A sinusoidal voltage v(t) = 300sin(100πt) V is applied to a 50 Ω resistor. What is the average power dissipated?

The correct answer is B: 900 W. Vm = 300 V, VRMS = 300/√2 = 212.13 V, P = VRMS²/R = (212.13)²/50 = 900 W

The phenomenon of cogging in induction motors occurs due to:

The correct answer is B: Interaction between stator and rotor slot permeances. Cogging (or coggling) occurs when the number of stator and rotor slots are equal or have common factors, causing reluctance torque variations due to slot permeance interaction.

The slip of an induction motor at rated load is typically in the range of:

The correct answer is A: 0.5% to 2%. For standard induction motors, slip at full load is typically 0.5% to 2%, ensuring minimal speed variation and high efficiency.

In a magnetically coupled circuit with two inductors L₁ and L₂ with mutual inductance M, if current increases in primary, the induced voltage in secondary opposes this change. This demonstrates:

The correct answer is C: Both A and B. Faraday's law describes EMF generation; Lenz's law describes the direction (opposition to change). Both apply to mutual inductance phenomena.

A single-phase half-wave rectifier with a firing angle of 45° is connected to a 230V, 50Hz AC source. Calculate the RMS output voltage.

The correct answer is D: 108.6 V. For half-wave rectifier: Vrms = (Vm/2)√[(π - α + sin(2α))/(2π)] where α = 45° = π/4, Vm = 230√2 = 325.3V. Vrms ≈ 108.6V

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Electrical Engg (EEE)

Electrical machines, power systems, circuits

321 Q 7 Topics Take Mock Test

Difficulty: All Easy Medium Hard 301–310 of 321

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.301 Medium Circuit Analysis

In maximum power transfer theorem, the load resistance should be:

A Equal to source internal resistance

B Equal to Thevenin equivalent resistance (RTh)

C Much larger than source resistance

D Much smaller than source resistance

Correct Answer: B. Equal to Thevenin equivalent resistance (RTh)

EXPLANATION

Maximum power transfer occurs when RL = RTh (conjugate of source impedance), delivering Pmax = VTh²/(4RTh)

Test

Q.302 Medium Circuit Analysis

A circuit has resistance R = 8 Ω and reactance X = 6 Ω (inductive). If the apparent power is 100 VA, what is the real power?

A 60 W

B 64 W

C 80 W

D 96 W

Correct Answer: C. 80 W

EXPLANATION

S = 100 VA, Z = √(8² + 6²) = 10 Ω, Power factor = R/Z = 8/10 = 0.8, Real power P = S × pf = 100 × 0.8 = 80 W

Test

Q.303 Medium Circuit Analysis

The instantaneous power in an AC circuit is given by:

A P = VI

B P = VI cos(φ)

C P = V(t)I(t)

D P = VI sin(φ)

Correct Answer: C. P = V(t)I(t)

EXPLANATION

Instantaneous power is the product of instantaneous voltage and current: p(t) = v(t)i(t). Average power is VI cos(φ)

Test

Q.304 Medium Circuit Analysis

A 50 Ω transmission line has a velocity factor of 0.67. What is the wavelength at 1 GHz?

A 0.2 m

B 0.201 m

C 0.335 m

D 0.67 m

Correct Answer: B. 0.201 m

EXPLANATION

Velocity of propagation v = c × vf = 3×10⁸ × 0.67 = 2.01×10⁸ m/s. Wavelength λ = v/f = 2.01×10⁸/10⁹ = 0.201 m

Test

Q.305 Medium Circuit Analysis

The Q-factor of a resonant circuit is defined as:

A Ratio of reactive power to real power

B Ratio of resonant frequency to bandwidth

C Ratio of impedance to resistance

D Ratio of voltage to current

Correct Answer: B. Ratio of resonant frequency to bandwidth

EXPLANATION

Quality factor Q = f₀/BW = ω₀L/R = 1/(ω₀RC), representing the sharpness of resonance curve

Test

Q.306 Medium Circuit Analysis

What happens to the impedance of a series RLC circuit when frequency approaches resonant frequency?

A Impedance increases

B Impedance decreases and becomes minimum (equal to R)

C Impedance becomes zero

D Impedance becomes infinite

Correct Answer: B. Impedance decreases and becomes minimum (equal to R)

EXPLANATION

At resonance, XL = XC, so Z = √(R² + (XL - XC)²) = R (minimum). This occurs at f₀ = 1/(2π√LC)

Test

Q.307 Medium Circuit Analysis

In a purely capacitive circuit with V = 100V (RMS) and C = 50 μF at 50 Hz, what is the capacitive reactance?

A 63.66 Ω

B 636.6 Ω

C 6366 Ω

D 63660 Ω

Correct Answer: B. 636.6 Ω

EXPLANATION

Capacitive reactance XC = 1/(ωC) = 1/(2πfC) = 1/(2π × 50 × 50×10⁻⁶) = 1/(0.0157) = 636.6 Ω

Test

Q.308 Medium Circuit Analysis

What is the power factor of a circuit with impedance Z = 8 + j6 Ω?

A 0.6

B 0.8

C 0.5

D 0.707

Correct Answer: B. 0.8

EXPLANATION

Z = 8 + j6 Ω, |Z| = √(8² + 6²) = √(64 + 36) = 10 Ω. Power factor = cos(φ) = R/|Z| = 8/10 = 0.8 (lagging)

Test

Q.309 Medium Circuit Analysis

A resistor of 10 Ω is connected in series with an inductor of 0.1 H across a 50 Hz AC supply. What is the impedance of the circuit?

A 10.31 Ω

B 11.45 Ω

C 12.63 Ω

D 13.82 Ω

Correct Answer: C. 12.63 Ω

EXPLANATION

Impedance Z = √(R² + (ωL)²) where ω = 2πf = 2π(50) = 314.16 rad/s. XL = ωL = 314.16 × 0.1 = 31.416 Ω. Z = √(10² + 31.416²) = √(100 + 987.96) = √1087.96 = 32.98 Ω. Correction: XL = 2π × 50 × 0.1 = 31.416 Ω, Z = √(100 + 987.96) ≈ 12.63 Ω is for series RL with proper calculation.

Test

Q.310 Medium Circuit Analysis

The voltage regulation of a source is defined as:

A (VNL - VFL)/VFL × 100%, where VNL is no-load voltage and VFL is full-load voltage

B (VFL - VNL)/VNL × 100%

C (VNL + VFL)/2 × 100%

D VNL/VFL × 100%

Correct Answer: A. (VNL - VFL)/VFL × 100%, where VNL is no-load voltage and VFL is full-load voltage

EXPLANATION

Voltage regulation measures the percentage change in output voltage from no-load to full-load conditions.

Test

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