Sinusoidal Steady State Analysis MCQ Quiz - Objective Question with Answer for Sinusoidal Steady State Analysis - Download Free PDF
Last updated on May 14, 2025
Latest Sinusoidal Steady State Analysis MCQ Objective Questions
Sinusoidal Steady State Analysis Question 1:
Current I(s) in RL circuit is given as \(\rm I(s)=\frac{1.5}{s+4}\) Obtain i(t) for t > 0
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 1 Detailed Solution
Concept
The inverse Laplace Transform of
\({k\over s+a}=ke^{-at}\)
where, k = Constant
Calculation
Given, \(\rm I(s)=\frac{1.5}{s+4}\)
On comparison, k = 1.5 and a = 4
\({1.5\over s+4}=1.5e^{-4t}\)
Sinusoidal Steady State Analysis Question 2:
If the peak voltage of a full-wave rectifier is 20 V, what is the average output voltage?
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 2 Detailed Solution
Concept
The average and RMS value of the full and half-wave rectifier are given by:
Full wave rectifier:
\(V_{o(avg)}={2V_m\over \pi}\)
\(V_{o(rms)}={V_m\over \sqrt{2}}\)
Half-wave rectifier:
\(V_{o(avg)}={V_m\over \pi}\)
\(V_{o(rms)}={V_m\over 2}\)
Calculation
Given, Vm = 20V
The average output voltage is given by:
\(V_{o(avg)}={2\times 20\over \pi}\)
\(V_{o(avg)}=\frac{40}{\pi}V\)
Sinusoidal Steady State Analysis Question 3:
What will be the current relationship in time domain for a capacitive circuit?
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 3 Detailed Solution
Concept
The current through a capacitor is given by:
\(I_C=C{dV_C\over dt}\)
where, \({dV_C\over dt}=\) Rate of change of capacitor voltage
The voltage across a capacitor is given by:
\(V_c(t)={1\over C } \int I_c(t) dt\)
Sinusoidal Steady State Analysis Question 4:
What will be the voltage relationship of frequency domain relation for inductor having time domain v(t) = Ldi/dt?
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 4 Detailed Solution
Concept
When an inductor is represented in the frequency domain, it is represented as sL and the initial current across the inductor is also considered.
After source transformation:
V(s) = sL × I(s) − Li(0)
Sinusoidal Steady State Analysis Question 5:
If the power factor of a three-phase system is 0.8, and the apparent power is 10 kVA, then what is the active power?
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 5 Detailed Solution
Power Triangle
In the given figure, the given terms represent the type of power:
P = Active Power
Q = Reactive Power
S = Apparent Power
The power factor is given by:
\(cosϕ={P\over S}\)
Calculation
Given, cos ϕ = 0.8
S = 10 kVA
The active power is given by:
\(0.8={P\over 10}\)
P = 8 kW
Top Sinusoidal Steady State Analysis MCQ Objective Questions
Two circuits having the same magnitudes of impedances are joined in parallel. The power factor of one circuit is 0.8 and of other is 0.6. The power factor of the combination is -
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 6 Detailed Solution
Download Solution PDFCalculation,
Given,
cos ϕ1 = 0.8
∴ sin ϕ1 = 0.6
cos ϕ2 = 0.6
∴ sin ϕ2 = 0.8
Asuume,
|I1| = |I2| = |I|
In complex form the phasor quantity is written as,
i = I(cos ϕ ± jsin ϕ)
Both current can be written as,
i1 = |I|(0.8 + j0.6)
i2 = |I|(0.6 + j0.8)
Resultant current (i) will be phasor sum of i1 and i2,
i = |I|(0.8 + j0.6) + |I|(0.6 + j0.8) = |I|(1.4 + j1.4)
Phase angle can caculated as,
\(\tan ϕ = \frac{imaginarry\ component}{real\ component }=\frac{1.4}{1.4 } = 1\)
ϕ = tan-1 (1) = 45°
Hence,
Power factor = cos 45° = 0.707
Alternate Method
When two circuits having the same magnitudes of impedances are joined in parallel. The power factor of the combination is
\(\cos ϕ = \frac{1}{{\sqrt {1 + \left( {{{\cos }^2}{ϕ _1} + {{\cos }^2}{ϕ _2}} \right)} }}\)
The power factor of the first circuit = 0.8 (cos ϕ1)
Power factor of second circuit = 0.6 (cos ϕ2)
The power factor of parallel combination,
\(\cos ϕ = \frac{1}{{\sqrt {1 + \left( {{{\cos }^2}{ϕ _1} + {{\cos }^2}{ϕ _2}} \right)} }}\)
\(= \frac{1}{{\sqrt {1 + {{\left( {0.8} \right)}^2} + {{\left( {0.6} \right)}^2}} }} = \frac{1}{{\sqrt 2 }} = 0.707\)Three currents i1, i2, and i3 meet at a node. if i1 = 10 sin (400t + 60°) A, and i2 = 10sin (400t - 60°) A then i3 =
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 7 Detailed Solution
Download Solution PDFKirchhoff’s Current Law (KCL): It states that the algebraic sum of currents entering a node or closed boundary is zero.
