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question_answer1)
Alternating current cannot be measured by DC ammeter because:
A)
AC cannot pass through DC ammeter done
clear
B)
AC changes direction done
clear
C)
average value of current for complete cycle is zero done
clear
D)
DC ammeter will get damaged done
clear
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question_answer2)
The sum of average current values over on complete cycle is:
A)
negative done
clear
B)
positive done
clear
C)
zero done
clear
D)
Both a. and b. done
clear
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question_answer3)
Alternating voltage (V) is represented by the equation:
A)
\[V(t)={{V}_{m}}{{e}^{\omega t}}\] done
clear
B)
\[V(t)={{V}_{m}}\sin \,\omega t\] done
clear
C)
\[V(t)={{V}_{m}}\cot \,\omega t\] done
clear
D)
\[V(t)={{V}_{m}}tan\,\omega t\] where \[{{V}_{m}}\] is the peak voltage done
clear
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question_answer4)
A \[100\text{ }\Omega \]resistor is connected to a 220 V, 50 Hz AC supply. The rms value of current in the circuit is:
A)
1.56 A done
clear
B)
1.56 mA done
clear
C)
2.2 A done
clear
D)
2.2 mA done
clear
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question_answer5)
An alternating current is given by \[l={{l}_{1}}\cos \omega t+{{l}_{2}}\sin \omega t\]. The root mean square current is given by:
A)
\[\frac{\left( {{l}_{1}}+{{l}_{2}} \right)}{\sqrt{2}}\] done
clear
B)
\[\frac{{{\left( {{l}_{1}}+{{l}_{2}} \right)}^{2}}}{2}\] done
clear
C)
\[\sqrt{\frac{l_{1}^{2}+l_{2}^{2}}{2}}\] done
clear
D)
\[\frac{\sqrt{l_{1}^{2}-l_{2}^{2}}}{2}\] done
clear
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question_answer6)
The peak voltage of an AC supply is 440 V, then its rms voltage is:
A)
31.11 V done
clear
B)
311.1 V done
clear
C)
41.11 V done
clear
D)
411.1 V done
clear
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question_answer7)
The rms value of current in an AC circuit is 25 A, then peak current is:
A)
35.36 mA done
clear
B)
35.36 A done
clear
C)
3.536 A done
clear
D)
49.38 A done
clear
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question_answer8)
An alternating voltage given by \[V=140\,\,sin\,\,314t\]is connected across a pure resistor of \[50\text{ }\Omega \], the rms current through the resistor is:
A)
1.98 A done
clear
B)
5.63 A done
clear
C)
8.43 A done
clear
D)
2.39 A done
clear
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question_answer9)
If the rms current in a 50 Hz AC circuit is 5 A. the value of the current 1/300 seconds after its value becomes zero is: (NCERT EXEMPLAR)
A)
\[5\sqrt{2}\,A\] done
clear
B)
\[5\sqrt{\frac{3}{2}}\,A\] done
clear
C)
\[\frac{5}{6}A\] done
clear
D)
\[\frac{5}{\sqrt{2}}A\] done
clear
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question_answer10)
When an AC is connected to a resistor what is the phase difference between the current and voltage?
A)
\[90{}^\circ \] done
clear
B)
\[180{}^\circ \] done
clear
C)
\[0{}^\circ \] done
clear
D)
\[60{}^\circ \] done
clear
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question_answer11)
In a purely resistive AC circuit, the current:
A)
is in phase with the e.m.f. done
clear
B)
leads the e.m.f. by a difference of \[\pi \] radian phase done
clear
C)
leads the e.m.f. by a phase difference of \[\pi /2\] radians done
clear
D)
lags behind the e.m.f. by phase difference of \[\pi /4\] radians done
clear
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question_answer12)
The voltage over a cycle varies as \[V={{V}_{0}}\sin \omega t\] for \[0\le t\le \frac{\pi }{\omega }\] \[=-{{V}_{0}}\sin \omega t\] for \[\frac{\pi }{\omega }\le t\le \frac{2\pi }{\omega }\] The average value of the voltage for one cycle is:
A)
\[\frac{{{V}_{0}}}{\sqrt{2}}\] done
clear
B)
\[\frac{{{V}_{0}}}{2}\] done
clear
C)
zero done
clear
D)
\[\frac{2{{V}_{0}}}{\pi }\] done
clear
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question_answer13)
The rms value of potential difference V as shown in the figure is:
A)
\[\frac{{{V}_{0}}}{\sqrt{3}}\] done
clear
B)
\[{{V}_{0}}\] done
clear
C)
\[\frac{{{V}_{0}}}{\sqrt{2}}\] done
clear
D)
\[\frac{{{V}_{0}}}{2}\] done
clear
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question_answer14)
The relation between an AC voltage source and time in SI units is \[V=120\,\sin \,\,(100\pi t)\,\,cos\,\,(100\pi t)V\]. The value of peak voltage and frequency will be respectively:
A)
120 V and 100 Hz done
clear
B)
\[\frac{120}{\sqrt{2}}V\]and 100 Hz done
clear
C)
60 V and 200 Hz done
clear
D)
60 V and 100 Hz done
clear
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question_answer15)
A light bulb is rated at 100 W for a 220 V AC supply. The resistance of the bulb is:
A)
\[284\,\Omega \] done
clear
B)
\[384\,\Omega \] done
clear
C)
\[484\,\Omega \] done
clear
D)
\[584\,\Omega \] done
clear
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question_answer16)
An AC source is of \[\frac{200}{\sqrt{2}}V,\,50\,Hz\]. The value of voltage after \[\frac{1}{600}s\] from the start is:
A)
\[200\,V\] done
clear
B)
\[\frac{200}{\sqrt{2}}V\] done
clear
C)
\[100\,V\] done
clear
D)
\[50\,V\] done
clear
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question_answer17)
The peak value of domestic AC supply voltage is 325 V. What is the rms value?
