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Alternating Current

116 Questions Start Allen Test
All Exams Allen
Q101 Allen 5. PYQ MCQ
An emf is generated by an ac generator having 100 turn coil, of loop area $1\mathrm{m}^2$ . The coil rotates at a speed of one revolution per second and placed in a uniform magnetic field of 0.05 T perpendicular to the axis of rotation of the coil. The maximum value of emf is :-
A.
3.14 V
B.
31.4 V
C.
62.8 V
D.
6.28 V
Q102 Allen 5. PYQ MCQ
For very high frequencies, the effective impedance of the circuit (shown in the figure) will be :-
A.
$4\Omega$
B.
$6\Omega$
C.
$1\Omega$
D.
$3\Omega$
Q103 Allen 5. PYQ MCQ
A 10 $\mu$ F capacitor is connected to a 210 V, 50 Hz source as shown in figure. The peak current in the circuit is nearly ( $\pi = 3.14$ ): 210V, 50 Hz
A.
$0.58\mathrm{A}$
B.
$0.93\mathrm{A}$
C.
$1.20\mathrm{A}$
D.
$0.35\mathrm{A}$
Q104 Allen 5. PYQ MCQ
In the circuit shown below, the inductance L is connected to an ac source. The current flowing in the circuit is $I = I_{0} \sin\omega t$ . The voltage drop ( $V_{L}$ ) across L is :
A.
$\omega \mathrm{L}I_0\sin \omega t$
B.
$\frac{\mathrm{I}_0}{\omega\mathrm{L}}\sin \omega t$
C.
$\frac{\mathrm{I}_0}{\omega\mathrm{L}}\cos \omega t$
D.
$\omega \mathrm{L}I_0\cos \omega t$
Q105 Allen 5. PYQ MCQ
A step up transformer is connected to an ac mains supply of 220 V to operate at 11000 V, 88 watt. The current in the secondary circuit, ignoring the power loss in the transformer, is:
A.
8 mA
B.
4 mA
C.
0.4 A
D.
4 A
Q106 Allen 5. PYQ MCQ
The amplitude of the charge oscillating in a circuit decreases exponentially as $Q = Q_{0}e^{-Rt/2L}$ , where $Q_{0}$ is the charge at t = 0 s. The time at which charge amplitude decreases to 0.50 $Q_{0}$ is nearly: [Given that R = 1.5Ī©, L = 12 mH, ln(2) = 0.693]
A.
19.01 ms
B.
11.09 ms
C.
19.01 s
D.
11.09 s
Q107 Allen 6. ANALYTICAL QUESTIONS MCQ
If R, C, and L be the resistance, capacitance, and inductance in the circuit in which ac of frequency f is set up, then which of the following have the dimensions of R?
(a) fC (b) fL (c) 1/fC (d) L/f
A.
only a & b
B.
only b & c
C.
only c & d
D.
all
Q108 Allen 6. ANALYTICAL QUESTIONS MCQ
In an RLC series circuit shown in figure, the readings of voltmeters $V_{1}$ and $V_{2}$ are 100 V and 120 V respectively. The source voltage is 130 V. For this situation mark out the correct statement(s).

