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SAIL MCQs

Practice SAIL-oriented Electronics & Telecommunication Engineering MCQs with answers and explanations for technical exam preparation. Questions are arranged in pages of up to 100.

Question 604
Control SystemsRouth-Hurwitz

The Routh-Hurwitz criterion is primarily used to determine?

  • AAbsolute stability without explicitly calculating all roots
  • BOnly steady-state gain
  • COnly system bandwidth
  • DInput signal amplitude
Report an error
Correct Answer: A. Absolute stability without explicitly calculating all roots
Explanation: The Routh-Hurwitz criterion determines how many characteristic roots lie in the right half-plane and hence assesses absolute stability.
Reference: Standard control systems: routh-hurwitz
Question 605
Control SystemsRouth-Hurwitz

For a polynomial with all positive coefficients, positivity of coefficients alone is?

  • AAlways sufficient for stability
  • BNecessary but not generally sufficient for Hurwitz stability
  • CNever relevant
  • DSufficient only for every fourth-order system
Report an error
Correct Answer: B. Necessary but not generally sufficient for Hurwitz stability
Explanation: For a Hurwitz polynomial, coefficients must satisfy necessary sign conditions, but positive coefficients alone do not guarantee all roots lie in the left half-plane.
Reference: Standard control systems: routh-hurwitz
Question 606
Control SystemsSystem Type & Error Constants

The type of a unity-feedback control system is determined by the number of?

  • AZeros at the origin
  • BOpen-loop poles at the origin
  • CClosed-loop poles in the right half-plane
  • DFinite zeros only
Report an error
Correct Answer: B. Open-loop poles at the origin
Explanation: System type equals the number of pure integrators, or poles at s=0, in the open-loop transfer function G(s)H(s).
Reference: Standard control systems: system type & error constants
Question 618
Control SystemsRouth-Hurwitz

At K=6 for s³+2s²+3s+K, the system is at the?

  • AStability boundary
  • BAlways strictly stable
  • CAlways overdamped
  • DOrigin with three repeated poles
Report an error
Correct Answer: A. Stability boundary
Explanation: At K=6, a Routh first-column element becomes zero and a conjugate pair lies on the imaginary axis, marking the stability boundary.
Reference: Standard control systems: routh-hurwitz
Question 620
Control SystemsRoot Locus

Root-locus branches start, for K=0, at the?

  • AOpen-loop poles
  • BOpen-loop zeros
  • CClosed-loop zeros only
  • DImaginary-axis crossings
Report an error
Correct Answer: A. Open-loop poles
Explanation: At zero gain, closed-loop poles coincide with the open-loop poles.
Reference: Standard control systems: root locus
Question 621
Control SystemsRoot Locus

As K approaches infinity, root-locus branches terminate at?

  • AOpen-loop zeros, including zeros at infinity
  • BOpen-loop poles only
  • CThe origin only
  • DThe positive real axis only
Report an error
Correct Answer: A. Open-loop zeros, including zeros at infinity
Explanation: Branches end at finite open-loop zeros; if there are more poles than finite zeros, the remaining branches terminate at zeros at infinity.
Reference: Standard control systems: root locus
Question 622
Control SystemsRoot Locus

The number of root-locus branches equals the number of?

  • AOpen-loop poles
  • BOpen-loop finite zeros only
  • CClosed-loop zeros
  • DBreakaway points
Report an error
Correct Answer: A. Open-loop poles
Explanation: Each open-loop pole is the starting point of one root-locus branch.
Reference: Standard control systems: root locus
Question 624
Control SystemsRoot Locus

The centroid of root-locus asymptotes is located at?

  • A(sum of poles - sum of zeros)/(n-m)
  • B(sum of poles + sum of zeros)/(n+m)
  • CProduct of poles divided by product of zeros
  • DOrigin in every system
Report an error
Correct Answer: A. (sum of poles - sum of zeros)/(n-m)
Explanation: For n>m, the asymptote centroid is σa=(Σpoles-Σzeros)/(n-m).
Reference: Standard control systems: root locus
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Question 636
Control SystemsStability Margins

Phase margin is measured at the?