Mathematically, KCL implies that
\(\mathop \sum \limits_{n = 1}^N {i_n} = 0 \)
Where N is the number of branches connected to the node
And in is the nth current entering or leaving the node.
By this law current entering a node may be regarded as positive and current leaving a node may be regarded as negative or vice-versa.
Hence, the sum of currents entering a node is equal to the sum of the currents leaving the node.
Calculation:
Given that, three currents i1, i2, and i3 meet at a node,
From the above concept,
i1,+ i2, + i3 = 0
or, i3 = - (i1 + i2)
Since the current is given in phasor form, hence the addition of current i1 and i2 can be done by using the parallelogram method,
We have,
i1 = 10 sin (400t + 60°) A .... (1)
i2 = 10sin (400t - 60°) A .... (2)
The phasor diagram can be drawn as,
By using the parallelogram method,
|ir| = \(\sqrt{i_1^2+i^2_2+2i_1i_2cosθ}\) .... (3)
Where, it is the resultant current
We have, θ = (60° + 60°) = 120°
From equation (1), (2) & (3),
|ir| = \(\sqrt{10^2+10^2+200cos120 ^\circ}\)
|ir| = \(\sqrt{10^2+10^2+200\times -0.5}=10\)
Since i1 & i2 has the same phase angle as well as the magnitude,
∴ ir = 10sin 400t A
Since the sum of all current is zero, hence,
i3 = - ir = - 10sin 400t A
The impedance of a circuit is given by Z = 3 + j4. Its conductance will be:
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 8 Detailed Solution
Download Solution PDFConcept:
The impedance(Z) of a circuit can be written as:
Z = R ± jX
R = Resistance
X = Reactance
The admittance(Y) can be written as:
Y = G ± jB ---(1)
G = Conductance
B = Susceptance
\(Y = \frac{1}{Z}\)
Calculation:
Z = 3 + j4
\(Y = \frac{1}{Z} = \frac{1}{{3 + j4}} \)
\(= \frac{{\left( {3 - j4} \right)}}{{\left( {3 + j4} \right)\left( {3 - j4} \right)}} \)
\(Y= \frac{3}{{25}} - \frac{{j4}}{{25}}\)
Comparing this with Equation (1), we get:
\(G= \frac{3}{{25}}\)
Mistake Point:
The conductance will not be 1/R. For a given impedance, the conductance will be:
\(G=\frac{R}{|Z|^2}\)
R = Resistance
|Z|2 = Square of the magnitude of impedance
Select the option that will give the average value of the following waveform:
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 9 Detailed Solution
Download Solution PDFConcept:
The average value of a periodic waveform is given as
\({F_{avg}} = \frac{1}{T}\mathop \smallint \limits_0^T f\left( t \right)dt\)
It is also calculated by calculating the area of the given waveform.
