Model Set - Electrical Engineering By NEC

Short Questions 60*1=60

1. Decibel relation for power gain is:

1. $N_{dB} = 20\log_{10}\left(\frac{V_2^2}{V_1^2}\right) + 20\log_{10}\left(\frac{Z_1}{Z_2}\right)$

2. $N_{dB} = 10\log_{10}\left(\frac{V_2^2}{V_1^2}\right) + 10\log_{10}\left(\frac{Z_1}{Z_2}\right)$

3. $N_{dB} = 20\log_{10}\left(\frac{V_2}{V_1}\right) + 10\log_{10}\left(\frac{Z_2}{Z_1}\right)$

4. $N_{dB} = 10\log_{10}\left(\frac{V_2}{V_1}\right) + 10\log_{10}\left(\frac{Z_2}{Z_1}\right)$

Show me the answer

Answer: 4) $N_{dB} = 10\log_{10}\left(\frac{V_2}{V_1}\right) + 10\log_{10}\left(\frac{Z_2}{Z_1}\right)$

Explanation: Power gain in decibels is derived from $P = \frac{V^2}{Z}$. Substituting into $N_{dB} = 10\log_{10}\left(\frac{P_2}{P_1}\right)$ gives: $N_{dB} = 10\log_{10}\left(\frac{V_2^2 / Z_2}{V_1^2 / Z_1}\right) = 10\log_{10}\left(\frac{V_2}{V_1}\right) + 10\log_{10}\left(\frac{Z_2}{Z_1}\right)$

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2. Maximum power that can be transferred from source to load is:

1. 25%

2. 75%

3. 50%

4. 100%

Show me the answer

Answer: 3) 50%

Explanation: According to the Maximum Power Transfer Theorem, maximum power is transferred when load resistance equals source resistance. At this condition, half of the total power is delivered to the load, and half is dissipated in the source resistance, so efficiency is 50%.

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3. Power factor $( \frac{R}{Z} )$ has maximum value of:

1. 0.0

2. 0.5

3. 1.0

4. 1.5

Show me the answer

Answer: 3) 1.0

Explanation: Power factor = $\frac{R}{Z}$, where $Z = \sqrt{R^2 + X^2}$. The maximum value occurs when $X = 0$ (purely resistive circuit), giving power factor = 1.

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4. At series resonance, the voltage across L or C is:

1. Equal to applied voltage

2. Less than applied voltage

3. Much more than applied voltage

4. Equal to voltage across R

Show me the answer

Answer: 3) Much more than applied voltage

Explanation: At series resonance, inductive and capacitive reactances cancel, but individual voltages across L and C can be Q times the supply voltage, where Q is the quality factor.

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5. The minimum phase transfer function is the one having .......

1. Poles and zeros in right hand side

2. Poles and zeros in left hand side

3. Poles in left hand side and zeros in right hand side

4. Poles in right hand side and zeros in left hand side

Show me the answer

Answer: 2) Poles and zeros in left hand side

Explanation: A minimum phase system has all poles and zeros in the left half of the s-plane.

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6. If the polynomial $P(s)$ and its derivative gives a continued fraction expansion with coefficients, then the polynomial $P(s)$ is Hurwitz.

1. All negative

2. All positive

3. Positive or negative

4. Positive and negative

Show me the answer

Answer: 2) All positive

Explanation: For a polynomial to be Hurwitz (all roots in left half-plane), the continued fraction expansion coefficients must all be positive.

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7. Which of the following device has negative resistance?

1. Gas diode

2. Vacuum diode

3. Tunnel diode

4. None of the above

Show me the answer

Answer: 3) Tunnel diode

Explanation: A tunnel diode exhibits negative resistance region in its I-V characteristic due to quantum tunneling effect.

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8. A MOSFET uses the electric field of a to control the channel current.

1. Capacitor

2. Battery

3. Generator

4. None of the above

Show me the answer

Answer:

1. Capacitor

Explanation: MOSFET operation is based on the electric field created by the gate-source voltage across the gate oxide capacitor, which controls the channel conductivity.

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9. An oscillator produces oscillations due to .......

1. Positive feedback

2. Negative feedback

3. Partly positive and partly negative feedback

4. Neither positive nor negative feedback

Show me the answer

Answer:

1. Positive feedback

Explanation: Oscillators use positive feedback to sustain oscillations by feeding back a portion of output signal in phase with the input.

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10. The noise factor of an ideal amplifier is ...........dB.

