ETC EngineeringMCQs
Home › Exam MCQs › RRB

RRB MCQs

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

Question 1602
Network TheoryNetwork Topology

A fundamental loop is formed when?

  • AOne link is added to a tree
  • BOne twig is removed from every graph
  • CAll nodes are shorted together
  • DAll voltage sources are opened
Report an error
Correct Answer: A. One link is added to a tree
Explanation: A tree contains no closed path. Adding any one link to it creates exactly one fundamental loop.
Reference: Standard network theory: fundamental loops
Question 1609
Network TheoryPower Factor Correction

Improving a lagging load power factor by connecting a shunt capacitor primarily reduces the source?

  • AReactive current component
  • BReal power demanded by the load to zero
  • CSupply frequency
  • DLoad resistance to zero
Report an error
Correct Answer: A. Reactive current component
Explanation: The capacitor supplies leading reactive current locally, reducing the lagging reactive current drawn from the source while the load real-power requirement is essentially unchanged.
Reference: Standard network theory: power factor correction
Question 1610
Network TheoryPower Factor Correction

A 1 kW load operates at 0.8 lagging power factor. The reactive power is approximately 0.75 kVAR. To correct the power factor ideally to unity, the shunt capacitor bank should supply approximately?

  • A0.25 kVAR leading
  • B0.5 kVAR leading
  • C0.75 kVAR leading
  • D1.25 kVAR leading
Report an error
Correct Answer: C. 0.75 kVAR leading
Explanation: Unity power factor requires cancellation of the load's lagging reactive power, so the capacitor should provide about 0.75 kVAR leading.
Reference: Standard network theory: reactive compensation
Question 1611
Network TheoryNetwork Theorems

Tellegen’s theorem is fundamentally based on conservation of?

  • APower in a network satisfying KCL and KVL
  • BResistance only
  • CFrequency only
  • DMagnetic flux only
Report an error
Correct Answer: A. Power in a network satisfying KCL and KVL
Explanation: Tellegen's theorem states that the algebraic sum of instantaneous branch powers is zero for networks whose branch voltages and currents satisfy KVL and KCL.
Reference: Standard network theory: Tellegen theorem
Question 1612
Network TheoryNetwork Theorems

The reciprocity theorem is applicable to a linear bilateral network containing a single independent source when comparing?

  • AInterchanged excitation and response locations
  • BOnly total resistance with all sources removed
  • COnly nonlinear diode currents
  • DOnly transient initial conditions
Report an error
Correct Answer: A. Interchanged excitation and response locations
Explanation: Reciprocity states, under its applicable conditions, that interchanging the location of excitation and measured response gives the same transfer relationship.
Reference: Standard network theory: reciprocity theorem
Question 1613
Network TheoryNetwork Theorems

Millman’s theorem is particularly convenient for finding the voltage at a node connected to several parallel branches containing?

  • AVoltage sources with series impedances
  • BOnly ideal inductors in series
  • COnly dependent current sources with no impedance
  • DA single resistor only
Report an error
Correct Answer: A. Voltage sources with series impedances
Explanation: Millman's theorem combines multiple parallel source-impedance branches into a direct weighted expression for the common node voltage.
Reference: Standard network theory: Millman theorem
Question 1614
Network TheoryNetwork Theorems

Two parallel branches connect a node to ground. Branch 1 has a 10 V source in series with 5 ohm and branch 2 has a 5 V source in series with 5 ohm, with both source polarities tending to make the node positive. By Millman’s theorem, the node voltage is?

  • A2.5 V
  • B5 V
  • C7.5 V
  • D15 V
Report an error
Correct Answer: C. 7.5 V
Explanation: V=(10/5+5/5)/(1/5+1/5)=3/0.4=7.5 V.
Reference: Standard network theory: Millman theorem numerical
Question 1622
Network TheoryNetwork Synthesis

For a physically realizable passive driving-point impedance, a necessary network-synthesis property is that the function be?

  • APositive real
  • BPurely negative real at all frequencies
  • CAn arbitrary non-rational function
  • DUnstable by definition
Report an error
Correct Answer: A. Positive real
Explanation: Driving-point immittance functions of passive RLC networks must satisfy positive-real conditions, including nonnegative real part in the right-half-plane where defined.
Reference: Standard network theory: positive-real functions
Question 1623
Network TheoryNetwork Synthesis

A real-rational function F(s) is called positive real if, among other requirements, Re[F(s)] is?