\({F_{avg}} = \frac{A}{T}\)
Where A is the area
RMS value of a periodic waveform is given as
\({F_{rms}} = \sqrt {\frac{1}{T}\mathop \smallint \limits_0^T {{\left[ {f\left( t \right)} \right]}^2}dt} \)
Where T is the time-period of the given waveform.
Calculation:
Time period of the given waveform (T) = π
The area of the given waveform is,
\(A = \left( {\frac{1}{2} \times \alpha \times {F_m}} \right) + {F_m}\left( {\pi - 2\alpha } \right) + \left( {\frac{1}{2} \times \alpha \times {F_m}} \right)\)
= Fm (π – α)
Average value \( = \frac{{\pi - \alpha }}{\pi }{F_m}\)The current in a circuit follows the relation i = 200 sin ωt. If frequency is 50 Hz, how long will it take for the current to rise to 100 A?
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 10 Detailed Solution
Download Solution PDFConcept:
Equation of current is I = Im sin ωt
Im = Maximum current
ω = Angular frequency = 2πf
f = Frequency
Calculation:
Given, I = 100 A
f = 50 Hz
100 = 200 sin 2 × π × 50 × t
100 × π × t = 30° = π/6
t = 1/600 s
t = 1.666 ms
In the waveform shown, RMS value of voltage is
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 11 Detailed Solution
Download Solution PDFConcept:
RMS (Root mean square) value:
- RMS value is based on the heating effect of wave-forms.
- The value at which the heat dissipated in AC circuit is the same as the heat dissipated in DC circuit is called RMS value provided, both the AC and DC circuits have equal value of resistance and are operated at the same time.
-
RMS value 'or' the effective value of an alternating quantity is calculated as:
\({V_{rms}} = \sqrt{\frac{1}{T}\mathop \smallint \limits_0^T {v^2}\left( t \right)dt} \)
T = Time period
Note:
- Average or mean value of alternating current is that value of steady current which sends the same amount of charge through the circuit in a certain interval of time as is sent by alternating current through the same circuit in the same interval of time
- The ratio of the maximum value (peak value) to RMS value is known as the peak factor or crest factor.
- \(Peak\;factor = \frac{{maximum\;value}}{{rms\;value}}\)
- The ratio of RMS value to the average value is known as the form factor.
- \(Form\;factor = \frac{{rms\;value}}{{average\;value}}\)
Calculation:
For a rectangular wave, the RMS value is equal to the average value. RMS value is also equal to peak value.
For given waveform RMS value is 100 V.
IMPORTANT EVALUATIONS:
WAVEFORM |
MAX. VALUE |
AVERAGE VALUE |
RMS VALUE |
FORM FACTOR |
CREST FACTOR |
SINUSOIDAL WAVE |
\({A_m}\) |
\(\frac{{2{A_m}}}{\pi }\) |
\(\frac{{{A_m}}}{{\sqrt 2 }}\) |
\(\frac{{\frac{{{A_m}}}{{\sqrt 2 }}}}{{\frac{{2{A_m}}}{\pi }}} = 1.11\) |
\(\frac{{{A_m}}}{{\frac{{{A_m}}}{{\sqrt 2 }}}} = \sqrt 2 \) |
SQUARE WAVE |
\({A_m}\) |
\({A_m}\)
|
\({A_m}\)
|
\(\frac{{{A_m}}}{{{A_m}}} = 1\) |
\(\frac{{{A_m}}}{{{A_m}}} = 1\) |
TRIANGULAR WAVE |
\({A_m}\) |
\(\frac{{{A_m}}}{2}\) |
\(\frac{{{A_m}}}{{\sqrt 3 }}\) |
\(\frac{{\frac{{{A_m}}}{{\sqrt 3 }}}}{{\frac{{{A_m}}}{2}}} = \frac{2}{{\sqrt 3 }}\) |
\(\frac{{{A_m}}}{{\frac{{{A_m}}}{{\sqrt 3 }}}} = \sqrt 3 \) |
HALF-WAVE RECTIFIED WAVE
|
\({A_m}\) |
\(\frac{{{A_m}}}{\pi }\) |
\(\frac{{{A_m}}}{2}\) |
\(\frac{{\frac{{{A_m}}}{2}}}{{\frac{{{A_m}}}{\pi }}} = \frac{\pi }{2}\) |
\(2\) |
The voltage transfer function of the network shown in the figure below is
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 12 Detailed Solution
Download Solution PDFConcept:
The Laplace transform resistance, inductor, and capacitance are given by:
- Resistance: R
- Inductor: sL
- Capacitor: \({1\over sC}\)
Calculation:
The circuit diagram in the Laplace domain is given below:
Applying voltage division rule across capacitor:
\(V_{out}(s) = V_{in}\times{{1 \over s}\over {1 \over s}+2s}\)
\({V_{out}(s)\over V_{in}(s)} ={1\over{1 +2s^2}}\)Currents through ammeters A2 and A3 in the figure are 1∠10° and 1∠70°, respectively. The reading of the ammeter A1 (rounded off to 3 decimal places) is _____ A.