A)
325 V done
clear
B)
230 V done
clear
C)
200 V done
clear
D)
325 V done
clear
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question_answer18)
The equation of AC is given by \[l~=100\text{ }\sin \text{ }314t.\] What is the frequency?
A)
314 Hz done
clear
B)
100 Hz done
clear
C)
50 Hz done
clear
D)
100 Hz done
clear
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question_answer19)
The line that draws power supply to your house from street has:
A)
\[220\sqrt{2}\,V\]average voltage done
clear
B)
220 V average voltage done
clear
C)
voltage and current out of phase by \[\pi /2\] done
clear
D)
voltage and current possibly differing in phase \[\phi \] such that \[|\phi |<\frac{\pi }{2}\] done
clear
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question_answer20)
When a voltage measuring device is connected to AC mains, the meter shows the steady input voltage of 220 V. This means: (NCERT EXEMPLAR)
A)
input voltage cannot be AC voltage, but a DC voltage done
clear
B)
maximum input voltage is 220 V done
clear
C)
the meter reads not V but \[<{{V}^{2}}>\] and is calibrated to read \[\sqrt{<{{V}^{2}}>}\] done
clear
D)
the pointer of the meter is stuck by some mechanical defect done
clear
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question_answer21)
An AC source of voltage \[V={{V}_{m}}\sin \,\omega t\] is connected across the resistance R as shown in figure. The phase relation between current and voltage for this circuit is:
A)
both are in phase done
clear
B)
both are out of phase by \[90{}^\circ \] done
clear
C)
both are out of phase by \[120{}^\circ \] done
clear
D)
both are out of phase by \[180{}^\circ \] done
clear
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question_answer22)
In an AC circuit, V and l are given by \[V=150\,\sin \,(150t)V\] and \[l=150\,\sin \,\left( 150\,t+\frac{\pi }{3} \right)A\]. The power dissipated in the circuit is:
A)
106 W done
clear
B)
150 W done
clear
C)
5625 W done
clear
D)
zero done
clear
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question_answer23)
The phase relationship between current and voltage in a pure resistive circuit is best represented by:
A)
B)
C)
D)
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question_answer24)
The projection of a phasor on any axis, always represents the:
A)
rms value of a quantity done
clear
B)
peak value of a quantity done
clear
C)
mean value of a quantity done
clear
D)
instantaneous value of a quantity done
clear
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question_answer25)
The time axis of an AC phasor represents:
A)
time done
clear
B)
phase angle done
clear
C)
voltage done
clear
D)
current done
clear
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question_answer26)
A phasor is a:
A)
scalar quantity done
clear
B)
vector quantity done
clear
C)
tensor quantity done
clear
D)
None of these done
clear
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question_answer27)
In the case of an inductor:
A)
voltage lags the current by \[\frac{\pi }{2}\] done
clear
B)
voltage leads the current by \[\frac{\pi }{2}\] done
clear
C)
voltage leads the current by \[\frac{\pi }{3}\] done
clear
D)
voltage leads the current by \[\frac{\pi }{4}\] done
clear
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question_answer28)
An alternating voltage \[V={{V}_{0}}\sin \,\omega t\] is applied across a circuit. As a result, the current \[l={{l}_{0}}\sin \,(\omega t-\pi /2)\] flows in it. The power consumed in the circuit per cycle is:
A)
\[0.5\,{{V}_{0}}{{l}_{0}}W\] done
clear
B)
\[0.707\,{{V}_{0}}{{l}_{0}}W\] done
clear
C)
\[1.919\,{{V}_{0}}{{l}_{0}}W\] done
clear
D)
zero done
clear
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question_answer29)
An ideal inductor is in turn put across 220V, 50 Hz and 220 V. 100 Hz supplies. The current flowing through it in the two cases will be:
A)
equal done
clear
B)
different done
clear
C)
zero done
clear
D)
infinite done
clear
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question_answer30)
An inductor of 30 mH is connected to a 220 V, 100 Hz AC source. The inductive reactance is:
A)
\[10.58\text{ }\Omega \] done
clear
B)
\[12.64\text{ }\Omega \] done
clear
C)
\[18.85\text{ }\Omega \] done
clear
D)
\[22.67\,\,\Omega \] done
clear
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question_answer31)
Which of the following graphs represents the correct variation of inductive reactance \[{{X}_{L}}\] with frequency v?