1. 0

2. 0.5

3. 5

4. 10

Show me the answer

Answer:

1. 0

Explanation: Noise factor (F) is the ratio of input SNR to output SNR. For an ideal noiseless amplifier, F = 1, which in dB is 0 dB.

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11. Logarithmic amplifiers are used in .......

1. Adders

2. Dividers

3. Multipliers

4. All of the above

Show me the answer

Answer: 3) Multipliers

Explanation: Log amplifiers are used in multiplier circuits by exploiting the property: $\log(A \times B) = \log A + \log B$.

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12. In standard TTL, the 'totem pole' refers to .......

1. Multi-emitter input stage

2. The phase splitter

3. Open collector output stage

4. The output buffer

Show me the answer

Answer: 4) The output buffer

Explanation: Totem-pole output is a push-pull output stage in TTL gates that provides low output impedance and fast switching.

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13. Two's complement of 00011011 is:

1. 11100100

2. 11100101

3. 11000101

4. 11110001

Show me the answer

Answer: 2) 11100101

Explanation: Two's complement is found by inverting bits and adding 1: Invert 00011011 → 11100100 Add 1 → 11100101

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14. Elementary building block of combinational circuit is:

1. Logic gate

2. Flip-flop

3. Both logic gate and flip-flop

4. Memory

Show me the answer

Answer:

1. Logic gate

Explanation: Combinational circuits are built from basic logic gates (AND, OR, NOT, etc.) without memory elements.

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15. Synchronous circuit that changes its state at specific clock signal is:

1. Event driven

2. Clock driven

3. Pulse driven

4. Frequency driven

Show me the answer

Answer: 2) Clock driven

Explanation: Synchronous circuits change state only at the rising or falling edge of a clock signal, making them clock-driven.

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16. Bandwidth of microprocessor represents:

1. Clock speed

2. Width of internal bus

3. Number of bits processed per instruction

4. Number of bits processed per second

Show me the answer

Answer: 3) Number of bits processed per instruction

Explanation: Bandwidth of a microprocessor refers to the data width (e.g., 8-bit, 16-bit) that it can process in one instruction cycle.

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17. PPI 8255 has internal bus of size:

1. 4 bit

2. 8 bit

3. 16 bit

4. 32 bit

Show me the answer

Answer: 2) 8 bit

Explanation: The 8255 Programmable Peripheral Interface has an 8-bit internal data bus for interfacing with 8-bit microprocessors.

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18. RISC is characterized by .......

1. Hardwired control design with no micro codes

2. Fixed instruction format

3. Executing most of the instructions in a single clock cycle

4. All of the above

Show me the answer

Answer: 4) All of the above

Explanation: RISC (Reduced Instruction Set Computer) features include hardwired control, fixed-length instructions, and single-cycle execution for most instructions.

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19. Which among of the following doesn't come under object-oriented programming concept?

1. Data hiding

2. Message passing

3. Platform independent

4. Data binding

Show me the answer

Answer: 3) Platform independent

Explanation: Platform independence is a feature of certain programming languages (like Java) but is not a core OOP concept. OOP concepts are encapsulation, inheritance, polymorphism, etc.

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20. If statement condition is always written in. Parenthesis.

1. Square []

2. Curly {}

3. Angle <>

4. Small ()

Show me the answer

Answer: 4) Small ()

Explanation: In programming languages like C, C++, Java, the condition in an if statement is enclosed in parentheses: if (condition).

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21. Recursive function is similar to

1. Switch case

2. Loop

3. If-else

4. Do loop

Show me the answer

Answer: 2) Loop

Explanation: Recursion and iteration (loops) are two ways to repeat operations. A recursive function calls itself, similar to how a loop repeats a block of code.

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22. In general, the index of the first element in an array is

1. 0

2. -1

3. 2

4. 1

Show me the answer

Answer:

1. 0

Explanation: In most programming languages (C, C++, Java, Python), array indexing starts from 0.

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23. Programmers use when they need to pass a group of related variables.

1. Structure variable

2. Variable

3. Auto variable

4. Constant variable

Show me the answer

Answer:

1. Structure variable

Explanation: A structure allows grouping of related variables of different types under one name, making it easier to pass them as a single entity.

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24. If same message is passed to objects of several different classes and all of those can respond in a different way, this feature is called

1. Inheritance

2. Overloading

3. Polymorphism

4. Over-riding

Show me the answer

Answer: 3) Polymorphism

Explanation: Polymorphism allows objects of different classes to respond differently to the same message or method call.

