Alternating Current PYQs Set 3 (PDF)

Set 3 of 9 · Questions 61-90 of 244

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Mere Teacher · Previous Year Questions NEET Physics · Alternating Current · Set 3 (Q61-90)
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61. $In the series LCR circuit, the power dissipation is through$ (1) $R$ (2) $L$ (3) $C$ (4) $both L and C$ 62. $A 0.07 H inductor and a 12 Ω resistor are connected in series to a 220V, 50Hz ac source. The approximate current in the circuit and the phase angle between current and source voltage are respectively. [Take π as \frac{22}{7}]$ (1) $8.8A and tan^{- 1} (\frac{11}{6})$ (2) $88A and tan^{- 1} (\frac{11}{6})$ (3) $0.88A and tan^{- 1} (\frac{11}{6})$ (4) $8.8A and tan^{- 1} (\frac{6}{11})$ 63. $A sinusoidal earner voltage is amplitude modulated. The resultant amplitude modulated wave has maximum and minimum amplitude of 120 V and 80 V respectively. The amplitude of each sideband is:$ (1) $15V$ (2) $10 V$ (3) $20 V$ (4) $5V$ 64. $An alternating current is given by i = i_{1} sin ωt + i_{2} cos ωt . The r.m.s. current is given by$ (1) $\frac{i _{1}^{2} + i _{2}^{2}}{2}$ (2) $\frac{i _{1} + i _{2}}{2}$ (3) $\frac{i _{1}^{2} - i _{2}^{2}}{2}$ (4) $\frac{i _{1} - i _{2}}{2}$ 65. $A series L - C - R circuit containing 5.0 H inductor, 80 μF capacitor and 40Ω resistor is connected to 230 V variable frequency AC source. The angular frequencies of the source at which power transferred to the circuit is half the power at the resonant angular frequency are likely to be [NEET 2021]$ (1) $25 rad/s and 75 rad / s$ (2) $50 rad / s and 25 rad/s$ (3) $46 rad / s and 54 rad / s$ (4) $42 rad / s and 58 rad / s$ 66. $Given below are two statements: Statement I: Maximum power is dissipated in a circuit containing an inductor, a capacitor and a resistor connected in series with an AC source, when resonance occurs. Statement II: Maximum power is dissipated in a circuit containing pure resistor due to zero phase difference between current and voltage. In the light of the above statements, choose the correct answer from the options given below:$ (1) $Statement I is false but Statement II is true$ (2) $Both Statement I and Statement II are true$ (3) $Statement I is true but Statement II is false$ (4) $Both Statement I and Statement II are false$ 67. $In a series L - C - R circuit, the inductance L is 10 mH, capacitance C is 1 μF and resistance R is 100Ω . The frequency at which resonance occurs is [NEET 2023]$ (1) $15.9 kHz$ (2) $1.59 rad / s$ (3) $1.59 kHz$ (4) $15.9 rad / s$ 68. $An L - C circuit contains 196 pF capacitor and a 441 μH inductor. The frequency of electromagnetic radiation emitted by antenna coupled to the L- C circuit is$ (1) $7.96 \times 10^{5} Hz$ (2) $54.1 \times 10^{5} Hz$ (3) $79.6 \times 10^{5} Hz$ (4) $5.41 \times 10^{5} Hz$ 69. $Given below are two statements: Statement I: In an LCR series circuit, current is maximum at resonance. Statement II: Current in a purely resistive circuit can never be less than that in a series LCR circuit when connected to same voltage source. In the light of the above statements, choose the correct from the options given below:$ (1) $Statement I is false but Statement II is true$ (2) $Statement I is true but Statement II is false$ (3) $Both Statement I and Statement II are true$ (4) $Both Statement I and Statement II are false$ 70. $The power factor of an R - L circuit is \frac{1}{2} . If the frequency of AC is doubled power factor will now be$ (1) $\frac{1}{3}$ (2) $\frac{1}{5}$ (3) $\frac{1}{7}$ (4) $\frac{1}{11}$ 71. $The peak voltage of the AC source is equal to [NEET 2022]$ (1) $the rms value of the AC source$ (2) $2 times the rms value of the AC source$ (3) $1/ 2 times the rms value of the AC source$ (4) $the value of voltage supplied to the circuit$ 72. $In an a.c circuit, the instantaneous e.m.f and current are given by e = 100 sin 30 t i = 20 sin (30 t - \frac{π}{4}) In one cycle of a.c the average power consumed by the circuit and the wattless current are, respectively:$ (1) $\frac{50}{2}, 0$ (2) $50,0$ (3) $50,10$ (4) $\frac{1000}{2}, 10$ 73. $LCR circuit, the resonance frequency of