A)
B)
C)
D)
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question_answer32)
What is the resistance offered by a pure inductor for DC?
A)
Zero done
clear
B)
Infinity done
clear
C)
One done
clear
D)
Depends on the material done
clear
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question_answer33)
A 44 mH inductor is connected to 220 V, 50 Hz AC supply. The rms value of the current in the circuit is:
A)
12.8 A done
clear
B)
13.6 A done
clear
C)
15.9A done
clear
D)
19.5 A done
clear
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question_answer34)
The reactance of a coil is \[100\,\Omega \]. when used with an AC 240V - 100 Hz supply. The inductance of the coil is:
A)
0.16 H done
clear
B)
0.22 H done
clear
C)
1.6 H done
clear
D)
2.2 H done
clear
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question_answer35)
In a circuit, the current lags behind the voltage by a phase difference of \[\pi /2\]. The circuit contains:
A)
only R done
clear
B)
only C done
clear
C)
only L done
clear
D)
R and C done
clear
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question_answer36)
In a pure capacitive circuit, if the frequency of AC source is doubled, then its capacitive reactance will be:
A)
remains same done
clear
B)
doubled done
clear
C)
halved done
clear
D)
zero done
clear
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question_answer37)
Which of the following graphs represents the correct variation of capacitive reactance \[{{X}_{C}}\] with frequency v:
A)
B)
C)
D)
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question_answer38)
If a capacitor of \[8\mu F\] is connected to a 220 V, 100 Hz AC source and the current passing through it is 65 mA, then the rms voltage across it is:
A)
129.4 V done
clear
B)
12.94 V done
clear
C)
1.294 V done
clear
D)
15 V done
clear
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question_answer39)
Phase difference between voltage and current in a capacitor in an AC circuit is:
A)
\[\pi \] done
clear
B)
\[\pi /2\] done
clear
C)
0 done
clear
D)
\[\pi /3\] done
clear
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question_answer40)
In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?
A)
Only resistor done
clear
B)
Resistor and inductor done
clear
C)
Resistor and capacitor done
clear
D)
Only inductor done
clear
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question_answer41)
A \[30\text{ }\mu F\] capacitor is connected to a 150V, 60 Hz AC supply. The rms value of current in the circuit is:
A)
17 A done
clear
B)
1.7 A done
clear
C)
1.7 MA done
clear
D)
2.7 A done
clear
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question_answer42)
A \[60\,\mu F\] capacitor is connected to a 110 V (rms), 60 Hz AC supply. The rms value of current in the circuit is:
A)
1.49 A done
clear
B)
14.9 A done
clear
C)
2.49 A done
clear
D)
24.9 A done
clear
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question_answer43)
An inductor of reactance \[1\,\Omega \] and a resistor of \[2\,\Omega \] are connected in series to the terminals of a 6V (rms) AC source. The power dissipated in the circuit is:
A)
8 W done
clear
B)
12 W done
clear
C)
14.4 W done
clear
D)
18 W done
clear
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question_answer44)
In the question number 43, the net power absorbed by the circuit in one complete cycle is:
A)
5 W done
clear
B)
10 W done
clear
C)
15 W done
clear
D)
zero done
clear
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question_answer45)
In which of the following circuits the maximum power dissipation is observed?
A)
Pure capacitive circuit done
clear
B)
Pure inductive circuit done
clear
C)
Pure resistive circuit done
clear
D)
None of these done
clear
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question_answer46)
A capacitor:
A)
blocks AC but provides an easy path for DC done
clear
B)
blocks DC but provides an easy path for AC done
clear
C)
blocks both AC and DC done
clear
D)
offers easy path for AC and DC done
clear
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question_answer47)
The rectance of a capacitor of capacitance C. is X. If both the frequency and capacitance are doubled, the new reactance will be:
A)
X done
clear
B)
2 X done
clear
C)
4 X done
clear
D)
X/4 done
clear
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question_answer48)
What is the resistance offered by a capacitor for the steady current?
A)
One done
clear
B)
Zero done
clear
C)
Infinity done
clear
D)
Depends on the voltage value done
clear
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question_answer49)
When an AC is connected to a capacitor what happens?
A)
Voltage is leading the current by \[90{}^\circ \] done
clear
B)
Voltage and current are in phase with each other done
clear
C)
Voltage and current are out of phase done
clear
D)
Current leads the voltage by \[90{}^\circ \] done
clear
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question_answer50)
Which can not allow AC to pass through?
A)
resistor done
clear
B)
inductor done
clear
C)
capacitor done
clear
D)
transistor done
clear
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question_answer51)
A capacitor of capacitance C has reactance X. If capacitance and frequency become double, then the capacitive reactance will be:
A)
2 X done
clear
B)
4 X done
clear
C)
\[\frac{X}{2}\] done
clear
D)
\[\frac{X}{4}\] done
clear
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question_answer52)
When AC voltage of 220 V is applied to the capacitor C, then:
A)
the maximum voltage between plates is 220 V done
clear
B)
the current is in phase with the applied voltage done
clear
C)
the charge on the plate is not in phase with the applied voltage done
clear
D)
power delivered to the capacitor per cycle is zero done
clear
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question_answer53)
In the circuit shown in figure, what will be the reading of the voltmeter?