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25. The static error of an instrument implies the

1. Difference between the measured value and the true value of the quantity

2. Accuracy of the instrument

3. Error introduced in low varying inputs

4. Irreparability of the instrument

Show me the answer

Answer:

1. Difference between the measured value and the true value of the quantity

Explanation: Static error is the deviation of the measured value from the true value under steady-state conditions.

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26. Sensitivity of a sensor can be depicted by

1. Nyquist plot

2. Pole - zero plot

3. Bode plot

4. Box plot

Show me the answer

Answer: 3) Bode plot

Explanation: Bode plot (magnitude vs frequency) shows how the output of a system changes with frequency, indicating sensitivity and frequency response.

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27. In a circuit, an ammeter is always connected in

1. Series

2. Parallel

3. Both parallel and series

4. None of the above

Show me the answer

Answer:

1. Series

Explanation: Ammeter measures current, so it must be connected in series with the load to allow the same current to flow through it.

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28. Which of the following is not a characteristic of an open loop system?

1. It is inaccurate

2. It is economical

3. It has small bandwidth

4. It has feedback elements

Show me the answer

Answer: 4) It has feedback elements

Explanation: Open-loop systems do not have feedback; they operate based solely on the input without correcting for errors.

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29. First order system is defined by

1. Number of poles at origin

2. Order of differential equation

3. Total number of poles of the equation

4. Total number of poles and order of the equation

Show me the answer

Answer: 2) Order of differential equation

Explanation: A first-order system is described by a first-order differential equation in time domain.

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30. Root locus always starts from

1. The open loop poles and terminates at the open loop zeros

2. The open loop zeros and terminates at the open loop poles

3. The close loop poles and terminates at the open loop zeros

4. The close loop poles and terminates at the close loop zeros

Show me the answer

Answer:

1. The open loop poles and terminates at the open loop zeros

Explanation: Root locus starts at open-loop poles (when gain K=0) and ends at open-loop zeros (when K→∞).

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31. In an ideal transformer, the no load primary current $I_0$

1. Lags behind $V_1$ by $90^\circ$

2. Is in phase with $V_1$

3. Leads $V_1$ by $90^\circ$

4. Lags $V_1$ by an angle lying between $0^\circ$ and $90^\circ$

Show me the answer

Answer:

1. Lags behind $V_1$ by $90^\circ$

Explanation: In an ideal transformer under no-load, the primary current is purely magnetizing, which lags the applied voltage by $90^\circ$.

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32. The function of brushes in a DC generator is to

1. Hold the armature winding

2. Provide a low reluctance path for the magnetic flux

3. Convert AC to DC

4. Collect current from the commutator

Show me the answer

Answer: 4) Collect current from the commutator

Explanation: Brushes collect the generated AC current from the commutator segments and deliver it as DC to the external circuit.

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33. The speed of a DC motor can be varied by varying

1. Field current

2. Applied voltage

3. Resistance in series with armature

4. Any of the above

Show me the answer

Answer: 4) Any of the above

Explanation: DC motor speed can be controlled by changing field flux (field current), armature voltage, or armature resistance.

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34. An induction motor is .......

1. Self starting with zero torque

2. Self starting with high torque

3. Self starting with low torque

4. Non-self starting

Show me the answer

Answer: 3) Self starting with low torque

Explanation: Single-phase induction motors are self-starting but produce low starting torque; capacitors or other means are used to improve it.

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35. When the speed of a synchronous generator increases, then

1. The frequency increases

2. The frequency decreases

3. The frequency remains constant but the power factor decreases

4. Power factor and frequency remains constant

Show me the answer

Answer:

1. The frequency increases

Explanation: Frequency of a synchronous generator is directly proportional to its speed: $f = \frac{PN}{120}$.

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36. When any one phase of a 3-phase synchronous motor is short-circuited, the motor .......

1. Will overheat in the spot

2. Will fail to pull into step

3. Will refuse to start

4. Will not come up to speed

Show me the answer

Answer: 3) Will refuse to start

Explanation: A short-circuited phase prevents the production of a rotating magnetic field, so the motor cannot start.

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37. In an analog communication, a unit impulse response of a causal system is ....... for t<0.

1. 0

2. 1

3. Infinite

4. -1

Show me the answer

Answer:

1. 0

Explanation: A causal system’s impulse response $h(t) = 0$ for $t < 0$ (output depends only on present and past inputs).

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38. If the gain crossover frequency of a system is less than its phase cross over frequency, then the system is .......