  • AGain crossover frequency
  • BPhase crossover frequency only
  • CNatural frequency always
  • DDC frequency only
Report an error
Correct Answer: A. Gain crossover frequency
Explanation: Phase margin is the additional phase lag needed to reach -180° at the gain crossover frequency.
Reference: Standard control systems: stability margins
Question 637
Control SystemsStability Margins

Gain margin is evaluated at the?

  • AGain crossover frequency
  • BPhase crossover frequency
  • CResonant frequency only
  • DSampling frequency
Report an error
Correct Answer: B. Phase crossover frequency
Explanation: Gain margin is determined from the loop magnitude at the phase crossover frequency.
Reference: Standard control systems: stability margins
Question 642
Control SystemsNyquist Stability

If an open-loop transfer function has no right-half-plane poles, closed-loop stability under the standard Nyquist criterion requires the Nyquist plot to have?

  • ANo encirclement of -1+j0
  • BOne clockwise encirclement of -1+j0
  • COne counterclockwise encirclement always
  • DAn encirclement of the origin
Report an error
Correct Answer: A. No encirclement of -1+j0
Explanation: When P=0, closed-loop stability requires Z=0; under the standard convention this means no net encirclement of the -1 point.
Reference: Standard control systems: nyquist stability
Question 643
Control SystemsNyquist Stability

The Nyquist plot is a mapping of a contour from the?

  • As-plane through the loop transfer function
  • BTime domain directly into the z-plane only
  • COutput plane into the input plane
  • DRoot locus into the Routh array
Report an error
Correct Answer: A. s-plane through the loop transfer function
Explanation: Nyquist analysis maps the Nyquist contour in the s-plane through the loop transfer function L(s)=G(s)H(s).
Reference: Standard control systems: nyquist stability
Question 644
Control SystemsFrequency Response

For a minimum-phase stable loop, larger positive phase margin generally indicates?

  • AGreater relative stability and damping tendency
  • BGuaranteed instability
  • CZero bandwidth
  • DInfinite steady-state error
Report an error
Correct Answer: A. Greater relative stability and damping tendency
Explanation: Within ordinary design tradeoffs, a larger positive phase margin generally corresponds to greater relative stability and a more damped closed-loop response.
Reference: Standard control systems: frequency response
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Question 651
Control SystemsControllers

A proportional controller primarily has control law?

  • Au(t)=Kp e(t)
  • Bu(t)=Ki∫e(t)dt only
  • Cu(t)=Kd de(t)/dt only
  • Du(t)=0
Report an error
Correct Answer: A. u(t)=Kp e(t)
Explanation: A P controller produces control effort proportional to the instantaneous error.
Reference: Standard control systems: controllers
Question 652
Control SystemsControllers

Integral control is particularly useful for reducing or eliminating?

  • ASteady-state error for suitable stable systems
  • BAll measurement noise
  • CPlant order
  • DEvery transient oscillation
Report an error
Correct Answer: A. Steady-state error for suitable stable systems
Explanation: Integral action accumulates error and increases low-frequency loop gain, often eliminating steady-state error to constant inputs when the resulting closed loop is stable.
Reference: Standard control systems: controllers
Question 653
Control SystemsControllers

Derivative control responds to?

  • AThe rate of change of error
  • BOnly accumulated error
  • COnly constant error magnitude
  • DThe reference amplitude squared
Report an error
Correct Answer: A. The rate of change of error
Explanation: Derivative action is proportional to de(t)/dt and anticipates changes in error.
Reference: Standard control systems: controllers
Question 654
Control SystemsControllers

The transfer function of an ideal PID controller is?

