JEE Questions for Physics Alternating Current Quiz 3 - MCQExams.com

The impedance of a R-C circuit is Z1 for a frequency f and Z2for frequency 2f. Then, Z1 /Z2 is
  • Between 1 and 2
  • 2
  • Between 1/2 and 1
  • 1/2
  • 4
In a series LCR circuit, operated with an ac of angular frequency ω, the total impedance is

  • Physics-Alternating Current-61432.png
  • 2)
    Physics-Alternating Current-61433.png

  • Physics-Alternating Current-61434.png

  • Physics-Alternating Current-61435.png
In an LCR series ac circuit the voltage across L, C and R is 10 V each. If the inductor is short circuited, the voltage across the capacitor would become
  • 10 V
  • 2)
    Physics-Alternating Current-61436.png

  • Physics-Alternating Current-61437.png

  • Physics-Alternating Current-61438.png
  • 20 V
An e.m.f. E = 4 cos (1000 t) volt is applied to an LR ̶ circuit of inductance 3 mH and resistance 4 ohms. The amplitude of current in the circuit is

  • Physics-Alternating Current-61440.png
  • 1.0 A

  • Physics-Alternating Current-61441.png
  • 0.8 A
In an ac circuit, a resistance of R ohms is connected in series with an inductance L. If phase angle between voltage and current be 45°, the value of inductive reactance will be

  • Physics-Alternating Current-61443.png
  • 2)
    Physics-Alternating Current-61444.png
  • R
  • Cannot be found with the given data
The phase difference between the current and voltage of LCR circuit in series combination at resonance is
  • 0
  • π/2
  • π
  • - π
When 100 volt dc is applied across a coil, a current of 1 amp flows through it. When 100 volt ac at 50 cycles–1 is applied to the same coil, only 0.5 ampere current flows. The impedance of the coil is
  • 100 Ω
  • 200 Ω
  • 300 Ω
  • 400 Ω
The coefficient of induction of a choke coil is 0.1 H and resistance is 12Ω. If it is connected to an alternating current source of frequency 60 Hz, then power factor will be
  • 0.32
  • 0.30
  • 0.28
  • 0.24
What will be the phase difference between virtual voltage and virtual current, when the current in the circuit is wattless
  • 90°
  • 45°
  • 180°
  • 60°
The resonant frequency of a circuit is f. If the capacitance is made 4 times the initial values, then the resonant frequency will become
  • f/2
  • 2f
  • f
  • f/4
In the non-resonant circuit, what will be the nature of the circuit for frequencies higher than the resonant frequency
  • Resistive
  • Capacitive
  • Inductive
  • None of these
In a series LCR circuit, resistance R = 100 Ω and the impedance Z = 20 Ω. The phase difference between the current and the voltage is
  • 30°
  • 45°
  • 60°
  • 90°
An LC circuit contains a 20 mH inductor and a 50 μF capacitor with an initial charge of 10 mC. The resistance of the circuit is negligible. At the instant the circuit is closed be t = 0. At what time is the energy stored completely magnetic
  • t = 0
  • t = 1.54 ms
  • t = 3.14 ms
  • t = 6.28 ms
An ideal choke draws a current of 8 A when connected to an ac supply of 100 V, 50 Hz. A pure resistor draws a current of 10 A when connected to the same source. The ideal choke and the resistor are connected in series and then connected to the ac source of 150 V, 40 Hz. The current in the circuit becomes

  • Physics-Alternating Current-61454.png
  • 8 A
  • 18 A
  • 10 A
In the circuit shown below, the ac source has voltage V = 20 cos (ωt) volts with ω = 2000 rad/sec. The amplitude of the current will be nearest to
Physics-Alternating Current-61456.png
  • 2 A
  • 3.3 A