1. Critically stable

2. Unstable

3. Stable

4. Marginally stable

Show me the answer

Answer: 3) Stable

Explanation: For stability, gain crossover frequency should be less than phase crossover frequency (gain margin > 0 and phase margin > 0).

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39. In inverse DTFT, the limits of the integral is defined between $-π$ to $\pi$ because of the property .......

1. Time invariance

2. Periodicity

3. Implication

4. Convolution

Show me the answer

Answer: 2) Periodicity

Explanation: The Discrete-Time Fourier Transform (DTFT) is periodic with period $2π$, so integration over any interval of length $2π$ suffices.

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40. One-sided z-transform is also known as .......

1. Unilateral z-transform

2. Bilateral z-transform

3. Trilateral z-transform

4. None of the above

Show me the answer

Answer:

1. Unilateral z-transform

Explanation: One-sided z-transform considers only $n ≥ 0$ and is called unilateral z-transform.

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41. What is the stability of the system $s^3 + s^2 + s + 4 = 0$ using Hurwitz criteria?

1. Unstable

2. Stable

3. Critically stable

4. Marginally stable

Show me the answer

Answer:

1. Unstable

Explanation: Apply Routh-Hurwitz: Row1: 1, 1 Row2: 1, 4 Row3: (11 - 14)/1 = -3, 0 Row4: 4 Sign change in first column (1 → -3) indicates unstable system.

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42. The transfer function of FIR filters will have

1. Poles and zeros

2. Only poles

3. Only zeros

4. Only constants

Show me the answer

Answer: 3) Only zeros

Explanation: Finite Impulse Response (FIR) filters have a transfer function with only zeros (all poles are at origin or outside unit circle for stability).

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43. Which modulation is used in microwave band?

1. Amplitude modulation

2. Pulse modulation

3. Frequency modulation

4. Phase modulation

Show me the answer

Answer: 3) Frequency modulation

Explanation: FM is commonly used in microwave communication due to its noise immunity and constant amplitude.

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44. Thermal noise is independent of

1. Boltzmann's constant

2. Temperature

3. Bandwidth

4. Centre frequency

Show me the answer

Answer: 4) Centre frequency

Explanation: Thermal noise power = $kTB$, where k is Boltzmann’s constant, T is temperature, B is bandwidth. It is independent of center frequency.

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45. is mostly preferred for telegraphy.

1. Single tone modulation

2. On-off keying

3. Frequency shift keying

4. Pulse code modulation

Show me the answer

Answer: 2) On-off keying

Explanation: On-off keying (OOK) is a simple form of amplitude shift keying used in traditional telegraphy.

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46. The process of converting the analog sample into discrete form is called

1. Quantization

2. Sampling

3. Multiplexing

4. Modulation

Show me the answer

Answer: 2) Sampling

Explanation: Sampling is the process of converting a continuous-time signal into a discrete-time signal by taking samples at intervals.

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47. Which of the following is not a property of block code?

1. Linearity

2. Systematic

3. Cyclic

4. Non-linearity

Show me the answer

Answer: 4) Non-linearity

Explanation: Block codes are typically linear, systematic, and may be cyclic. Non-linearity is not a standard property of block codes.

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48. The open standard interconnection (OSI) model is a. layer model for the design of network system.

1. Two

2. Five

3. Seven

4. Eight

Show me the answer

Answer: 3) Seven

Explanation: The OSI model has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.

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49. Which of the following pollutant causes acid rain?

1. $NO_2$

2. $SO_2$

3. $CO_2$

Show me the answer

Answer: 2) $SO_2$

Explanation: Sulfur dioxide (SO₂) reacts with water vapor to form sulfuric acid, a major contributor to acid rain.

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50. What is the purpose of impedance matching in transmission lines?

1. To reduce signal reflection

2. To increase signal reflection

3. To reduce signal attenuation

4. To increase signal attenuation

Show me the answer

Answer:

1. To reduce signal reflection

Explanation: Impedance matching minimizes reflections at discontinuities, ensuring maximum power transfer and signal integrity.

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51. The primary function of the fuse is to

1. Open the circuit

2. Protect the appliance

3. Protect the line

4. Prevent excessive current flow through the circuit

Show me the answer

Answer: 4) Prevent excessive current flow through the circuit

Explanation: A fuse melts and opens the circuit when current exceeds a safe limit, protecting the circuit and devices.

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52. Which type of wiring is suitable for multi-storey buildings?

1. Tree system

2. Ring main system

3. Distribution board system

4. Ring main and distribution board system

Show me the answer

Answer: 4) Ring main and distribution board system

Explanation: Multi-storey buildings use a combination of ring main circuits for floors and distribution boards for vertical supply.

