JEE Questions for Physics Alternating Current Quiz 9 - MCQExams.com


Physics-Alternating Current-62087.png
  • 11.4 Ω, 17.5 A
  • 30.7 Ω, 6.5 A
  • 40.4 Ω, 5 A
  • 50Ω, 4 A
In a series LCR circuit, operated with an ac of angularfrequency ω, the total impedance is

  • Physics-Alternating Current-62089.png
  • 2)
    Physics-Alternating Current-62090.png

  • Physics-Alternating Current-62091.png

  • Physics-Alternating Current-62092.png

Physics-Alternating Current-62093.png

  • Physics-Alternating Current-62094.png
  • 2)
    Physics-Alternating Current-62095.png

  • Physics-Alternating Current-62096.png
  • 1000 Hz
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-62098.png
  • 1.0 A

  • Physics-Alternating Current-62099.png
  • 0.8 A
In an ac circuit, a resistance of R ohm 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-62101.png
  • 2)
    Physics-Alternating Current-62102.png
  • R
  • Cannot be found with the given data
A coil of inductance L has an inductive reactance of XLin an ac circuit in which the effective current is I. The coil is made from a super–conducting material and has no resistance. The rate at which power is dissipated inthe coil is
  • 0
  • IXL
  • I2XL

  • Physics-Alternating Current-62104.png
When 100 volt dc is applied across a coil, a current of 1 amp flows through it. When 100 volt ac at 50 cycle s–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 inductor of a choke coil is 0.1 H and resistance is 12 Ω. 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
If an 8 Ω resistance and 6 Ω reactance are present in an ac series circuit, then the impedance of the circuit will be
  • 20 ohm
  • 5 ohm
  • 10 ohm

  • Physics-Alternating Current-62108.png
A 12 ohm resistor and a 0.21 henry inductor are connected in series to an ac source operating at 20 volts, 50 cycle/second. The phase angle between the current and the source voltage is
  • 30°
  • 40°
  • 80°
  • 90°
A 220 V, 50 Hz ac source is connected to an inductance of 0.2 H and a resistance of 20 ohm in series. What is the current in the circuit?
  • 10 A
  • 5 A
  • 33.3 A
  • 3.33 A
The quality factor of LCR circuit having resistance (R) and inductance (L) at resonance frequency (ω) is given by

  • Physics-Alternating Current-62114.png
  • 2)
    Physics-Alternating Current-62115.png

  • Physics-Alternating Current-62116.png

  • Physics-Alternating Current-62117.png
In an ac circuit the reactance of a coil is √3 times its resistance, the phase difference between the voltage across the coil to the current through the coil will be
  • π /3
  • π /2
  • π /4
  • π /6
The capacity of a pure capacitor is 1 farad. In dc circuits,its effective resistance will be
  • Zero
  • Infinite
  • 1 ohm
  • 1/2 Ω
In an ac circuit, the current lags behind the voltage by π /3. The components in the circuit are
  • R and L
  • R and C
  • L and C
  • Only R
The reactance of a coil when used in the domestic ac power supply (220 volts, 50 cycles per second) is 50 ohms. The inductance of the coil is nearly
  • 2.2 henry
  • 0.22 henry
  • 1.6 henry
  • 0.16 henry
For high frequency, a capacitor offers
  • More reactance
  • Less reactance
  • Zero reactance
  • Infinite reactance
The coil of choke in a circuit
  • Increases the current
  • Decreases the current
  • Does not change the current
  • Has high resistance to dc circuit
In a circuit, the current lags behind the voltage by a phase difference of is π /2. The circuit contains which ofthe following
  • Only R
  • Only L
  • Only C
  • R and C
An oscillator circuit consists of an inductance of 0.5 mH and a capacitor of 20 μF. The resonant frequency of thecircuit is nearly
  • 15.92 Hz
  • 159.2 Hz
  • 1592 Hz
  • 15910 Hz
A circuit has a resistance of 11 Ω, an inductive reactance of 25 Ω and a capacitative resistance of 18 Ω. It is connected to an ac source of 260 V and 50 Hz. The current through the circuit (in amperes) is
  • 11
  • 15
  • 18
  • 20
A 0.7 henry inductor is connected across a 120V – 60 Hz ac source. The current in the inductor will be very nearly
  • 4.55 amp
  • 0.355 amp
  • 0.455 amp
  • 3.55 amp
In ac circuit of capacitance the current from potential is
  • Forward
  • Backward
  • Both are in the same phase
  • None of the above
A coil of 200 Ω resistance and 1.0 H inductance is connected to an ac source of frequency 200 /2π Hz. Phase angle between potential and current will be
  • 30°
  • 90°
  • 45°
  • 0°
Radio frequency choke uses core of
  • Air
  • Iron
  • Air and iron
  • None of these
The current in series LCR circuit will be maximum when ω is
  • As large as possible
  • Equal o natural frequency of LCR system
  • √LC

  • Physics-Alternating Current-62126.png
In a circuit L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45°. The value of C is

  • Physics-Alternating Current-62127.png
  • 2)
    Physics-Alternating Current-62128.png

  • Physics-Alternating Current-62129.png

  • Physics-Alternating Current-62130.png
In an ac circuit the current
  • Always leads the voltage
  • Always lags behind the voltage
  • Is always in phase with the voltage
  • May lead or lag behind or be in phase with the voltage
A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillation of frequency f. If L is doubled and C is changed to 4C, the frequency will be