  • Physics-Alternating Current-61457.png

  • Physics-Alternating Current-61458.png

Physics-Alternating Current-61460.png
  • 30 Hz
  • 60 Hz
  • 75 Hz
  • 50 Hz
Power factor is maximum in an LCR circuit when
  • XL = XC
  • R = 0
  • XL = 0
  • XC = 0
A resistance of 40 ohm and an inductance of 95.5 millihenry are connected in series in a 50 cycles/second ac circuit. The impedance of this combination is very nearly
  • 30 ohm
  • 40 ohm
  • 50 ohm
  • 60 ohm

Physics-Alternating Current-61464.png
  • 50 μF
  • 25 μF
  • 100 μF
  • 75 μF
The power factor of an ac circuit having resistance (R) and inductance (L) connected in series and an angular velocity ω is
  • R /ωt
  • R /(R2+ ω2L2)1/2
  • ωL /R
  • R /(R2 - ω2L2)1/2
There is a 5Ω resistance in an ac circuit. Inductance of 0.1 H is connected with it in series. If equation of ac e.m.f. is 5 sin 50t, then the phase difference between current and e.m.f. is

  • Physics-Alternating Current-61467.png
  • 2)
    Physics-Alternating Current-61468.png

  • Physics-Alternating Current-61469.png
  • 0
In LCR circuit the pd between the terminals of the inductance is 60V, between the terminals of the capacitor is 30V and that between the terminals of resistance is 40V, The supply voltage will be equal to
  • 50 V
  • 70 V
  • 130 V
  • 10 V
In a LCR circuit capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the inductance should be change from L to
  • 4L
  • 2L
  • L /2
  • L /4
In an LCR series ac circuit, the voltage across each of the components, L, C and R is 50 V. The voltage across the LC combination will be
  • 50 V
  • 50√2 V
  • 100 V
  • 0 (zero)
An inductance of (200/π) mH, a capacitance of (10 ̶ 3/π)F and a resistance of 10Ω are connected inseries with an ac source 220 V, 50 Hz. The phase angleof the circuit is
  • π/6
  • π/4
  • π/2
  • π/3
An inductor L and a capacitor C are connected in the circuit as shown in the figure. The frequency of the power supply is equal to the resonant frequency of the circuit.Which ammeter will read zero ampere?
Physics-Alternating Current-61475.png
  • A1
  • A2
  • A3
  • None of these
Which of the following components of an LCR circuit, with as supply, dissipates energy
  • L
  • R
  • C
  • All of these
In a choke coil, the reactance XL and resistance R are such that
  • XL = R
  • XL>> R
  • XL << R
  • XL = oo
The phase difference between the ac and emf is π/2. Which of the following cannot be the constituent of the circuit
  • LC
  • L alone
  • C alone
  • R, L
In a series resonant LCR circuit, the voltage across R is 100 volts and R =1 kΩ with C = 2 µF. The resonant frequency ω is 200 rad/s. At resonance the voltageacross L is
  • 40 V
  • 250 V

  • Physics-Alternating Current-61477.png

  • Physics-Alternating Current-61478.png
The self inductance of the motor of an electric fan is 10 H. In order to impart maximum power of 50 Hz, it should be connected to a capacitance of
  • 1 µF
  • 2 mF
  • 4 mF
  • 8 mF
A 50 volt ac is applied across an RC (series) network. The r.m.s. voltage across the resistance is 40 volt, then the potential across the capacitance would be
  • 10 V
  • 20 V
  • 30 V
  • 40 V
A pure inductance coil of 30 mH is connected to an ac source of 220 V. The r.m.s. current in the coil is
  • 50.35 A
  • 23.4 A
  • 30.5 A
  • 12.3 A
In ac series circuit, the resistance, inductive reactance and capacitive reactance are 3Ω,10Ω and 14Ω respectively. The impedance of the circuit is
  • 5Ω
  • 4Ω
  • 7Ω
  • 10Ω
When 100 volts dc is supplied across a solenoid, a current of 1.0 ampere flows in it. When 100 volts ac is applied across the same coil, the current drops to 0.5 ampere. If the frequency of ac source is 50 Hz, then the impedance and inductance of the solenoid are
  • 200Ω and 0.55 henry
  • 100Ω and 0.86 henry
  • 200Ω and 1.0 henry
  • 100Ω and 0.93 henry
In an LR-circuit, the inductive reactance is equal to the resistance R of the circuit. An e.m.f. E = E0cos (ωt) is applied to the circuit. The power consumed in the circuit is

