১.
What type of filter allows frequencies below a cutoff frequency to pass through?
ব্যাখ্যা
A low-pass filter (LPF) attenuates frequencies above its cutoff frequency while passing lower frequencies unchanged
৪৯তম বিসিএস ⎯ তথ্য ও যোগাযোগ প্রযুক্তি (EEE) [ ৮৯২]
মোট প্রশ্ন৩০
সিলেবাস
Exam 2
Network Theorems (DC & AC): Superposition Theorem, Thevenin’s Theorem, Norton’s Theorem, Maximum Power Transfer Theorem
RC, RL and RLC Circuits: RC and RL High-Pass, Low-Pass Filters, Band-pass, Series and Parallel RLC Resonances
AC Power and Polyphase Circuits: Apparent Power, Power Factor and Complex Power, Polyphase Systems, Single-Phase Three-Wire Systems, Three-Phase Y-Y Connection, The Delta Connection, Power measurement in Three-Phase Systems
[Source: Classes 1–2 and relevant books]
৪৯তম বিসিএস ⎯ তথ্য ও যোগাযোগ প্রযুক্তি (EEE) [ ৮৯২]
৪৯তম বিসিএস ⎯ তথ্য ও যোগাযোগ প্রযুক্তি (EEE) [ ৮৯২] · তারিখ অনির্ধারিত · ৩০ প্রশ্ন
২.
In a passive RC high-pass filter, the output is taken across which component?
ব্যাখ্যা
In an RC high-pass filter, the capacitor blocks low frequencies, while higher frequencies pass through to the resistor. Thus, the output voltage is measured across the resistor.
৩.
What is the primary function of a band-stop (notch) filter?
ব্যাখ্যা
Band-stop filters attenuate a narrow frequency band while passing others.
৪.
The quality factor (Q) of a band-pass filter indicates
ব্যাখ্যা
Higher Q means a narrower bandwidth
৫.
In a series RLC circuit at resonance, the impedance is-
ব্যাখ্যা
At resonance, XL=XC, so the net reactance is zero, making impedance purely resistive (Z=R), which is the minimum possible.
৬.
At resonance in a series RLC circuit, the phase angle between voltage and current is-
ব্যাখ্যা
Since XL=XC, the circuit is purely resistive, so voltage and current are in phase.
৭.
At resonance, the voltage across the inductor (VL) and capacitor (VC) in a series RLC circuit are-
ব্যাখ্যা
VL=IXL and VC =IXC are equal in magnitude but cancel each other due to a 180° phase difference.
৮.
If the frequency increases above resonance in a series RLC circuit, the circuit becomes-
ব্যাখ্যা
At higher frequencies, XL>XC making the circuit inductive.
৯.
In a series RLC circuit, if R is increased, the Q-factor will-
ব্যাখ্যা
Q=XL/R so increasing R reduces Q.
১০.
At resonance in a parallel RLC circuit, the line current is-
ব্যাখ্যা
The reactive branch currents cancel, minimizing the total line current.
১১.
A parallel RLC circuit is often called -
ব্যাখ্যা
It stores energy alternately between L and C, resembling a tank.
১২.
The half-power frequencies are those where the power is-
ব্যাখ্যা
Half-power points occur at 1/√2 of peak current/voltage.
১৩.
Superposition in AC circuits requires analyzing the circuit separately for
ব্যাখ্যা
Both magnitude and phase
১৪.
Superposition cannot be used to calculate-
ব্যাখ্যা
Power is nonlinear (P=I2R or V2/R), so superposition doesn’t apply.
১৫.
For a purely resistive AC circuit, max power occurs when-
ব্যাখ্যা
Resistive loads simplify to matching resistances.
১৬.
For a circuit containing a dependent current source (2Iₓ) and independent voltage source (10V), superposition-
ব্যাখ্যা
Dependent sources must remain active during superposition analysis as they rely on other circuit variables.
১৭.
In a network where Isc = (2-j3)A and Voc = (10+j15)V, the Norton admittance YN is-
ব্যাখ্যা
YN = I_sc/V_oc = (2-j3)/(10+j15) = 0.15+j0.1S
১৮.
A circuit draws 10A RMS at 120V with PF=0.8PF=0.8 lagging. The real power is-
ব্যাখ্যা
P=VI×PF=120×10×0.8=960WP=VI×PF=120×10×0.8=960W.
১৯.
The power factor angle for P=3kW and S=5kVA is
ব্যাখ্যা
θ=cos−1(P/S)=cos−1(0.6)=53.13°
২০.
For a load with S=100∠45°S=100∠45° VA, the real and reactive powers are-
ব্যাখ্যা
P=Scos(45°)=70.7W, Q=Ssin(45°)=70.7VAR
২১.
A circuit has P=800W and Q=600VAR. Its power factor is-
ব্যাখ্যা
S=√(P2 +Q2 )=1000VA, PF=P∣S∣=0.8, Since Q>0Q>0, the PF is lagging (inductive load).
২২.
In the two wattmeter method, if one wattmeter reads zero, the power factor of the load is-
ব্যাখ্যা
If one wattmeter reads zero, the phase angle ϕ=60°
Power factor cosϕ=cos60°=0.5
Since the reading becomes zero due to a lagging phase angle, the power factor is 0.5 lagging.
২৩.
In the two wattmeter method, if the load is purely inductive, what will be the readings of the two wattmeters?
ব্যাখ্যা
one wattmeter reads positive and the other negative with the same magnitude.
২৪.
In a balanced 3-phase system, the two wattmeter readings are 1000 W and 500 W, respectively. What is the reactive power (Q) of the system?
ব্যাখ্যা
Q=√3(W1−W2)=500√3
২৫.
In the two wattmeter method, if the phase sequence is reversed, what happens to the readings?
ব্যাখ্যা
Swapping Vab and Vcb causes the readings to interchange
২৬.
4. Why is Wye-Wye (Y-Y) connection rarely used in high-voltage transmission?
ব্যাখ্যা
Unbalanced loads cause voltage fluctuations. Requires a tertiary winding or grounding for practical use.
২৭.
A Delta-connected load has a line current of 50 A. What is its phase current (\(I_P\)) under balanced conditions?
ব্যাখ্যা
IL=√3Ip
২৮.
A polyphase system is generated by __
ব্যাখ্যা
A generator having two or more electrical windings which are separated by equal electrical angle generates a polyphase electrical system.
২৯.
For a star connection network, consuming power of 1.8kW and power factor 0.5, supply voltage of 230 Volts. phase impedance=?
ব্যাখ্যা
Line voltage, VL = 230 V
Power Factor, cosφ = 0.5
Power consumed = P = 1800 Watts = √3 VL x IL x cosφ
line current, IL = 9 Amperes
Since it is a star connection, phase current = line current = 9 Amperes
Phase Voltage, Vph = VL/√3 = 132.8 Volts
Phase Impedance, Zph = Vph/Iph = 14.7 Ohms
৩০.
the average value of a sinusoidal voltage source over one period of time is-
ব্যাখ্যা
for sine or cosine function, over one period of time , average value is zero