Signal amplification
• D) Pressure sensing

Answer: A

56. What is the working principle of an LVDT (Linear Variable Differential Transformer)?

• A) It measures angular displacement.
• B) It measures linear displacement.
• C) It measures temperature.
• D) It converts light into electrical signals.

Answer: B

57. Which of the following is NOT an industrial heating method?

• A) Induction heating
• B) Resistance heating
• C) Ultrasonic heating
• D) Laser heating

Answer: C

58. Which of the following statements is true about the Transfer Function in control systems?

• A) It represents the input-output relationship in the Laplace domain.
• B) It is used to describe the frequency response.
• C) It can be derived from the state-space model.
• D) All of the above.

Answer: D

59. What is the definition of an Open-loop system in control systems?

• A) A system that continuously adjusts its output based on input.
• B) A system where the output is not fed back to the input.
• C) A system with feedback control.
• D) A system that only operates in closed-loop conditions.

Answer: B

60. Which of the following is a characteristic of a second-order system in control theory?

• A) It has a transfer function with two poles.
• B) It exhibits oscillatory behavior depending on damping.
• C) It is used for high-precision applications.
• D) All of the above.

Answer: D