  • Physics-Alternating Current-61485.png
  • 2)
    Physics-Alternating Current-61486.png

  • Physics-Alternating Current-61487.png

  • Physics-Alternating Current-61488.png
One 10 V, 60 W bulb is to be connected to 100 V line. The required induction coil has self inductance of value (f = 50 Hz)
  • 0.052 H
  • 2.42 H
  • 16.2 mH
  • 1.62 mH
In a series circuit C = 2µF, L =1 mH and R=10Ω. When the current in the circuit is maximum, at that time the ratio of the energies stored in the capacitor and the inductor will be
  • 1 : 1
  • 1 : 2
  • 2 : 1
  • 1 : 5
An alternating e.m.f. of angular frequency ω is applied across an inductance. The instantaneous power developed in the circuit has an angular frequency
  • ω/4
  • ω/2
  • ω
  • 2ω
A telephone wire of length 200 km has a capacitance of 0.014µF per km. If it carries an ac of frequency 5 kHz, what should be the value of an inductor required to be connected in series so that the impedance of the circuit is minimum
  • 0.35 mH
  • 35 mH
  • 3.5 mH
  • Zero
A virtual current of 4 A and 50 Hz flows in an ac circuit containing a coil. The power consumed in the coil is 240 W. If the virtual voltage across the coil is 100 V its inductance will be

  • Physics-Alternating Current-61494.png
  • 2)
    Physics-Alternating Current-61495.png

  • Physics-Alternating Current-61496.png

  • Physics-Alternating Current-61497.png
A circuit draws 330 W from a 110 V, 60 Hz ac line. The power factor is 0.6 and the current lags the voltage. The capacitance of a series capacitor that will result in a power factor of unity is equal to
  • 31 µF
  • 54 µF
  • 151 µF
  • 201 µF
In the adjoining figure the impedance of the circuit will be
Physics-Alternating Current-61500.png
  • 120 ohm
  • 50 ohm
  • 60 ohm
  • 90 ohm
The figure shows variation of R, XL and XC with frequency f in a series L,C,R circuit. Then for what frequency point, the circuit is inductive
Physics-Alternating Current-61502.png
  • A
  • B
  • C
  • All points
When an ac source of e.m.f. e = E0 sin(100t) is connected across a circuit, the phase difference between the e.m.f. e and the current iin the circuit is observed to be π/4, as shown in the diagram. If the circuit consists possibly only of RC or LC in series, find the relationship between the two elements
Physics-Alternating Current-61504.png
  • R = 1 kΩ, C = 10µF
  • R = 1 kΩ, C = 1µF
  • R = 1 kΩ, L = 10H
  • R = 1 kΩ, L = 1H
A bulb and a capacitor are in series with an ac source. On increasing frequency how will glow of the bulb change
  • The glow decreases
  • The glow increases
  • The glow remain the same
  • The bulb quenches
What is the r.m.s. value of an alternating current which when passed through a resistor produces heat which is thrice of that produced by a direct current of 2 amperes in the same resistor
  • 6 amp
  • 2 amp
  • 3.46 amp
  • 0.66 amp

Physics-Alternating Current-61508.png
  • 0.6, 0.06 W
  • 0.06, 0.6 W
  • 0.6, 4.8 W
  • 4.8, 0.6 W
In an LCR circuit R = 100 ohm. When capacitance C is removed, the current lags behind the voltage by π/3. When inductance L is removed, the current leads the voltage by π/3. The impedance of the circuit is
  • 50 ohm
  • 100 ohm
  • 200 ohm
  • 400 ohm
A group of electric lamps having a total power rating of 1000 watt is supplied by an ac voltage E = 200 sin(310t + 60° ). Then the r.m.s. value of the circuit current is
  • 10A
  • 10√2 A
  • 20 A
  • 20√2 A
0:0:1


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