  • ANonnegative for Re(s)>0
  • BAlways negative for Re(s)>0
  • CZero for every complex s
  • DInfinite on the entire j-omega axis
Report an error
Correct Answer: A. Nonnegative for Re(s)>0
Explanation: One defining condition of a positive-real function is Re[F(s)]>=0 in the open right-half s-plane, together with appropriate real-rational symmetry conditions.
Reference: Standard network theory: positive-real condition
Question 1624
Network TheoryNodal Analysis

In modified nodal analysis, an ideal voltage source connected between two non-reference nodes is commonly handled by introducing?

  • AAn additional source-current unknown and a voltage constraint equation
  • BAn open circuit in every case
  • CA short circuit in every case
  • DOnly a mesh-current equation with no node voltages
Report an error
Correct Answer: A. An additional source-current unknown and a voltage constraint equation
Explanation: Modified nodal analysis augments the node-voltage equations with an unknown current through the voltage source and an equation enforcing the source voltage.
Reference: Standard network theory: modified nodal analysis
Question 1625
Network TheoryNodal Analysis

A supernode is formed in nodal analysis when an ideal voltage source is connected between?

  • ATwo non-reference nodes
  • BA node and a resistor only
  • CTwo current sources in series
  • DTwo reference nodes only
Report an error
Correct Answer: A. Two non-reference nodes
Explanation: A voltage source between two unknown-voltage nodes prevents direct branch-current expression by conductance, so the two nodes are treated together as a supernode.
Reference: Standard network theory: supernode
Advertisement / responsive in-content slot
Question 1627
Network TheoryMesh Analysis

A supermesh is used in mesh analysis when an ideal current source lies in a branch common to?

  • ATwo adjacent meshes
  • BA mesh and the reference node only
  • CTwo voltage sources in parallel
  • DTwo resistors in series only
Report an error
Correct Answer: A. Two adjacent meshes
Explanation: A current source shared by adjacent meshes prevents writing an ordinary KVL equation through that branch, so the surrounding meshes are combined into a supermesh.
Reference: Standard network theory: supermesh
Question 1629
Network TheoryNetwork Functions

For a linear network, the driving-point impedance at a port is defined as?

  • AVoltage at the port divided by current entering the same port
  • BCurrent at one port divided by voltage at another port
  • COutput power divided by input voltage
  • DVoltage multiplied by current
Report an error
Correct Answer: A. Voltage at the port divided by current entering the same port
Explanation: A driving-point impedance relates voltage and current at the same pair of terminals: Z(s)=V(s)/I(s).
Reference: Standard network theory: driving-point impedance
Question 1630
Network TheoryNetwork Functions

A transfer impedance network function is generally defined as?

  • AOutput voltage divided by input current
  • BInput voltage divided by input current at the same port only
  • COutput current divided by output voltage
  • DInput power divided by output power
Report an error
Correct Answer: A. Output voltage divided by input current
Explanation: Transfer impedance, or transimpedance, relates a response voltage at one location to an excitation current at another: Zt(s)=Vout(s)/Iin(s).
Reference: Standard network theory: transfer impedance
Question 1631
Network TheoryNetwork Functions

A transfer admittance is generally expressed as?

  • AOutput current divided by input voltage
  • BOutput voltage divided by input current
  • CInput voltage divided by input current
  • DOutput voltage divided by output current
Report an error
Correct Answer: A. Output current divided by input voltage
Explanation: Transfer admittance relates response current to excitation voltage, typically Yt(s)=Iout(s)/Vin(s).
Reference: Standard network theory: transfer admittance
Question 1632
Network TheoryNetwork Synthesis

In a lossless LC driving-point reactance function, poles and zeros on the j-omega axis characteristically?

  • AInterlace
  • BAlways coincide
  • COccur only at positive real s
  • DHave no ordering relationship
Report an error
Correct Answer: A. Interlace
Explanation: For realizable LC reactance functions, simple poles and zeros lie on the imaginary axis and alternate, or interlace, with frequency.
Reference: Standard network theory: reactance functions
Question 1633
Network TheoryNetwork Synthesis

Foster’s first form for an LC driving-point impedance is obtained from a partial-fraction expansion of?