A)
300 V done
clear
B)
900 V done
clear
C)
200 V done
clear
D)
400 V done
clear
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question_answer54)
In the series LCR circuit shown, the impedance is:
A)
\[200\,\Omega \] done
clear
B)
\[100\,\Omega \] done
clear
C)
\[300\,\Omega \] done
clear
D)
\[500\,\Omega \] done
clear
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question_answer55)
A circuit containing a \[20\,\Omega \] resistor and \[0.1\text{ }\mu F\]capacitor in series is connected to 230V AC supply of angular frequency \[100\text{ }rad\text{ }{{s}^{-1}}\]. The impedance of the circuit is:
A)
\[{{10}^{5}}\Omega \] done
clear
B)
\[{{10}^{4}}\Omega \] done
clear
C)
\[{{10}^{6}}\Omega \] done
clear
D)
\[{{10}^{10}}\Omega \] done
clear
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question_answer56)
A \[0.2\text{ }k\,\Omega \] resistor and \[15\text{ }\mu \text{F}\] capacitor are connected in series to a 220 V, 50 Hz source. The impedance of the circuit is:
A)
\[250\,\Omega \] done
clear
B)
\[268\,\Omega \] done
clear
C)
\[29.15\,\Omega \] done
clear
D)
\[291.5\,\Omega \] done
clear
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question_answer57)
A circuit consists of a resistance of \[10\text{ }\Omega \], and a capacitance of 0.1 up. If an alternating emf of 100V, 50 Hz is applied, the current in the circuit is:
A)
3.14m A done
clear
B)
6.28 mA done
clear
C)
1.51mA done
clear
D)
7.36 mA done
clear
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question_answer58)
200 V AC source is fed to series LCR circuit having \[{{X}_{L}}=50\,\Omega ,\,{{X}_{C}}=50\,\Omega \] and \[R=25\,\Omega \]. Potential drop across the inductor is:
A)
100 V done
clear
B)
200 V done
clear
C)
400 V done
clear
D)
10 V done
clear
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question_answer59)
In series R-L-C circuit, quality factor can be improved by:
A)
decreasing L done
clear
B)
increasing C done
clear
C)
decreasing R done
clear
D)
increasing R and L done
clear
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question_answer60)
When AC source is connected across series R-L- combination, maximum power loss will occur provided:
A)
current and voltage are in phase done
clear
B)
current from source is minimum done
clear
C)
inductance is minimum done
clear
D)
capacitance is maximum done
clear
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question_answer61)
In R-L-C series AC circuit, impedance cannot be increased by:
A)
increasing frequency of source done
clear
B)
decreasing frequency of source done
clear
C)
increasing the resistance done
clear
D)
increasing the voltage of the source done
clear
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question_answer62)
A \[100\text{ }\mu \text{F}\] capacitor is in series with a \[40\,\Omega \]. resistor, connected to a 100V, 60Hz supply. The time lag between the current maximum and the voltage maximum is:
A)
15.5 ms done
clear
B)
155 ms done
clear
C)
1.55 ms done
clear
D)
1.55 s done
clear
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question_answer63)
In series LCR circuit, the phase angle between supply voltage and current is:
A)
\[\tan \,\phi =\frac{{{X}_{L}}-{{X}_{C}}}{R}\] done
clear
B)
\[\tan \,\phi =\frac{R}{{{X}_{L}}-{{X}_{C}}}\] done
clear
C)
\[\tan \,\phi =\frac{R}{{{X}_{L}}+{{X}_{C}}}\] done
clear
D)
\[\tan \,\phi =\frac{{{X}_{L}}+{{X}_{C}}}{R}\] done
clear
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question_answer64)
An LCR circuit is predominantly capacitive if:
A)
\[{{X}_{L}}>{{X}_{C}}\] done
clear
B)
\[{{X}_{L}}<{{X}_{C}}\] done
clear
C)
\[{{X}_{L}}={{X}_{C}}\] done
clear
D)
None of these done
clear
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question_answer65)
To reduce the resonant frequency in an LCR series circuit with a generator: (NCERT EXEMPLAR)
A)
the generator frequency should be reduced done
clear
B)
another capacitor should be added in parallel to the first done
clear
C)
the iron core of the inductor should be removed done
clear
D)
dielectric in the capacitor should be removed done
clear
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question_answer66)
When an AC voltage is applied to a L-C-R circuit, which of the following is true?
