68) Match List I with List II : List I Coefficients of s 2 + a 1 s + a 0 = 0 (A) a 1 2 > 4a 0 (B) a 1 2 = 4a 0 (C) a 1 2 < 4a 0 (D) a 1 = 0 a 0 ≠ 0 List II Nature of Roots (I) Negative real and equal (II) Conjugate Imaginary (III) Negative Real and Unequal (IV) Conjugate Complex (Real part negative) Choose the correct answer from the options given below : (1) (A)-(IV), (B)-(II), (C)-(I), (D)-(III) (2) (A)-(III), (B)-(IV), (C)-(I), (D)-(II) (3) (A)-(III), (B)-(I), (C)-(IV), (D)-(II) (4) (A)-(IV), (B)-(III), (C)-(II), (D)-(I) ...

66) Match List I with List II : List I (A) JFET (B) MOSFET (C) Tunnel diode (D) HEMT List II (I) Two-dimensional electron gas (II) Negative resistance device (III) Enhancement mode (IV) Voltage controlled resistor Choose the correct answer from the options given below : (1) (A)-(IV), (B)-(III), (C)-(II), (D)-(I) (2) (A)-(III), (B)-(II), (C)-(I), (D)-(IV) (3) (A)-(II), (B)-(I), (C)-(IV), (D)-(III) (4) (A)-(I), (B)-(IV), (C)-(III), (D)-(II) Answer: A Previous yr Question papers with Full Explanations → El...

65) For transducers, following statements are given : (A) An optical interferometer is useful for measuring extremely small motions (B) The damping ratio of a seismic instrument should be low for good dynamic performance (C) A rate gyro is a relative motion measuring device (D) A pneumatic motion transducer is non linear over a wide range of motion (E) A piezoelectric accelerometer can only be used for static motion measurement Choose the correct answer from the options given below : (1) (A) and (B) only (2) (A) and (C) only (3) (A) and (D) only (4) (C) and (E) only Answer: C Solution (A) An optical interferometer is useful for measuring extremely small displacements. (B) A seismic instrument is used to measure vibration. For good dynamic performance, its damping ratio should be in the range of 0.7 to 1...

64) Which of the following statements are correct about AC Bridges? (A) The Maxwell bridge is suitable for measurement of Medium-Q Coils (1 < Q < 10) (B) For measurements at low frequencies, an oscillator supplies excitation voltage while at higher frequencies, power line may serve as source of excitation (C) The Hay bridge is convenient for measuring very low-Q coils (Q < 1) (D) The Schering bridge is particularly useful for the measure of insulating properties i.e. for phase angles nearly 90° Choose the correct answer from the options given below : (1) (A) and (B) only (2) (A) and (D) only (3) (B) and (C) only (4) (B) and (D) only Answer: B Previous yr Question papers with Full Explanations → Electronics and Communiaction Study Materials →

63) Which of the following statements are correct about an IR photodiode? (A) IR photodiodes cause no risk of contamination or physical damage to the object surface (B) For higher temperatures, IR photodiode devices have shorter life (C) IR photodiodes can not be used to measure temperature of moving objects (conveyor belt) (D) IR photodiodes are capable of measuring hazardous and physically in accessible process Choose the correct answer from the options given below : (1) (A), (B) and (C) only (2) (B) and (C) only (3) (A) and (D) only (4) (B), (C) and (D) only Answer: C Previous yr Question papers with Full Explanations → Electronics and Communiaction Study Materials →

61) In digital data transmission, a line code should have the following properties: (A) Transmission bandwidth should be as small as possible (B) Transmitted power should be as high as possible (C) Transmission bandwidth should be as high as possible (D) Transmitted power should be as low as possible Choose the correct answer from the options given below : (1) (A) and (B) only (2) (B) and (C) only (3) (C) and (D) only (4) (A) and (D) only Answer: D Previous yr Question papers with Full Explanations → Electronics and Communiaction Study Materials →

  60) Read the following statements : (A) A selective filtering method is most commonly used for the generation of SSB signals (B) A selective filtering method is most commonly used for the generation of DSB signals (C) A VSB modulator is also known as asymmetric side band system (D) A VSB modulator is also known as symmetric side band system Choose the correct answer from the options given below : (1) (A) and (B) only (2) (A) and (C) only (3) (B) and (D) only (4) (B) and (C) only Answer: B Previous yr Question papers with Full Explanations → Electronics and Communiaction Study Materials →

  Induction Motor Dynamics: Slip and Regenerative Braking Explained Understanding Induction Motors: Regenerative Braking, Slip, and Speed Induction motors are the heart of industrial machinery. To understand how they work—and how they stop—you need to grasp three core concepts: Synchronous Speed , Rotor Speed , and Slip . 1. What is Synchronous Speed (N s )? Synchronous speed is the speed of the rotating magnetic field produced by the stator. It is entirely dependent on the electrical supply frequency and the physical construction of the motor. N s = (120 × f) / P f: Supply Frequency (e.g., 50Hz or 60Hz) P: Number of Poles in the motor The 2πN Confusion You may have seen 2πN / 60 . This is not the formula for synchronous speed itself, but a conversion factor. It converts speed from RPM (li...