  • AKp+Ki/s+Kd s
  • BKp s+Ki+Kd/s²
  • CKp/(s+1) only
  • DKi s only
Report an error
Correct Answer: A. Kp+Ki/s+Kd s
Explanation: An ideal PID controller combines proportional, integral and derivative actions: Gc(s)=Kp+Ki/s+Kd s.
Reference: Standard control systems: controllers
Question 656
Control SystemsCompensators

A phase-lead compensator is commonly used to improve?

  • APhase margin and transient response
  • BSteady-state error only with no transient effect
  • CSensor noise generation
  • DSystem type by two automatically
Report an error
Correct Answer: A. Phase margin and transient response
Explanation: Lead compensation adds positive phase over a frequency range and is commonly used to improve phase margin, bandwidth and transient response.
Reference: Standard control systems: compensators
Question 657
Control SystemsCompensators

A phase-lag compensator is commonly used mainly to improve?

  • ASteady-state accuracy by increasing low-frequency gain
  • BHigh-frequency noise amplification
  • CNatural frequency to infinity
  • DPhase lead at all frequencies
Report an error
Correct Answer: A. Steady-state accuracy by increasing low-frequency gain
Explanation: Lag compensation can raise effective low-frequency loop gain relative to high-frequency gain, improving steady-state accuracy with modest transient impact.
Reference: Standard control systems: compensators
Question 658
Control SystemsCompensators

A lead compensator typically has its zero located?

  • ACloser to the origin than its pole on the negative real axis
  • BFarther from the origin than its pole
  • CAt exactly the same location as its pole
  • DIn the right half-plane necessarily
Report an error
Correct Answer: A. Closer to the origin than its pole on the negative real axis
Explanation: A standard lead network has a zero at a lower break frequency than its pole, so the zero lies closer to the origin on the negative real axis.
Reference: Standard control systems: compensators
Question 665
Control SystemsState Space

The observability matrix for an n-state system begins as?

  • A[C; CA; CA²; ...; CA^(n-1)]
  • B[B; AB; A²B; ...]
  • C[A; B; C]
  • D[D; CD] only
Report an error
Correct Answer: A. [C; CA; CA²; ...; CA^(n-1)]
Explanation: The standard observability matrix is formed by stacking C, CA, CA², ..., CA^(n-1).
Reference: Standard control systems: state space
Question 667
Control SystemsState Space

For the state matrix A=diag(-2,-5), the system poles are?

  • A2 and 5
  • B-2 and -5
  • C-7 and 10
  • D0 and -10
Report an error
Correct Answer: B. -2 and -5
Explanation: The eigenvalues of a diagonal matrix are its diagonal entries, so the poles are -2 and -5.
Reference: Standard control systems: state space
Question 670
Control SystemsState Space

The eigenvalues of the state matrix A correspond to the system’s?

  • APoles for a minimal state-space realization
  • BZeros only
  • CInput frequencies only
  • DStatic error constants
Report an error
Correct Answer: A. Poles for a minimal state-space realization
Explanation: For a minimal realization, eigenvalues of A are the system poles.
Reference: Standard control systems: state space
Question 671
Control SystemsState Space

A continuous-time state-space system x_dot=Ax is asymptotically stable if all eigenvalues of A have?

  • AStrictly negative real parts
  • BStrictly positive real parts
  • CZero real parts only
  • DMagnitude greater than one
Report an error
Correct Answer: A. Strictly negative real parts
Explanation: For a finite-dimensional continuous-time LTI system, asymptotic stability requires all eigenvalues of A to lie strictly in the left half-plane.
Reference: Standard control systems: state space
Question 673
Microprocessors & MicrocontrollersFundamentals

A microprocessor is primarily a?

  • ACPU implemented on an integrated circuit
  • BComplete power supply
  • CMechanical switching device
  • DMemory-only device
Report an error
Correct Answer: A. CPU implemented on an integrated circuit
Explanation: A microprocessor integrates the central processing unit functions on an IC and normally requires external memory and peripherals.
Reference: Standard microprocessors and microcontrollers: fundamentals
Question 674
Microprocessors & MicrocontrollersFundamentals

A microcontroller typically integrates which elements on a single chip?

