DFCCIL’21 EE: Daily Practice Quiz. 18-Sep-2021

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EXAM DATES

26 SEPT TO 30 SEPT

DFCCIL’21 EE: Daily Practices Quiz

DFCCIL’21 EE: Daily Practices Quiz 18-Sep-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 08 min.

Q1. When an average reading AC voltmeter using a half-wave rectifier is used to measure an AC voltage of rms value equal to 20 V, the reading of the meter will be:
(a) 9 V
(b) 18 V
(c) 10 V
(d) 20 V

Q2. The maximum efficiency of a half-wave rectifier is:
(a) 33.33 %
(b) 50 %
(c) 40.6 %
(d) 68 %

Q3. NAND operation with A and B inputs is:

Q4. …………materials having relative permeability much greater than unity.
(a) Ferromagnetic
(b) Paramagnetic
(c) Diamagnetic
(d) None of the above

Q5. In transformers, which of the following statements is valid?
(a) In an open circuit test, copper losses are obtained while in short circuit test, core losses are obtained
(b) In an open circuit test, current is drawn at high power factor
(c) In a short circuit test, current is drawn at zero power factor
(d) In an open circuit test, current is drawn at low power factor

Q6. For a series RLC circuit, R = 20Ω, inductive reactance (XL ) = 30 Ω and capacitive reactance (XC )=30Ω. if the applied voltage is 200 V ac, then current in the circuit is:
(a) 0 A
(b) 5 A
(c) 10 A
(d) 20 A

SOLUTIONS

S1. Ans.(a)
Sol. Vrms=20 V
⇒Vm=20√2 V
For HWR, Vavg=Vm/π=(20√2)/π=9 V.

S2. Ans.(c)
Sol.
Efficiency
Half Wave 40.53 %
Full-Wave 81.06 %

S3. Ans.(a)
Sol. NAND gate;

S4. Ans.(a)
Sol. For ferromagnetic materials, relative permeability is much greater than unity.
For a paramagnetic material, its susceptibility is positive. This is because its relative permeability is slightly greater than unity. For a diamagnetic material, the relative permeability lies between 0≤μr<1 and its susceptibility lie between −1<x <0.

S5. Ans.(d)
Sol. In open circuit test, current is drawn at low power factor while in short circuit test, current is drawn at high power factor.

S6. Ans.(c)
Sol. Here |XL |=|XC |=30 Ω
i.e., case of resonance.
So, for series resonant circuit: ZT=Zmin=R
I=V/R=200/20=10 A

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