(a) Voltage across resistor, inductor and capacitor are 50 V, 86.6 V and 206.6 V, respectively
(b) Voltage across resistor, inductor and capacitor are 10V,90 V and 30 V, respectively
(c) Power factor of the circuit is $\frac{5}{13}$ (d) The circuit is capacitive in nature
A.
a, c, d
B.
b, c, d
C.
c, d
D.
None
Q109 Allen 6. ANALYTICAL QUESTIONS Match the Columns
Match the column : In Column-I, variation of current I with t is given
in figures. In Column-II root mean square current irms, and average current are given. Match the column I with corresponding quantities given in Column II.
Column-IColumn-II
(A)
(B)
(C)
(D)
(P)$i_{rms} = \frac{i_0}{\sqrt{2}}$
(Q)Average current is $i_0$
(R)$I_{rms} = \frac{i_0}{\sqrt{3}}$
(S)None of above
A.
A ā€“ S, B ā€“ Q, C ā€“ Q, D ā€“ P
B.
A ā€“ P, B ā€“ Q, C ā€“ S, D ā€“ P
C.
A ā€“ Q, B ā€“ P, C ā€“ R, D ā€“ S
D.
A ā€“ P, B ā€“ P,Q, C ā€“ P, D ā€“ P
Q110 Allen 6. ANALYTICAL QUESTIONS Match the Columns
Match the follwoing: Column-I with Column-II
Column-IColumn-II
(A)LCR circuits
(B)Inductor
(C)More resistance
(D)Radio Tuner's characteristic curve (I ā€“ f)
(P)Resonant curve will be flattened
(Q)Sharpness indicates sensitivity
(R)Have resonant frequency $\omega = \frac{1}{\sqrt{LC}}$ with maximum current
(S)Analogous to mass
A.
A-R, B-S, C-Q, D-P
B.
A-Q, B-P, C-Q, D-R
C.
A-S, B-Q, C-R, D-P
D.
A-R, B-S, C-P, D-Q
Q111 Allen 6. ANALYTICAL QUESTIONS Match the Columns
Match the column
Column-I
Column-IColumn-II
(A)In L-R series AC circuit
(B)In R-C series AC circuit
(C)In L-C series AC circuit ($X_L > X_C$)
(D)In purely resistive AC circuit
(P)Current lags voltage by $\pi/2$
(Q)Current lags voltage by an angle less than $\pi/2$
(R)Current leads voltage by an angle less than $\pi/2$
(S)Current and voltage are in phase
A.
A-Q, B-R, C-P, D-S
B.
A-S, B-Q, C-P, D-R
C.
A-S, B-R, C-Q, D-P
D.
A-P, B-S, C-R, D-Q
Q112 Allen 6. ANALYTICAL QUESTIONS MCQ
Given below are two statements: one is
labelled as Assertion (A) and the other is
labelled as Reason (R).
Assertion (A) : Smaller the band width,
sharper the resonance and easier it is to tune an LCR circuit.
Reason (R) : Resonant frequency is arithmetic mean of half power frequencies.
In the light of the above statements, choose the most appropriate answer from the
options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q113 Allen 6. ANALYTICAL QUESTIONS MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : The impedance of series LCR circuit can be greater, equal or less than the resistance.
Reason (R) : The impedance of series LCR circuit depends over angular frequency of applied emf.
In the light of the above statements,
choose the most appropriate answer from the options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q114 Allen 6. ANALYTICAL QUESTIONS MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : In a series LCR circuit at resonance, the voltage across the capacitor or inductor may be more than the applied voltage.
Reason (R) : At resonance in a series LCR circuit, the voltages across inductor and capacitor are equal & 180Ā° out of phase.
In the light of the above statements, choose the most appropriate answer from the
options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q115 Allen 6. ANALYTICAL QUESTIONS MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Average power consumed in an ac circuit is equal to average power consumed by resistors in the circuit.
Reason (R) : Average power consumed by capacitor and inductor is zero
In the light of the above statements,
choose the most appropriate answer from the options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q116 Allen 6. ANALYTICAL QUESTIONS Match the Columns
Box may have any series combination of L, C and R. Column-I represents source current and Column-II represents possible statements.

image.png
Column-IColumn-II
(A)
(B)
(C)
(D)
(P)Box may contain LCR.
(Q)Box may contain only LR.
(R)Power factor of box is zero.
(S)Box may contain only CR.
(T)State of resonance.
A.
$\mathrm{A}\rightarrow \mathrm{P},\mathrm{B}\rightarrow \mathrm{R},\mathrm{C}\rightarrow \mathrm{PS},\mathrm{D}\rightarrow \mathrm{P}$
B.
$\mathrm{A}\rightarrow \mathrm{PT},\mathrm{B}\rightarrow \mathrm{R},\mathrm{C}\rightarrow \mathrm{PS},\mathrm{D}\rightarrow \mathrm{PQ}$
C.
$\mathrm{A}\rightarrow \mathrm{PT},\mathrm{B}\rightarrow \mathrm{PR},\mathrm{C}\rightarrow \mathrm{P},\mathrm{D}\rightarrow \mathrm{PQ}$
D.
$\mathrm{A} \rightarrow \mathrm{P}, \mathrm{B} \rightarrow \mathrm{PR}, \mathrm{C} \rightarrow \mathrm{P}, \mathrm{D} \rightarrow \mathrm{T}$