  • ACPU, memory and peripheral interfaces
  • BOnly an ALU
  • COnly RAM
  • DOnly a clock generator
Report an error
Correct Answer: A. CPU, memory and peripheral interfaces
Explanation: A microcontroller commonly combines CPU, program/data memory and peripherals such as I/O ports and timers on one chip.
Reference: Standard microprocessors and microcontrollers: fundamentals
Question 675
Microprocessors & MicrocontrollersCPU Architecture

The ALU in a processor is mainly responsible for?

  • AArithmetic and logical operations
  • BLong-term program storage only
  • CGenerating AC power
  • DMechanical input switching
Report an error
Correct Answer: A. Arithmetic and logical operations
Explanation: The arithmetic logic unit performs operations such as addition, subtraction, AND, OR and comparisons.
Reference: Standard microprocessors and microcontrollers: cpu architecture
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Question 676
Microprocessors & MicrocontrollersCPU Architecture

The program counter normally contains?

  • AAddress of the next instruction to be fetched
  • BCurrent arithmetic result
  • CStack data only
  • DPower-supply voltage
Report an error
Correct Answer: A. Address of the next instruction to be fetched
Explanation: The program counter tracks the address from which the next instruction is to be fetched.
Reference: Standard microprocessors and microcontrollers: cpu architecture
Question 677
Microprocessors & MicrocontrollersCPU Architecture

The stack pointer is used to?

  • APoint to the current top of the stack
  • BStore every opcode permanently
  • CGenerate clock frequency
  • DCount address lines
Report an error
Correct Answer: A. Point to the current top of the stack
Explanation: The stack pointer holds an address associated with the top of the processor's stack.
Reference: Standard microprocessors and microcontrollers: cpu architecture
Question 678
Microprocessors & MicrocontrollersCPU Architecture

A processor register is generally?

  • AA small high-speed storage location inside the CPU
  • BAn external hard disk
  • CA mechanical relay
  • DA power amplifier
Report an error
Correct Answer: A. A small high-speed storage location inside the CPU
Explanation: Registers are fast storage locations within the processor used for operands, addresses and intermediate results.
Reference: Standard microprocessors and microcontrollers: cpu architecture
Question 679
Microprocessors & Microcontrollers8085 Basics

The 8085 is fundamentally an?

  • A8-bit microprocessor
  • B16-bit microcontroller
  • C32-bit DSP only
  • D4-bit memory chip
Report an error
Correct Answer: A. 8-bit microprocessor
Explanation: The Intel 8085 is classified as an 8-bit microprocessor because its main data operations and data bus are 8 bits wide.
Reference: Standard microprocessors and microcontrollers: 8085 basics
Question 680
Microprocessors & Microcontrollers8085 Basics

The 8085 has an address bus of?

  • A8 bits
  • B12 bits
  • C16 bits
  • D20 bits
Report an error
Correct Answer: C. 16 bits
Explanation: The 8085 provides 16 address lines, allowing 2^16 addressable byte locations.
Reference: Standard microprocessors and microcontrollers: 8085 basics
Question 682
Microprocessors & Microcontrollers8085 Basics

The 8085 data bus width is?

  • A4 bits
  • B8 bits
  • C16 bits
  • D20 bits
Report an error
Correct Answer: B. 8 bits
Explanation: The 8085 has an 8-bit bidirectional data bus.
Reference: Standard microprocessors and microcontrollers: 8085 basics
Question 684
Microprocessors & Microcontrollers8085 Registers

In the 8085, the accumulator is an?

  • A8-bit register
  • B16-bit register
  • C20-bit register
  • D1-bit register
Report an error
Correct Answer: A. 8-bit register
Explanation: The 8085 accumulator A is an 8-bit register used extensively by arithmetic and logic instructions.
Reference: Standard microprocessors and microcontrollers: 8085 registers
Question 685
Microprocessors & Microcontrollers8085 Flags

Which of the following is an 8085 flag?