A)
l and V are out of phase with each other in R done
clear
B)
l and V are in phase in L with in C, they are out of phase done
clear
C)
l and V are out of phase in both, C and L done
clear
D)
l and V are out of phase in L and in phase in C done
clear
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question_answer67)
An LCR series AC circuit is at resonance with 10 V each across L, C and R. If the resistance is halved, the respective voltages across L, C and R are:
A)
10, V, 10 V and 5 V done
clear
B)
10 V, 10 V and 10 V done
clear
C)
20 V, 20 V and 5 V done
clear
D)
20 V, 20 V and 10 V done
clear
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question_answer68)
In a series LCR circuit the voltage across an inductor, capacitor and resistor are 20 V, 20 V and 40 V respectively. The phase difference between the applied voltage and the current in the circuit is:
A)
\[30{}^\circ \] done
clear
B)
\[45{}^\circ \] done
clear
C)
\[60{}^\circ \] done
clear
D)
\[0{}^\circ \] done
clear
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question_answer69)
When an AC source of voltage \[V={{V}_{0}}\sin \,100t\] is connected across a circuit, the phase difference between the voltage V and current l in the circuit is observed to be \[\pi /4\]. as shown in figure. If the circuit consists possibly only of RC or RL or LC in series, find possible values of two elements.
A)
\[R=1k\Omega ,\,C=10\,\mu F\] done
clear
B)
\[R=1k\Omega ,\,C=1\,\mu F\] done
clear
C)
\[R=1k\Omega ,\,L=1\,0\,mH\] done
clear
D)
\[R=10k\Omega ,\,L=1\,0\,mH\] done
clear
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question_answer70)
In a circuit, L, C and R are connected in series with an alternating voltage source of frequency v. The current leads the voltage by \[45{}^\circ \]. The value of C is:
A)
\[\frac{1}{\pi v(2\pi vL-R)}\] done
clear
B)
\[\frac{1}{2\pi v(2\pi vL-R)}\] done
clear
C)
\[\frac{1}{\pi v(2\pi vL+R)}\] done
clear
D)
\[\frac{1}{2\pi v(2\pi vL+R)}\] done
clear
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question_answer71)
At resonance frequency the impedance in series LCR circuit is:
A)
maximum done
clear
B)
minimum done
clear
C)
zero done
clear
D)
infinity done
clear
View Solution play_arrow
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question_answer72)
An LCR series circuit is under resonance. If \[{{l}_{m}}\] is current amplitude, \[{{V}_{m}}\] is voltage amplitude, R is the resistance, Z is the impedance, \[{{X}_{L}}\] is the inductive reactance and \[{{X}_{C}}\] is the capacitive reactance, then:
A)
\[{{l}_{m}}=\frac{Z}{{{V}_{m}}}\] done
clear
B)
\[{{l}_{m}}=\frac{{{V}_{m}}}{{{X}_{L}}}\] done
clear
C)
\[{{l}_{m}}=\frac{{{V}_{m}}}{{{X}_{C}}}\] done
clear
D)
\[{{l}_{m}}=\frac{{{V}_{m}}}{R}\] done
clear
View Solution play_arrow
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question_answer73)
At resonant frequency the current amplitude in series LCR circuit is:
A)
maximum done
clear
B)
minimum done
clear
C)
zero done
clear
D)
infinity done
clear
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question_answer74)
The resonant frequency of a series LCR circuit with \[L=2.0\,\,H,C=32\mu F\] and \[R=10\,\Omega \]is:
A)
20 Hz done
clear
B)
30 Hz done
clear
C)
40 Hz done
clear
D)
50 Hz done
clear
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question_answer75)
Which of the following combinations should be selected for better tuning of an LCR circuit used for communication? (NCERT EXEMPLAR)
A)
\[R=20\Omega ,\,\,L=1.5\,H,C=35\mu F\] done
clear
B)
\[R=25\Omega ,\,\,L=2.5\,\,H,C=45\mu F\] done
clear
C)
\[R=15\Omega ,\,\,L=3.5\,\,H,C=30\mu F\] done
clear
D)
\[R=25\Omega ,\,\,L=1.5\,\,H,C=45\mu F\] done
clear
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question_answer76)
The Q factor of a series LCR circuit with \[L=2\,H,\,C=32\,\mu F\] and \[R=10\,\Omega \] is:
A)
15 done
clear
B)
20 done
clear
C)
25 done
clear
D)
30 done
clear
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question_answer77)
In a series LCR circuit, resistance, voltage and frequency of the main supply is \[200\text{ }\Omega ,\text{ }220\text{ }V\]and 50 Hz respectively. If capacitor is taken out from the circuit, the current lags behind the voltage by \[30{}^\circ \]. If inductor is taken out from the circuit, the current leads the voltage by \[30{}^\circ \]. The power dissipated in LCR-circuit is:
A)
zero done
clear
B)
210 W done
clear
C)
242 W done
clear
D)
305 W done
clear
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question_answer78)
A series LCR circuit with \[C=10\mu F\] and \[\omega =1000\text{ }rad/s\], has maximum current flowing through it. The value of inductance will be:
A)
100 mH done
clear
B)
10 mH done
clear
C)
1 mH done
clear
D)
cannot be calculated, unless R is known done
clear
View Solution play_arrow
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question_answer79)
In a series LCR circuit at resonance, the circuit is purely:
A)
resistive done
clear
B)
inductive done
clear
C)
capacitive done
clear
D)
either capacitive or inductive done
clear
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question_answer80)
In a LCR circuit the net reactance is equal to ohmic resistance. What is the phase difference between current and voltage?