  • Physics-Alternating Current-62133.png
  • 2)
    Physics-Alternating Current-62134.png

  • Physics-Alternating Current-62135.png

  • Physics-Alternating Current-62136.png
A coil of inductive reactance 31 Ω has a resistance of 8 Ω. It is placed in series with a condenser of capacitative reactance 25 Ω. The combination is connected to an ac source of 110 volt. The power factorof the circuit is
  • 0.80
  • 0.33
  • 0.56
  • 0.64
In an LCR series resonant circuit which one of the following cannot be the expression for the Q–factor

  • Physics-Alternating Current-62139.png
  • 2)
    Physics-Alternating Current-62140.png

  • Physics-Alternating Current-62141.png

  • Physics-Alternating Current-62142.png
In the figure shown, three ac voltmeters are connected. At resonance,
Physics-Alternating Current-62143.png
  • V2 = 0
  • V1 = 0
  • V3 = 0
  • V1 = V2≠ 0
  • V3 = V2≠ 0
A light bulb is rated 100 W for a 220 V supply. the resistance of the bulb and the peak voltage of the sourcerespectively are
  • 242 Ω and 311 V
  • 484 Ω and 311 V
  • 484 Ω and 440 V
  • 242 Ω and 440 V
A pure inductor of 25 mH is connected to a source of 220 V. Given the frequency of the source as 50 Hz, ther.m.s. current in the circuit is
  • 7 A
  • 14 A
  • 28 A
  • 42 A
An ac voltage is applied to a resistance R and inductor L in series. If R and the inductive reactance are both equal to 3 Ω, the phase difference between the applied voltage and the current in the circuit is
  • Zero
  • π /6
  • π/4
  • π/2
A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an ac source, of 200 volt, 100 Hz, is connected across the coil, the current in thecoil will be

  • Physics-Alternating Current-62148.png
  • 2.0 A
  • 4.0 A
  • 8.0 A
An ac ammeter is used to measure current in a circuit. When a given direct current passes through the circuit, the ac ammeter reads 3 A. When another alternating current passes through the circuit, the ac ammeter reads 4 A. Then the reading of this ammeter, if dc and ac flow through the circuit simultaneously, is
  • 3 A
  • 4 A
  • 7 A
  • 5 A
A transmitter transmit at a wavelength of 300 m. A condenser of capacitance 2.4 μF is being used. The value of the inductance for the resonant circuit isapproximately
  • 10–4 H
  • 10–6 H
  • 10–8 H
  • 10–10 H
A capacitor of capacitance 1 μF is charged to a potential of 1 V. It is connected in parallel to an inductor of inductance 10–3 H. The maximum current that will flowin the circuit has the value
  • √1000 mA
  • 1 A
  • 1 mA
  • 1000 mA
In an electrical circuit R, L, C and ac voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and the current in the circuit is π /3. If instead, C is removed from the circuit, the phase difference is again π /3. Thepower factor of the circuit is
  • 1/2
  • 2)
    Physics-Alternating Current-62153.png
  • 1

  • Physics-Alternating Current-62154.png
When 100 volts dc is supplied across a solenoid, a current of 1.0 amperes 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
  • 200 Ω and 0.55 henry
  • 100 Ω and 0.86 henry
  • 200 Ω and 1.0 henry
  • 100 Ω 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 = E0 cos (ωt) is applied to the circuit. The power consumed in the circuit is

  • Physics-Alternating Current-62157.png
  • 2)
    Physics-Alternating Current-62158.png

  • Physics-Alternating Current-62159.png

  • Physics-Alternating Current-62160.png
The readings of ammeter and voltmeter in the following circuit are respectively
Physics-Alternating Current-62162.png
  • 2 A, 200 V
  • 1.5 A, 100 V
  • 1.7 A, 200 V
  • 2.2 A, 220 V
In a series circuit C = 2 μF, L =1 mH and R = 10 Ω. 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 co is applied across an inductance. The instantaneous power developed in the circuit has an angular frequency
  • ω /4
  • ω /2
  • ω
  • 2ω
The voltage of an ac source varies with time according to the equation V = 100 sin 100 πt cos 100 πt, where tis in seconds and V is in volts. Then
  • The peak voltage of the source is 50 volts
  • The peak voltage of the source is 100 volts
  • The peak voltage of the source is 100/√2 volts
  • The frequency of the source is 50 Hz
The diagram shows a capacitor C and a resistor R connected in series to an ac source. V1 and V2 are voltmeters and A is an ammeter
Consider the following statements
I. Reading in A and V2 are always in phase
II. Reading in V1 is ahead in phase with reading in V2
III. Reading in A and V1 are always in phase. Which of these statements are/is correct

Physics-Alternating Current-62166.png
  • I only
  • II only
  • I and II only
  • II and III only
In the circuit shown in figure neglecting source resistance the voltmeter and ammeter reading will respectively be
Physics-Alternating Current-62168.png
  • 0 V, 3 A
  • 150V, 3 A
  • 150 V, 6 A
  • 0V, 8A
The voltage of an ac supply varies with time (t) as V = 120 sin 100 πt cos 100 πt. The maximum voltage and frequency respectively are
  • 120 volts, 100 Hz
  • 2)
    Physics-Alternating Current-62170.png
  • 60 volts, 200 Hz
  • 60 volts, 100 Hz
A telephone wire of length 200 km has a capacitance of 0.014 μF 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
0:0:1


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