circuit increases two times of the initial circuit by changing C and C^{’} and R from 100Ω to 400Ω, while the inductance was kept the same. The ratio C / C^{’}, is$ (1) $2$ (2) $8$ (3) $16$ (4) $4$ 74. $A transformer has an efficiency of 80 % and works at 10 V and 4 kW . If the secondary voltage is 240 V, then the current in the secondary coil is :$ (1) $1.59 A$ (2) $13.33 A$ (3) $1.33 A$ (4) $15.1 A$ 75. $The Q-value of a series LCR circuit with L = 2 H, C = 32 μF, R = 20Ω is$ (1) $12.5$ (2) $25.0$ (3) $50.0$ (4) $125.0$ 76. $What will be the phase difference between virtual voltage and virtual current when current in the circuit is wattless?$ (1) $60^{\circ}$ (2) $45^{\circ}$ (3) $90^{\circ}$ (4) $180^{\circ}$ 77. $An ac current is represented as i = 52 + 10 co s (650 πt + \frac{π}{6}) Amp The r.m.s value of the current is$ (1) $10 Amp$ (2) $52 Amp$ (3) $100 Amp$ (4) $50 Amp$ 78. $In LCR series circuit, an alternating e.m.f. e and current i are given by the equations c = 100 sin (100 t) volt, i = 100 sin (100 t + \frac{π}{3}) mA . The average power dissipated in the circuit will be$ (1) $100 W$ (2) $10 W$ (3) $5 W$ (4) $2.5 W$ 79. $An inductor is connected to an ac source of frequency 50 Hz . The frequency of the instantaneous power developed in the circuit is$ (1) $25 Hz$ (2) $50 Hz$ (3) $100 Hz$ (4) $200 Hz$ 80. $Which of the following combinations should be selected for better tuning of an L-C-R circuit used for communication?$ (1) $R = 25 Ω, L = 1.5 H, C = 45 µF$ (2) $R = 20 Ω, L = 1.5 H, C = 35 µF$ (3) $R = 25 Ω, L = 2.5 H, C = 45 µF$ (4) $R = 15 Ω, L = 3.5 H, C = 30 µF$ 81. $Out of the following graphs, which graph shows the correct relation (graphical representation) for LC parallel resonant circuit?$ (1) (2) (3) (4) 82. $A series L - C - R circuit with inductance 10 H, capacitance 10 μF, resistance 50Ω is connected to an AC source of voltage, V = 200 sin (100 t) volt. If the resonant frequency of the L - C - R circuit is v_{0} and the frequency of the AC source is v, then [NEET 2022]$ (1) $v_{0} = v = \frac{50}{π} Hz$ (2) $v_{0} = \frac{50}{π} Hz, v = 50 Hz$ (3) $v = 100 Hz; v_{0} = \frac{100}{π} Hz$ (4) $v_{0} = v = 50 Hz$ 83. $An AC generator 10 V (rms) at 300 rad / s is connected in series with a 50Ω resistor, a 400 mH inductor and a 200 μF capacitor. The rms voltage across the inductor is$ (1) $2.5 V$ (2) $3.4 V$ (3) $6.7 V$ (4) $10.8 V$ 84. $In a series LCR circuit R = 300Ω, L = 0.9 H, C = 2.0 μF and ω = 1000 rad / sec, then impedance of the circuit is$ (1) $500Ω$ (2) $1300Ω$ (3) $400Ω$ (4) $900Ω$ 85. $An alternating current is given by the equation i = i_{1} sinωt + i_{2} coscot. The rms current will be:$ (1) $\frac{1}{2} (i_{1}^{2} + i_{2}^{2})^{\frac{1}{2}}$ (2) $\frac{1}{2} (i_{1}^{2} + i_{2}^{2})^{\frac{1}{2}}$ (3) $\frac{1}{2} (i_{1} + i_{2})^{2}$ (4) $\frac{1}{2} (i_{1} + i_{2})$ 86. $In an electrical circuit R, L, C and an a.c. voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage the current in the circuit is π/3. If instead, C is removed from the circuit, the phase difference is again π/3. The power factor of the circuit is:$ (1) $1/2$ (2) $1/ 2$ (3) $1$ (4) $3 /2$ 87. $An inductance of (200/ π) mH, a capacitance of (10^{- 3} / π) F and a resistance of 10Ω are connected in series with an a.c. source 220 V, 50 Hz . The phase angle of the circuit is$ (1) $π /6$ (2) $π /4$ (3) $π /2$ (4) $π /3$ 88. $A series L - C - R circuit is connected to an AC voltage source. When L is removed from the circuit, the phase difference between current and voltage is π /3 . If instead C is removed from the circuit, the phase difference is again π /3 between current and voltage. The power factor of the circuit is [NEET 2020]$ (1) $0.5$ (2) $1.0$ (3) $-1.0$ (4) $zero$ 89. $Capacitive reactance of a capacitor in an AC circuit is 3 kΩ . If this capacitor is connected to a new AC source of double frequency, the capacitive reactance will become$ (1) $1.5 kΩ$ (2) $3 kΩ$ (3) $6 kΩ$ (4) $5.2 kΩ$ 90. $The output of a step down transformer is measured to be 48 V when connected to a 12 W bulb. The value of peak current is$ (1) $2 A$ (2) $\frac{1}{2 2} A$ (3) $\frac{1}{4} A$ (4) $\frac{1}{2} A$