A)
\[0{}^\circ \] done
clear
B)
\[45{}^\circ \] done
clear
C)
\[90{}^\circ \] done
clear
D)
\[30{}^\circ \] done
clear
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question_answer81)
Find the impedance of a series LCR circuit if the inductive reactance, capacitive reactance and resistance are \[6\,\Omega ,\text{ }3\Omega \] and \[4\,\Omega \] respectively. Calculate the impedance of the circuit.
A)
\[5\,\Omega \] done
clear
B)
\[25\,\Omega \] done
clear
C)
\[0\,\Omega \] done
clear
D)
\[13\,\Omega \] done
clear
View Solution play_arrow
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question_answer82)
At resonance in LCR circuit what happens to the impedance?
A)
becomes zero done
clear
B)
becomes ohmic resistance done
clear
C)
becomes high done
clear
D)
becomes infinity done
clear
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question_answer83)
Figure shows a series LCR circuit connected to a variable frequency 230 V source.
The source frequency which drives the circuit in resonance is:
A)
4 Hz done
clear
B)
5 Hz done
clear
C)
6 Hz done
clear
D)
8 Hz done
clear
View Solution play_arrow
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question_answer84)
In LCR-circuit if resistance increases, quality factor:
A)
increases finitely done
clear
B)
decreases finitely done
clear
C)
remains constant done
clear
D)
None of these done
clear
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question_answer85)
In a series LCR circuit having \[L=30\text{ }mH,\text{ }R=8\,\Omega .\] and the resonant frequency is 50 Hz. The quality factor of the circuit is:
A)
0.118 done
clear
B)
11.8 done
clear
C)
118 done
clear
D)
1.18 done
clear
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question_answer86)
A series resonant LCR circuit has a quality factor (Q-factor) \[=0.4.\text{ }I\text{f }R=2\text{ k}\,\Omega ,\text{ }C=0.1\,\mu F\], then the value of inductance is:
A)
0.1 H done
clear
B)
0.064 H done
clear
C)
2 H done
clear
D)
5 H done
clear
View Solution play_arrow
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question_answer87)
In a series LCR circuit, the plot of \[{{l}_{m}}vs\,\,\omega \]is shown in the figure. The bandwidth of this plot will be:
A)
zero done
clear
B)
\[0.1\,rad\,{{s}^{-1}}\] done
clear
C)
\[0.2\,rad\,{{s}^{-2}}\] done
clear
D)
\[0.4\,rad\,{{s}^{-1}}\] done
clear
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question_answer88)
A series LCR circuit with \[R=20\text{ }\Omega .,\text{ }L=1.5\text{ }H\]and \[C=35\mu F\,\]is connected to a variable frequency 200 V AC supply. When the frequency of the supply equals the natural frequency of the circuit, the average power transferred to the circuit in one complete cycle is:
A)
200 W done
clear
B)
2000 W done
clear
C)
100 W done
clear
D)
4000 W done
clear
View Solution play_arrow
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question_answer89)
The equations of instantaneous voltage and current are given as \[v=100\text{ }sin\text{ }314t\] and \[i=100\,\sin \,(314t+60{}^\circ )\] What is the power factor of the circuit?
A)
5000 W done
clear
B)
10000 W done
clear
C)
0 W done
clear
D)
2500 W done
clear
View Solution play_arrow
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question_answer90)
A series LCR circuit with \[R=22\,\Omega ,L=1.5\,H\]and \[C=40\mu F\] is connected to a variable frequency 220 V AC supply. When the frequency of the supply equals the natural frequency of the circuit, what is the average power transferred to the circuit in one complete cycle?
A)
2000 W done
clear
B)
2200 W done
clear
C)
2400 W done
clear
D)
2500 W done
clear
View Solution play_arrow
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question_answer91)
An alternating supply of 220 V is applied across a circuit with resistance \[22\text{ }\Omega \] and impedance \[\text{44 }\Omega \]. The power dissipated in the circuit is:
A)
1100 W done
clear
B)
550W done
clear
C)
2200 W done
clear
D)
(2200/3) W done
clear
View Solution play_arrow
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question_answer92)
An alternating current generator has an internal resistance \[{{R}_{g}}\] and an internal reactance \[{{X}_{g}}\]. It is used to supply power to a passive Load consisting of a resistance \[{{R}_{g}}\] and a reactance \[{{X}_{L}}\]. For maximum power to be delivered from the generator to the load, the value of \[{{X}_{L}}\] is equal to: (NCERT EXEMPLAR)
A)
zero done
clear
B)
\[{{X}_{g}}\] done
clear
C)
\[-{{X}_{g}}\] done
clear
D)
\[{{R}_{g}}\] done
clear
View Solution play_arrow
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question_answer93)
For an LCR circuit, the power transferred from the driving source to the driven oscillator is \[P={{l}^{2}}Z\,\cos \,\phi \]. Then:
A)
the power factor \[\cos \,\phi \ge 0,\,P\ge 0\] done
clear
B)
the driving force can give no energy to the oscillator (P = 0) in some cases done
clear
C)
the driving force cannot siphon out(P < 0)the energy out of oscillator done
clear
D)
All of the above done
clear
View Solution play_arrow
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question_answer94)
A voltage of peak value 283 V and varying frequency is applied to series LCR combination in which \[R=3\,\,\Omega ,\,\,L=25\,mH\] and\[C=400\mu F\]. Then the frequency (in Hz) of the source at which maximum power is dissipated in the above is:
A)
51.5 done
clear
B)
50.7 done
clear
C)
51.1 done
clear
D)
50.3 done
clear
View Solution play_arrow
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question_answer95)
The natural frequency \[({{\omega }_{0}})\] of oscillations in LC circuit is given by:
A)
\[\frac{1}{2\pi }\frac{1}{\sqrt{LC}}\] done
clear
B)
\[\frac{1}{\pi }\frac{1}{\sqrt{2LC}}\] done
clear
C)
\[\frac{1}{\sqrt{LC}}\] done
clear
D)
\[\sqrt{LC}\] done
clear
View Solution play_arrow
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question_answer96)
What is the analogy of force constant in electrical system?