Answer (Detailed Solution Below) 1.700 - 1.750
Sinusoidal Steady State Analysis Question 13 Detailed Solution
Download Solution PDFConcept:
KCL in DC circuits:
According to Kirchhoff’s current law (KCL), the algebraic sum of the electric currents meeting at a common point is zero. I.e. the sum of currents entering a node is equal to the sum of currents leaving the node. It is based on the conservation of charge.
KCL in AC circuits:
Kirchhoff’s current law as applied to the ac circuit is defined as the phasor sum of currents entering the node is equal to the phasor sum of currents leaving the node.
Calculation:
By applying KCL at the node,
I1 = I2 + I3
I1 = 1∠10° + 1∠70°
= (cos 10 + j sin 10) + (cos 70 + j sin 70)
= (cos 10 + cos 70) + j(sin 10 + sin 70)
= 1.3268 + j1.1133 A
⇒ I1 = 1.732∠ 40° A
A 120 Ω resistor is in parallel with a capacitor with a capacitive reactance of 40Ω. Both components are across a 20 V AC source. What is the magnitude of the total current through the circuit?
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 14 Detailed Solution
Download Solution PDFThe correct answer is option 4):\(\sqrt {\frac{5}{{18}}} A\)
Concept:
The magnitude of the total current through the circuit
I = \(\sqrt{I_R^2+(I_L -I_C)^2} \)
where
IR is the resistive component of current
IL is the Inductive component of current
IC is the Capacitive component of current
IR = \(V\over R\)
V is the voltage
R is the resistance
IC = \(V\over X_c\)
Xc is the capacitive reactance
IL = \(V\over X_L\)
XL is the inductive reactance
Calculation:
The impedance of a network is given as
I = \(\sqrt{I_R^2+(I_L -I_C)^2} \)
IR = \(20 \over 120 \)
= \(1\over 6\)
Ic = \(20 \over 40\)
= \(1\over 2\)
I = \(\sqrt(\frac{1}{36}+\frac{1}{4})\)
= \(\sqrt {{4+36} \over 36\times 4}\)
=\( \sqrt{10 \over 36} \)
= \(\sqrt {\frac{5}{{18}}} A\)
A series Circuit Containing a circuit element has following current and applied voltage
V = 200 Sin (2000t + 50°) V
i = 4 cos (2000t + 13.2°) A
The element Comprising the circuit is
Answer (Detailed Solution Below)
Sinusoidal Steady State Analysis Question 15 Detailed Solution
Download Solution PDFGiven that,
V = 200 Sin (2000t + 50°) V
i = 4 cos (2000t + 13.2°) A
We know that,
sin (90 + ϕ) = cos ϕ
⇒ V = 200 sin (2000t + 50°) V --------- (i)
⇒ i = 4 sin (2000t + 13.2°+ 90°) A
⇒ i = 4 sin (2000t + 103.2°) A ------- (ii)
From, (i) and (ii) we can observe that,
Current 'i' is leading voltage V by 53.2°
Hence, the element is practical capacitor