In a DC generator, the commutator serves the purpose of:

The correct answer is B: Converting AC induced EMF to DC. The commutator rectifies the alternating EMF induced in the armature coils to produce unidirectional (DC) output.

The sensitivity of a galvanometer is defined as:

The correct answer is A: Deflection per unit current. Sensitivity of a galvanometer is the deflection (in mm or degrees) produced per unit current (usually per microampere or milliampere).

A capacitor with capacitance C = 50μF is charged to 200V. What is the energy stored in the capacitor?

The correct answer is B: 1J. Energy stored E = ½CV² = ½ × 50×10⁻⁶ × (200)² = ½ × 50×10⁻⁶ × 40000 = 1J

Which of the following is a state-space representation advantage over transfer function?

The correct answer is B: Can handle multiple inputs and outputs (MIMO systems). State-space representation naturally handles MIMO systems, non-linear systems, and time-varying systems better than transfer functions.

The static error constant for a Type-1 system with G(s) = 20/(s(s+5)(s+10)) is:

The correct answer is A: 0.4. For Type-1 system, Kv = lim s→0 s·G(s) = 20/(5·10) = 20/50 = 0.4

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Electrical Engg (EEE)

Electrical machines, power systems, circuits

123 Q 7 Topics Take Mock Test

Difficulty: All Easy Medium Hard 51–60 of 123

Topics in Electrical Engg (EEE)

All Circuit Analysis 100 Electrical Machines 100 Power Systems 100 Control Systems 100 Power Electronics 100 Electrical Measurements 40 Digital Electronics 100

Q.51 Hard Power Electronics

Which of the following has the lowest on-state voltage drop among power semiconductor devices?

A Power Diode

B MOSFET

C IGBT

D SCR

Correct Answer: B. MOSFET

EXPLANATION

MOSFETs have the lowest on-state voltage drop (few hundred millivolts) at moderate currents. IGBTs: ~1-2V, SCRs: ~1-2V, Diodes: ~0.7-1V depending on rating.

Test

Q.52 Hard Power Electronics

In a three-phase inverter, 180° conduction mode means:

A Each switch conducts for 180° of the fundamental cycle

B Output frequency is doubled

C All switches conduct simultaneously

D Output voltage is sinusoidal

Correct Answer: A. Each switch conducts for 180° of the fundamental cycle

EXPLANATION

In 180° conduction, each switch conducts for half the fundamental cycle (180°), typically producing a 6-step output. 120° conduction has each switch on for 120° only.

Test

Q.53 Hard Control Systems

In a Type-2 system with step, ramp, and parabolic inputs, the steady-state error with parabolic input A·t²/2 and loop gain Kv = 5 is:

A Zero

B A/Kv

C A/Ka where Ka is the acceleration error constant

D Infinity

Correct Answer: C. A/Ka where Ka is the acceleration error constant

EXPLANATION

For a Type-2 system, parabolic error is ess = A/Ka where Ka = lim[s→0] s²G(s)H(s). Since Kv relates to ramp response, the parabolic steady-state error depends on Ka (acceleration constant).

Test

Q.54 Hard Control Systems

The sensitivity function S(s) in a feedback control system is defined as:

A T(s) = C(s)/R(s)

B S(s) = 1/[1+G(s)H(s)]

C S(s) = G(s)/[1+G(s)H(s)]

D S(s) = H(s)/[1+G(s)H(s)]

Correct Answer: B. S(s) = 1/[1+G(s)H(s)]

EXPLANATION

Sensitivity S(s) = ∂Y/∂G ÷ Y/G = 1/[1+G(s)H(s)] for unity feedback systems. It measures effect of parameter variations.

Test

Q.55 Hard Control Systems

For a system with Gc(s)G(s)H(s) = 100/[s(s+5)], the phase at ω = 5 rad/s is approximately:

A -90°

B -135°

C -180°

D -225°

Correct Answer: D. -225°

EXPLANATION

At ω=5: Phase = -90° (from 1/s) - arctan(5/1) - arctan(5/5) = -90° - 78.7° - 45° ≈ -213.7° ≈ -225°

Test

Q.56 Hard Control Systems

In a root locus plot, the asymptotes for a system with 5 poles and 2 zeros meet at a point called:

A Break-in point

B Centroid

C Pole-zero cancellation point

D Breakaway point

Correct Answer: B. Centroid

EXPLANATION

Centroid (center of asymptotes) = [Σpoles - Σzeros]/[number of poles - number of zeros]. Number of asymptotes = 5-2 = 3.

Test

Q.57 Hard Control Systems

For the characteristic equation s⁴ + 8s³ + 24s² + 32s + 15 = 0, using Routh-Hurwitz criterion, the system is:

A Stable with 2 poles on RHS

B Marginally stable

C Unstable with 4 poles on RHS

D Stable with all poles on LHS

Correct Answer: D. Stable with all poles on LHS

EXPLANATION

Routh table construction shows all positive elements in first column, indicating all poles in left half plane, making the system stable.

Test

Q.58 Hard Control Systems

For improving transient response with minimal steady-state error impact, a lead compensator should be designed to add phase lead at:

A Very low frequencies (

B The gain crossover frequency region

C Very high frequencies (>10ωgc)

D Both low and high frequencies equally

Correct Answer: B. The gain crossover frequency region

EXPLANATION

Lead compensator adds phase lead at its designed center frequency ωm. For transient improvement, it should coincide with gain crossover frequency to increase phase margin

Test

Q.59 Hard Control Systems

For a system to be controllable using state feedback u = -Kx, which condition must be satisfied?

A Rank[B] = n

B Rank[A] = n

C Rank[B AB A²B ... Aⁿ⁻¹B] = n

D Rank[C] = n

Correct Answer: C. Rank[B AB A²B ... Aⁿ⁻¹B] = n

EXPLANATION

Controllability requires the controllability matrix to have full rank n. This ensures all states can be moved from origin to any desired state

Test

Q.60 Hard Control Systems

A feedback system's sensitivity function S(s) = 1/(1+L(s)) where L(s) is loop gain. For large |L(s)|, what happens to |S(s)|?

A Becomes very large

B Becomes very small

C Remains constant

D Oscillates rapidly

Correct Answer: B. Becomes very small

EXPLANATION

When |L(s)| >> 1, the sensitivity function |S(s)| ≈ 1/|L(s)| becomes very small. This shows that high loop gain reduces sensitivity to parameter variations.

Test

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