A)
capacitance done
clear
B)
reciprocal of capacitance done
clear
C)
inductance done
clear
D)
reciprocal of inductance done
clear
View Solution play_arrow
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question_answer97)
A charged \[30\,\mu F\] capacitor is connected to a 27 mH inductor. The angular frequency of free oscillations of the circuit is:
A)
\[1.1\times {{10}^{3}}rad\text{ }{{s}^{-1}}\] done
clear
B)
\[2.1\times {{10}^{3}}\text{ }rad\text{ }{{s}^{-1}}\] done
clear
C)
\[3.1\times {{10}^{3}}rad\text{ }{{s}^{-1}}\] done
clear
D)
\[4.1\times {{10}^{3}}rad\text{ }{{s}^{-1}}\] done
clear
View Solution play_arrow
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question_answer98)
An LC circuit contains a 20 mH inductor and a \[50\text{ }\mu F\] capacitor with an initial charge of 10 mC. The resistance of the circuit is negligible. Let the instant at which the circuit which is closed be \[t=0\]. At what time the energy stored is completely magnetic?
A)
1 = 0 done
clear
B)
t = 1.57 ms done
clear
C)
t = 3.14 ms done
clear
D)
t = 6.28 ms done
clear
View Solution play_arrow
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question_answer99)
An LC circuit contains a 20 mH inductor and a \[25\text{ }\mu \text{F}\] capacitor with an initial charge of 5 mC. The total energy stored in the circuit initially is:
A)
5 J done
clear
B)
0.5 J done
clear
C)
50 J done
clear
D)
500 J done
clear
View Solution play_arrow
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question_answer100)
An LC-circuit contains 10 mH inductor and 25 mF capacitor with given initial charge. The resistance of the circuit is negligible. The energy stored in circuit is completely magnetic at time (in millisecond) the time is measured from the instant when the circuit is closed:
A)
\[0,\frac{\pi }{2},\frac{2\pi }{2},...etc\] done
clear
B)
\[\frac{\pi }{3},\frac{2\pi }{3},\frac{5\pi }{3},...etc.\] done
clear
C)
\[\frac{\pi }{4},\frac{3\pi }{4},\frac{5\pi }{5},...etc\] done
clear
D)
\[0,\frac{\pi }{8},\frac{\pi }{4},...etc.\] done
clear
View Solution play_arrow
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question_answer101)
What is the mechanical equivalent of spring constant k in LC oscillating circuit?
A)
\[\frac{1}{L}\] done
clear
B)
\[\frac{1}{C}\] done
clear
C)
\[\frac{L}{C}\] done
clear
D)
\[\frac{1}{LC}\] done
clear
View Solution play_arrow
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question_answer102)
In an ideal LC-circuit, the capacitor is charged by connecting it to a DC source, which is then disconnected. The current in the circuit:
A)
becomes zero instantaneously done
clear
B)
grows monotonically done
clear
C)
decays monotonically done
clear
D)
oscillates instantaneously done
clear
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question_answer103)
A transformer works on the principle of:
A)
self induction done
clear
B)
electrical inertia done
clear
C)
mutual induction done
clear
D)
magnetic effect of the electrical current done
clear
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question_answer104)
Transformer is used to:
A)
convert AC to DC voltage done
clear
B)
convert DC to AC voltage done
clear
C)
obtain desired DC power done
clear
D)
obtain desired AC voltage and current done
clear
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question_answer105)
For an ideal step-down transformer, the quantity which is constant for both the coils is:
A)
current in the coils done
clear
B)
voltage across the coils done
clear
C)
resistance of coils done
clear
D)
power in the coils done
clear
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question_answer106)
High voltage transmission line is preferred, as:
A)
its appliances are less costly done
clear
B)
thin power cables are required done
clear
C)
idle current very low done
clear
D)
(d) power loss is very less done
clear
View Solution play_arrow
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question_answer107)
In a transformer, the no. of turns of primary and secondary coils are 500 and 400 respectively. If 220 V is supplied to the primary coil, then ratio of currents in primary and secondary coils is:
A)
4:5 done
clear
B)
5:4 done
clear
C)
5:9 done
clear
D)
9:5 done
clear
View Solution play_arrow
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question_answer108)
Quantity that remains unchanged in a transformer is:
A)
voltage done
clear
B)
current done
clear
C)
frequency done
clear
D)
None of these done
clear
View Solution play_arrow
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question_answer109)
The core of a transformer is Laminated to reduce:
A)
flux leakage done
clear
B)
hysteresis done
clear
C)
copper loss done
clear
D)
eddy current done
clear
View Solution play_arrow
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question_answer110)
The loss of energy in the form of heat in the iron core of a transformer is:
A)
iron loss done
clear
B)
copper loss done
clear
C)
mechanical loss done
clear
D)
None of these done
clear
View Solution play_arrow