  • AThe impedance function Z(s)
  • BOnly the time-domain current
  • CThe incidence matrix
  • DThe nodal determinant only
Report an error
Correct Answer: A. The impedance function Z(s)
Explanation: Foster-I impedance realization follows directly from expanding Z(s) into partial fractions, with terms represented by simple reactive sections.
Reference: Standard network theory: Foster realization
Question 1634
Network TheoryNetwork Synthesis

Cauer network synthesis is based primarily on?

  • AContinued-fraction expansion
  • BFourier-series expansion
  • CTaylor expansion around infinity only
  • DMatrix inversion without a network function
Report an error
Correct Answer: A. Continued-fraction expansion
Explanation: Cauer forms are ladder realizations derived by successive continued-fraction expansion of a driving-point impedance or admittance.
Reference: Standard network theory: Cauer realization
Question 1640
Network TheoryTwo-Port Networks

The h-parameter h11 of a two-port is an input impedance measured with?

  • AOutput port short-circuited
  • BOutput port open-circuited
  • CInput port open-circuited
  • DBoth ports disconnected
Report an error
Correct Answer: A. Output port short-circuited
Explanation: From V1=h11 I1+h12 V2, setting V2=0 corresponds to an output short circuit, so h11=V1/I1 under that condition.
Reference: Standard network theory: h-parameters
Question 1641
Network TheoryTwo-Port Networks

The h-parameter h22 is an output admittance measured with?

  • AInput port open-circuited
  • BInput port short-circuited
  • COutput port open-circuited
  • DBoth port currents zero
Report an error
Correct Answer: A. Input port open-circuited
Explanation: From I2=h21 I1+h22 V2, setting I1=0 means the input port is open, so h22=I2/V2 under that condition.
Reference: Standard network theory: h-parameters
Advertisement / responsive in-content slot
Question 1664
Network TheoryLaplace Transform

The Laplace transform of t for t>=0 is?

  • A1/s
  • B1/s^2
  • Cs
  • Ds^2
Report an error
Correct Answer: B. 1/s^2
Explanation: Using L{t^n}=n!/s^(n+1), for n=1 the transform is 1/s^2.
Reference: Standard network theory: transform of ramp
Question 1668
Network TheoryNetwork Functions

A stable causal rational network function requires all natural-response poles to lie where in the s-plane?

  • AOpen right-half plane
  • BOpen left-half plane
  • COnly at the origin
  • DAnywhere on the real axis
Report an error
Correct Answer: B. Open left-half plane
Explanation: For asymptotic stability of a causal continuous-time rational network, natural modes must decay, requiring poles in the open left-half plane.
Reference: Standard network theory: stability and poles
Question 1674
Network TheoryTwo-Port Networks

A transmission line section represented by ABCD parameters has A=2, B=3 ohm, C=1 siemens and D=2. Is it reciprocal?

  • AYes, because AD-BC=1
  • BNo, because AD-BC=7
  • CYes, because A=D
  • DNo, because B is not equal to C
Report an error
Correct Answer: A. Yes, because AD-BC=1
Explanation: For reciprocity, AD-BC must equal 1. Here 2×2-3×1=1, so the network satisfies the reciprocity condition.
Reference: Standard network theory: ABCD reciprocity numerical
Question 1675
Network TheoryTwo-Port Networks

When two two-port networks are connected in parallel at both ports, which parameter matrices are especially convenient to add directly?

  • Az-parameters
  • By-parameters
  • CABCD parameters
  • Dh-parameters only
Report an error
Correct Answer: B. y-parameters
Explanation: For parallel-connected two-ports, corresponding port voltages are common and currents add, making admittance or y-parameters convenient.
Reference: Standard network theory: parallel two-port connection
Advertisement / responsive in-content slot
Question 1676
Network TheoryTwo-Port Networks

When two two-port networks are connected in series at both ports, which parameter matrices are especially convenient to add directly?