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53. Input ripple of SMPS is

1. High

2. Low

3. Nil

4. Very low

Show me the answer

Answer:

1. High

Explanation: Switch-mode power supplies (SMPS) have high-frequency input ripple due to switching action, requiring input filtering.

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54. is a series type unbalanced fault that occurs in a power system.

1. Line to line fault

2. Double line to ground fault

3. Single line to ground fault

4. Open conductor fault

Show me the answer

Answer: 3) Single line to ground fault

Explanation: Single line-to-ground fault is the most common unbalanced fault in power systems.

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55. Standard dimensions $(mm \times mm)$ of A3 drawing sheet is

1. $11.69 \times 16.54$

2. $29.7 \times 42$

3. $297 \times 420$

4. $420 \times 280$

Show me the answer

Answer: 3) $297 \times 420$

Explanation: A3 paper size is 297 mm × 420 mm.

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56. Which of the following methods of charging depreciation of an asset has increased amount of depreciation as the age of asset increases

1. sum-of-year digit

2. sinking fund

3. diminishing balance

4. straight line

Show me the answer

Answer: 3) diminishing balance

Explanation: Diminishing balance method applies a fixed percentage to the reducing book value, resulting in higher depreciation in early years.

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57. The process of optimizing the project's limited resources without extending the project duration is known as

1. project crashing

2. resource levelling

3. resource smoothing

4. networking

Show me the answer

Answer: 3) resource smoothing

Explanation: Resource smoothing adjusts resource allocation within the fixed project duration to avoid peaks and valleys.

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58. The process of composing/raising the required fund from different sources such as equity, preferred stock, bond and debenture is known as

1. capital structure planning

2. project financing

3. capital budgeting decision

4. deducing earning per share

Show me the answer

Answer: 2) project financing

Explanation: Project financing involves raising capital from multiple sources for a specific project.

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59. In which of the following society, people used to seek their existence on growing plants for their cattle and domestic animals

1. pastoral society

2. tribal society

3. horticultural society

4. agricultural society

Show me the answer

Answer: 3) horticultural society

Explanation: Horticultural societies depend on cultivating plants for food and fodder for animals.

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60. According to Nepal Engineering Council Act, 2055 (Revised, 2079), all engineering academic institutions shall be in the Council.

1. affiliated

2. united

3. recognized

4. associated

Show me the answer

Answer: 3) recognized

Explanation: The Act requires engineering institutions to be recognized by the Nepal Engineering Council.

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Long Questions 20*2=40

61. Two equal resistances of resistors are connected in series across a certain supply. If the resistances are now connected in parallel, the power produced will become:

1. one half

2. two times

3. three times

4. four times

Show me the answer

Answer: 4) four times

Explanation: For equal resistances R, series equivalent = 2R, parallel equivalent = R/2. Power P = V²/R. For same V, power ratio = (2R)/(R/2) = 4 times.

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62. For ac circuit, the form factor is the ratio of?

1. average value / r.m.s. value

2. r.m.s. value / average value

3. r.m.s. value / peak value

4. average value / peak value

Show me the answer

Answer: 2) r.m.s. value / average value

Explanation: Form factor = RMS value / Average value.

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63. For the two port network, the condition of symmetry in terms of z-parameters is:

1. $Z_{11} = Z_{22}$

2. $Z_{12} = Z_{21}$

3. $Z_{11} = Z_{21}$

4. $Z_{12} = Z_{22}$

Show me the answer

Answer:

1. $Z_{11} = Z_{22}$

Explanation: A symmetric two-port network satisfies $Z_{11} = Z_{22}$.

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64. The transient current in an RLC circuit is oscillatory when:

1. $R = 0$

2. $R > 2\sqrt{L/C}$

Show me the answer

Answer:

1. $R = 0$

Explanation: Oscillatory response occurs when damping is underdamped: $R < 2\sqrt{L/C}$. For pure oscillation (no damping), R=0.

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65. In an intrinsic semiconductor:

1. only electrons carry current

2. only holes carry current

3. both electrons and holes carry current

4. both electrons and holes carry current with holes being the majority carriers

Show me the answer

Answer: 3) both electrons and holes carry current

Explanation: In intrinsic semiconductors, electrons and holes are equal in number and both contribute to conduction.