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question_answer111)
The output of a step down transformer is measured to be 24 V when connected to a 12W light bulb. The value of the peak current is: (NCERT EXEMPLAR)
A)
\[\frac{1}{\sqrt{2}}A\] done
clear
B)
\[\sqrt{2}\,A\] done
clear
C)
\[2\,A\] done
clear
D)
\[2\,\sqrt{2}\,A\] done
clear
View Solution play_arrow
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question_answer112)
In a transformer the transformation ratio is 0.3. If 220 VAC is fed to the primary, then the voltage across the secondary is:
A)
44 V done
clear
B)
55 V done
clear
C)
60 V done
clear
D)
66 V done
clear
View Solution play_arrow
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question_answer113)
The ratio of number of turns of primary coil to secondary coil in a transformer is 2 : 3. If a cell of 6 V is connected across the primary coil. then voltage across the secondary coil will be:
A)
3 V done
clear
B)
6 V done
clear
C)
9 V done
clear
D)
12 V done
clear
View Solution play_arrow
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question_answer114)
A transformer is used to light 140 W, 24 V lamp from a 240V AC mains. If the main current is 0.7 A, the efficiency of the transformer is:
A)
63.8% done
clear
B)
74% done
clear
C)
83.3% done
clear
D)
48% done
clear
View Solution play_arrow
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question_answer115)
In a step up transformer the turn ratio is 1:2. A Leclanche cell (emf = 1.5 V) is connected across the primary. The voltage across the secondary is:
A)
3 V done
clear
B)
1.5 V done
clear
C)
0.75 V done
clear
D)
zero done
clear
View Solution play_arrow
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question_answer116)
A transformer has primary and secondary winding as 2000 and 200 respectively. It is connected to a Lechlanche cell of 1.5V. What is the output voltage of the transformer?
A)
0.15 V done
clear
B)
1.5 V done
clear
C)
0.1 V done
clear
D)
0 V done
clear
View Solution play_arrow
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question_answer117)
A transformer has 100 turns in the primary coil and carries 8 A current. If input power is 1 kW, the number of turns in secondary coil to have 500 V output will be:
A)
100 done
clear
B)
200 done
clear
C)
400 done
clear
D)
300 done
clear
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question_answer118)
A 60 W load is connected to the secondary of an ideal transformer whose primary draws line voltage. If a current of 0.54 A flows in the load, the current in the primary coil is:
A)
0.27 mA done
clear
B)
2.7 A done
clear
C)
0.27 A done
clear
D)
10 A done
clear
View Solution play_arrow
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question_answer119)
The turns ratio of a transformer is given as 2 : 3. If the current through the primary coil is 3 A, thus calculate the current through the resistance.
A)
1 A done
clear
B)
4.5 A done
clear
C)
2 A done
clear
D)
1.5 A done
clear
View Solution play_arrow
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question_answer120)
When power is drawn from the secondary coil of the transformer, the dynamic resistance:
A)
increases done
clear
B)
decreases done
clear
C)
remains unchanged done
clear
D)
changes erratically done
clear
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question_answer121)
A step down transformer converts transmission line voltage from 11000V to 220V. The primary of the transformer has 6000 turns and efficiency of the transformer is 60%. If the output power is 9 kW, then the input power will be:
A)
11 kW done
clear
B)
12 kW done
clear
C)
14 kW done
clear
D)
15 kW done
clear
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question_answer122)
In the question number 121, the number of turns in the secondary is:
A)
20 done
clear
B)
80 done
clear
C)
120 done
clear
D)
160 done
clear
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question_answer123)
A power transmission line feeds input power at 2400V to a step down transformer with its primary windings having 4000 turns. What should be the number of turns in the secondary windings in order to get output power at 240 V?
A)
400 done
clear
B)
420 done
clear
C)
424 done
clear
D)
436 done
clear
View Solution play_arrow
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question_answer124)
The current drawn by the primary of a transformer, which step down 200 V to 20 V to operate a device of resistance \[20\,\Omega \] is (Assume the efficiency of the transformer to be 80%):
A)
0.125 A done
clear
B)
0.225 A done
clear
C)
0.325 A done
clear
D)
0.425 A done
clear
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question_answer125)
The primary and secondary coils of a transformer have 50 and 1500 turns respectively. The magnetic flux linked with the primary coil is given by \[\phi ={{\phi }_{0}}+4t\], where \[{{\phi }_{0}}\] is a constant. The output voltage across the secondary coil is:
A)
30 V done
clear
B)
90 V done
clear
C)
120 V done
clear
D)
220 V done
clear
View Solution play_arrow