  • AZero flag
  • BDMA flag
  • CUSB flag
  • DEthernet flag
Report an error
Correct Answer: A. Zero flag
Explanation: The 8085 flag register includes Sign, Zero, Auxiliary Carry, Parity and Carry flags.
Reference: Standard microprocessors and microcontrollers: 8085 flags
Question 687
Microprocessors & Microcontrollers8085 Flags

The Carry flag in the 8085 is particularly used to indicate?

  • ACarry out or borrow condition associated with arithmetic
  • BInstruction address only
  • CClock failure
  • DMemory refresh only
Report an error
Correct Answer: A. Carry out or borrow condition associated with arithmetic
Explanation: The Carry flag records carry/borrow information from arithmetic operations and is also affected by certain rotate operations.
Reference: Standard microprocessors and microcontrollers: 8085 flags
Question 688
Microprocessors & Microcontrollers8085 Instructions

The instruction MOV B,C in the 8085 performs what operation?

  • ACopies contents of C into B
  • BCopies B into C
  • CAdds B and C
  • DClears both B and C
Report an error
Correct Answer: A. Copies contents of C into B
Explanation: The 8085 MOV destination,source format copies the source operand into the destination, so B receives C.
Reference: Standard microprocessors and microcontrollers: 8085 instructions
Question 690
Microprocessors & MicrocontrollersCPU Architecture

The accumulator in many classic microprocessors is mainly used to?

  • AHold operands and arithmetic/logic results
  • BStore the entire operating system
  • CGenerate address-bus timing only
  • DReplace ROM permanently
Report an error
Correct Answer: A. Hold operands and arithmetic/logic results
Explanation: The accumulator is a central register used by many arithmetic and logic instructions.
Reference: Standard microprocessors and microcontrollers: cpu architecture
Question 692
Microprocessors & MicrocontrollersBus Organization

The address bus is normally used to carry?

  • AAddresses of memory or I/O locations
  • BOnly arithmetic results
  • CClock pulses only
  • DPower to peripherals
Report an error
Correct Answer: A. Addresses of memory or I/O locations
Explanation: The address bus identifies the memory or I/O location involved in a transfer.
Reference: Standard microprocessors and microcontrollers: bus organization
Question 693
Microprocessors & Microcontrollers8085 Instructions

The 8085 JMP instruction is used for?

  • AUnconditional transfer of program control to a specified address
  • BAddition of two registers
  • CLoading immediate data into the accumulator
  • DReturning from a subroutine
Report an error
Correct Answer: A. Unconditional transfer of program control to a specified address
Explanation: JMP address loads the program counter with the specified target address without testing a condition.
Reference: Standard microprocessors and microcontrollers: 8085 instructions
Question 694
Microprocessors & MicrocontrollersBus Organization

The data bus carries?

  • AData between processor, memory and peripherals
  • BOnly addresses
  • COnly reset signals
  • DOnly interrupt priorities
Report an error
Correct Answer: A. Data between processor, memory and peripherals
Explanation: The data bus transfers instruction bytes and data among system components.
Reference: Standard microprocessors and microcontrollers: bus organization
Question 695
Microprocessors & Microcontrollers8085 Instructions

The 8085 CALL instruction is primarily used to?

  • AInvoke a subroutine while saving the return address
  • BClear all registers
  • CDisable the clock
  • DPerform multiplication directly
Report an error
Correct Answer: A. Invoke a subroutine while saving the return address
Explanation: CALL transfers control to a subroutine and saves the return address on the stack so execution can later resume after a RET.
Reference: Standard microprocessors and microcontrollers: 8085 instructions
Question 698
Microprocessors & Microcontrollers8085 Addressing Modes

Which addressing mode is used by the 8085 instruction LDA 2050H?

  • ARegister
  • BImmediate
  • CDirect
  • DImplied
Report an error
Correct Answer: C. Direct
Explanation: LDA contains the 16-bit memory address of the operand explicitly, so it uses direct addressing.
Reference: Standard microprocessors and microcontrollers: 8085 addressing modes
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