  • Az-parameters
  • By-parameters
  • CABCD parameters
  • DS-parameters only
Report an error
Correct Answer: A. z-parameters
Explanation: In a series-series interconnection, port currents are common and voltages add, so impedance or z-parameter matrices add directly.
Reference: Standard network theory: series two-port connection
Question 1677
Network TheoryTwo-Port Networks

For two cascaded two-port networks, which representation is normally the most convenient because the overall matrix is obtained by ordered multiplication?

  • Az-parameters
  • By-parameters
  • CABCD parameters
  • Dg-parameters
Report an error
Correct Answer: C. ABCD parameters
Explanation: Transmission or ABCD matrices multiply directly in cascade order, which makes them convenient for cascaded networks.
Reference: Standard network theory: cascaded two-port representation
Question 1681
Network TheoryCoupled Circuits

If the dot convention shows current entering the dotted terminal of coil 1 and the mutually induced voltage of coil 2 is referenced positive at its dotted terminal, the mutual-voltage term is taken as?

  • A+M di1/dt
  • B-M di1/dt
  • CZero for all coupling
  • DM/i1
Report an error
Correct Answer: A. +M di1/dt
Explanation: With the stated dot-reference convention, current entering a dotted terminal induces a voltage positive at the dotted terminal of the other coil, giving a positive mutual term.
Reference: Standard network theory: dot convention
Question 1684
Network TheoryNetwork Functions

A network function H(s)=(s+3)/(s^2+5s+6) has poles at?

  • A-1 and -6
  • B-2 and -3
  • C+2 and +3
  • D-3 only
Report an error
Correct Answer: B. -2 and -3
Explanation: The denominator factors as (s+2)(s+3), so the poles are at s=-2 and s=-3.
Reference: Standard network theory: pole calculation
Question 1686
Network TheoryNetwork Functions

A rational network function is strictly proper when?

  • ADegree of numerator is less than degree of denominator
  • BDegree of numerator equals degree of denominator
  • CDegree of numerator is greater than degree of denominator
  • DIts denominator is a constant
Report an error
Correct Answer: A. Degree of numerator is less than degree of denominator
Explanation: A strictly proper rational function has numerator degree lower than denominator degree, so its magnitude tends to zero as |s| tends to infinity.
Reference: Standard network theory: proper network functions
Question 1688
Network TheoryNetwork Functions

The impulse response of a causal LTI network is obtained from its transfer function H(s) by?

  • ATaking the inverse Laplace transform of H(s)
  • BDifferentiating H(s) only with respect to resistance
  • CSetting s=0 only
  • DTaking the square of H(s)
Report an error
Correct Answer: A. Taking the inverse Laplace transform of H(s)
Explanation: For zero initial conditions, the causal impulse response h(t) is the inverse Laplace transform of H(s).
Reference: Standard network theory: impulse response
Question 1689
Network TheoryNetwork Functions

If H(s)=1/(s+4), the causal impulse response is?

  • Ae^(-4t)u(t)
  • B4e^(-t)u(t)
  • C1-e^(-4t)
  • Ddelta(t-4)
Report an error
Correct Answer: A. e^(-4t)u(t)
Explanation: The inverse Laplace transform of 1/(s+a) is e^(-at)u(t), so h(t)=e^(-4t)u(t).
Reference: Standard network theory: impulse response numerical
Question 1698
Network TheoryNetwork Topology

For an oriented graph, each column of the node-branch incidence matrix corresponding to an ordinary branch contains?

  • AOne +1 and one -1
  • BTwo +1 entries only
  • COne nonzero entry only
  • DAll zero entries
Report an error
Correct Answer: A. One +1 and one -1
Explanation: An oriented branch leaves one node and enters another, so its incidence-matrix column has one +1 and one -1 under a consistent sign convention.
Reference: Standard network theory: incidence matrix structure
Question 1700
Network TheoryNetwork Topology

A tie-set matrix is primarily used to express branch currents in terms of?

  • AIndependent loop currents
  • BNode voltages only
  • CBranch powers
  • DCut-set voltages only
Report an error
Correct Answer: A. Independent loop currents
Explanation: Tie-set or fundamental-loop analysis relates branch currents to a set of independent loop currents.
Reference: Standard network theory: tie-set matrix
Advertisement / responsive in-content slot