Quiz: Electrical Engineering 30 May 2020

Quiz: Electrical Engineering
Exam: NLC
Topic: Network theorems

Each question carries 1 mark.
Negative marking: 1/4 mark
Time: 10 Minute

Q1. Which of the following will not be affected due to change in R?
(a) Bandwidth
(b) Q
(c) Resonant frequency
(d) None

Q2. The resonant frequency of an RLC series circuit is 1.5 MHz with the resonating capacitor of 150 pF. The bandwidth is 10 kHz. The effective value of the resistor is
(a) 16.3 Ω
(b) 9.5 Ω
(c) 7.4 Ω
(d) 4.7 Ω

Q3. A parallel circuit is said to be in resonance when the admittance is purely
(a) capacitive
(b) inductive
(c) susceptive
(d) conductive

Q4. Consider the following statement:
If a high Q parallel resonant circuit is loaded with a resistance
The circuit impedance reduces
The resonant frequency remains the same
The bandwidth reduces
Which of the above statements is/are correct?
(a) 3 only
(b) 2 only
(c) 1 only
(d) 1,2 and 3

Q5. A parallel resonant circuit can be employed
(a) as a high impedance
(b) to reject a small band of frequencies
(c) to amplify certain frequencies
(d) both (a) and (b)

Q6. What is the locus of the tip of the voltage phasor across R in a series RLC circuit?
(a) A Parabola
(b) An ellipse
(c) A circle
(d) A rectangular hyperbola

Q7. A non-ideal voltage source Vs has an internal impedance of Zs. if a purely resistive load is to be chosen that maximizes the power transferred to the load, its value must be
(a) 0
(b) real part of Zs
(c) magnitude of Zs
(d) complex conjugate of Zs

Q8. A capacitor is charged to a voltage of 440V and has a resistance of 35 ohm. Calculate the initial value of charging current.
(a) 100 A
(b) 0
(c) infinity
(d) 200 A

Q9. The total charge entering the terminal of an element is given by;
q = (6t² – 12t) mC
(a) 36 mA
(b) 24 mA
(c) 102 mA
(d) 72 mA

Q10. A load is connected to a circuit. At the terminals to which the load is connected, R_Th = 10 Ω and V_Th = 60 V. The maximum power supplied to the load is
(a) 400 W
(b) 1600 W
(c) 700 W
(d) 900 W

Solutions
S1. Ans. (c)
Sol. Frequency won’t be affected.

S2. Ans. (d)
Sol. Q =(resonance frequency)/bandwidth
=(ωr L)/R= 1/(ωr RC)
Value of R can be computed as R = 4.7 Ω
S3. Ans. (d)
Sol.
S4. Ans. (d)
Sol. All the statements are correct.
S5. Ans. (d)
Sol. A parallel resonant circuit can be employed as both of following
as a high impedance
to reject a small band of frequencies

S6. Ans. (c)
Sol. A circle

S7. Ans. (c)
Sol. magnitude of Zs

S8. Ans. (b)
Sol. Initially, there’s 0V voltage in a capacitor. As the capacitor charges, the voltage increases. Since a voltage is proportional to current by ohm’s law, initial current is also equal to zero.

S9. Ans. (a)
Sol. Sol. Current, i=dq/dt=d/dt (q)=d/dt (6t^2-12t)=(12t-12) mA
At t = 4s, i = 12 × 4 – 12 = 48 – 12 = 36 mA

S10. Ans. (d)
Sol. Under maximum power transfer, R_L-R_Th and voltage across R_L=V_Th/2.
∴P_(max.)=(V_Th/2)²/R_Th =(60/2)²/10=900 W

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