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66. JFET is considered as a voltage-controlled device because:

1. drain current is controlled by gate voltage

2. gate current is controlled by drain voltage

3. drain current is controlled by source voltage

4. gate current is controlled by source voltage

Show me the answer

Answer:

1. drain current is controlled by gate voltage

Explanation: In JFET, gate-source voltage controls the channel width and thus the drain current.

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67. In a properly connected BJT, an increase in base current causes increase in:

1. Ic only

2. Ie only

3. Leakage current

4. Both Ic and Ie

Show me the answer

Answer: 4) Both Ic and Ie

Explanation: $I_e = I_c + I_b$, so increasing $I_b$ increases both $I_c$ and $I_e$.

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68. The common mode rejection ration (CMRR) of an ideal OP-Amp is:

1. zero

2. low

3. medium

4. infinite

Show me the answer

Answer: 4) infinite

Explanation: Ideal op-amp rejects common-mode signals completely, so CMRR = ∞.

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69. A half-adder can be constructed from

1. Two XNOR gates only

2. One XOR and one OR gate with their outputs connected in parallel

3. One XOR and one OR gate with their inputs connected in parallel

4. One XOR gate and one AND gate

Show me the answer

Answer: 4) One XOR gate and one AND gate

Explanation: Half-adder: Sum = A ⊕ B, Carry = A · B.

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70. A J-K flip-flop can be made from an R-S flip-flop by using two additional:

1. OR gates

2. AND gates

3. NOR gates

4. NOT gates

Show me the answer

Answer: 2) AND gates

Explanation: J-K flip-flop can be constructed from RS flip-flop with two AND gates feeding the inputs, with feedback from outputs.

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71. A microprocessor has eight data lines and sixteen address lines. The microprocessor is of type:

1. 8 bit

2. 16 bit

3. 20 bit

4. 32 bit

Show me the answer

Answer:

1. 8 bit

Explanation: Data bus width determines bit-size. 8 data lines → 8-bit microprocessor.

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72. Permanent memory of a computer is known as:

1. RAM

2. ROM

3. CD-ROM

4. CPU

Show me the answer

Answer: 2) ROM

Explanation: ROM (Read-Only Memory) is non-volatile, permanent memory.

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73. In a login system, the attempts are allowed up to 3 times. Which type of loop is best suited in this system?

1. for

2. while

3. nested for

4. do while

Show me the answer

Answer:

1. for

Explanation: For loop is ideal when number of iterations is known (3 attempts).

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74. Which programming language is called the mother of programming languages?

1. C

2. C++

3. Java

4. COBOL

Show me the answer

Answer:

1. C

Explanation: C is often called the mother language because many modern languages are influenced by its syntax and structure.

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75. What does the format specifier %10d in printf("%10d",num); do?

1. prints the number in a field of 10 columns

2. prints the number with leading zeros in a field of 10 columns

3. prints only the number without any extra spaces

4. prints the number left-aligned in a field of 10 columns

Show me the answer

Answer:

1. prints the number in a field of 10 columns

Explanation: %10d right-aligns the number in a 10-character wide field.

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76. What is the meaning of the following declaration in C programming language? int(*p)[5]

1. p is a pointer to 5 integers

2. p is a pointer to integer array

3. p is a pointer to an array of 5 integers

4. p is not a pointer

Show me the answer

Answer: 3) p is a pointer to an array of 5 integers

Explanation: int(*p)[5] declares p as a pointer to an array of 5 integers.

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77. A meter reads 125 V and the true value is 125.5 V. What is static error of the instrument?

1. 125 / 0.5 V

2. 125 V

3. 0.5 V

4. 0.5 / 125 V

Show me the answer

Answer: 3) 0.5 V

Explanation: Static error = Measured value - True value = 125 - 125.5 = -0.5 V (magnitude 0.5 V).

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78. Thermo couples are:

1. passive transducers

2. active transducers

3. reactive transducers

4. impedance transducers

Show me the answer

Answer: 2) active transducers

Explanation: Thermocouples generate voltage (emf) in response to temperature difference, so they are active transducers.

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79. Phase margin of a system is used to specify which of the following?

1. Frequency response

2. Absolute stability

3. Time response

Show me the answer

Answer: 2) Absolute stability

Explanation: Phase margin indicates relative stability in frequency domain analysis.

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80. Which is the correct formula for the transfer function of positive feedback?

1. $T = G / (1 - GH)$

2. $T = G / (1 + GH)$

3. $T = H / (1 + GH)$

4. $T = G / (GH)$

Show me the answer

Answer:

1. $T = G / (1 - GH)$

Explanation: For positive feedback, closed-loop transfer function = G/(1 - GH).