Alternating Current PYQs Set 4 (PDF)

Set 4 of 10 · Questions 91-120 of 290

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Mere Teacher · Previous Year Questions JEE Main Physics · Alternating Current · Set 4 (Q91-120)
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91. $A transformer has an efficiency of 80 % and works at 10 V and 4 kW . If the secondary voltage is 240 V, then the current in the secondary coil is :$ (1) $1.59 A$ (2) $13.33 A$ (3) $1.33 A$ (4) $15.1 A$ 92. $The Q-value of a series LCR circuit with L = 2 H, C = 32 μF, R = 20Ω is$ (1) $12.5$ (2) $25.0$ (3) $50.0$ (4) $125.0$ 93. $What will be the phase difference between virtual voltage and virtual current when current in the circuit is wattless?$ (1) $60^{\circ}$ (2) $45^{\circ}$ (3) $90^{\circ}$ (4) $180^{\circ}$ 94. $An ac current is represented as i = 52 + 10 co s (650 πt + \frac{π}{6}) Amp The r.m.s value of the current is$ (1) $10 Amp$ (2) $52 Amp$ (3) $100 Amp$ (4) $50 Amp$ 95. $In LCR series circuit, an alternating e.m.f. e and current i are given by the equations c = 100 sin (100 t) volt, i = 100 sin (100 t + \frac{π}{3}) mA . The average power dissipated in the circuit will be$ (1) $100 W$ (2) $10 W$ (3) $5 W$ (4) $2.5 W$ 96. $An inductor is connected to an ac source of frequency 50 Hz . The frequency of the instantaneous power developed in the circuit is$ (1) $25 Hz$ (2) $50 Hz$ (3) $100 Hz$ (4) $200 Hz$ 97. $Which of the following combinations should be selected for better tuning of an L-C-R circuit used for communication?$ (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) $R = 15 Ω, L = 3.5 H, C = 30 µF$ 98. $Out of the following graphs, which graph shows the correct relation (graphical representation) for LC parallel resonant circuit?$ (1) (2) (3) (4) 99. $A series L - C - R circuit with inductance 10 H, capacitance 10 μF, resistance 50Ω is connected to an AC source of voltage, V = 200 sin (100 t) volt. If the resonant frequency of the L - C - R circuit is v_{0} and the frequency of the AC source is v, then [NEET 2022]$ (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) $v_{0} = v = 50 Hz$ 100. $An AC generator 10 V (rms) at 300 rad / s is connected in series with a 50Ω resistor, a 400 mH inductor and a 200 μF capacitor. The rms voltage across the inductor is$ (1) $2.5 V$ (2) $3.4 V$ (3) $6.7 V$ (4) $10.8 V$ 101. $In a series LCR circuit R = 300Ω, L = 0.9 H, C = 2.0 μF and ω = 1000 rad / sec, then impedance of the circuit is$ (1) $500Ω$ (2) $1300Ω$ (3) $400Ω$ (4) $900Ω$ 102. $An alternating current is given by the equation i = i_{1} sinωt + i_{2} coscot. The rms current will be:$ (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) $\frac{1}{2} (i_{1} + i_{2})$ 103. $In an electrical circuit R, L, C and an a.c. voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage the current in the circuit is π/3. If instead, C is removed from the circuit, the phase difference is again π/3. The power factor of the circuit is:$ (1) $1/2$ (2) $1/ 2$ (3) $1$ (4) $3 /2$ 104. $An inductance of (200/ π) mH, a capacitance of (10^{- 3} / π) F and a resistance of 10Ω are connected in series with an a.c. source 220 V, 50 Hz . The phase angle of the circuit is$ (1) $π /6$ (2) $π /4$ (3) $π /2$ (4) $π /3$ 105. $A series L - C - R circuit is connected to an AC voltage source. When L is removed from the circuit, the phase difference between current and voltage is π /3 . If instead C is removed from the circuit, the phase difference is again π /3 between current and voltage. The power factor of the circuit is [NEET 2020]$ (1) $0.5$ (2) $1.0$ (3) $-1.0$ (4) $zero$ 106. $Capacitive reactance of a capacitor in an AC circuit is 3 kΩ . If this capacitor is connected to a new AC source of double frequency, the capacitive reactance will become$ (1) $1.5 kΩ$ (2) $3 kΩ$ (3) $6 kΩ$ (4) $5.2 kΩ$ 107. $The output of a step down transformer is measured to be 48 V when connected to a 12 W bulb. The value of peak current is$ (1) $2 A$ (2) $\frac{1}{2 2} A$ (3) $\frac{1}{4} A$ (4) $\frac{1}{2} A$ 108. $The coil of a.c. generator has 100 turns, each of cross. sectional area 2 m^{2} . It is rotating at constant angular speed 30 rad / s, in a uniform magnetic field of 2 \times 10^{- 2} T . If the total resistance of the circuit is 600Ω then maximum power dissipated in the circuit is$ (1) $6 W$ (2) $9 W$ (3) $12 W$ (4) $24 W$ 109. $A resistance of 40 Ω is connected to a source of alternating current rated 220 V, 50 Hz. Find the time taken by the current to change from its maximum value to rms value:$ (1) $2.5 ms$ (2) $1.25 ms$ (3) $2.5 s$ (4) $0.25 s$ 110. $A 40 μF capacitor is connected to a 200 V, 50 Hz AC supply. The rms value of the current in the circuit is, nearly [NEET 2020]$ (1) $2.05 A$ (2) $2.5 A$ (3) $25.1 A$ (4) $1.7 A$ 111. $An electric bulb rated as 100 W - 220 V is connected to an ac source of rms voltage 220 V. The peak value of current through the bulb is:$ (1) $0.32 A$ (2) $0.64 A$ (3) $0.45 A$ (4) $2.2 A$ 112. $The energy stored in a coil of inductance L carrying a steady current i is in the form$ (1) $magnetic$ (2) $electrical$ (3) $both magnetic and electrical$ (4) $heat$ 113. $An alternating voltage E = 2002 sin (100 t) volt is connected to a 1 μF capacitor through an a.c. ammeter. The reading of the ammeter shall be$ (1) $10 mA$ (2) $40 mA$ (3) $20 mA$ (4) $80 mA$ 114. $A capacitor C is first charged fully with potential difference of V_{0} and disconnected from the battery. The charged capacitor is connected across an inductor having inductance L . In t s 25 % of the initial energy in the capacitor is transferred to the inductor. The value of t is____s.$ (1) $\frac{π LC}{3}$ (2) $\frac{π LC}{6}$ (3) $\frac{π LC}{2}$ (4) $π \frac{LC}{2}$ 115. $In a series LCR circuit R = 300Ω, L = 0.9 H, C = 2 μF, ω = 1000 rad / s . The impedance of the circuit is$ (1) $500Ω$ (2) $1300Ω$ (3) $400Ω$ (4) $900Ω$ 116. $LC oscillations are similar and analogous to the mechanical oscillations of a block attached to a spring. The electrical equivalent of the force constant of the spring is$ (1) $reciprocal of capacitive reactance$ (2) $capacitive reactance$ (3) $reciprocal of capacitance$ (4) $capacitance.$ 117. $The reactance of an inductor at 50 Hz is 10Ω . The reactance of it at 200 Hz is$ (1) $10Ω$ (2) $40Ω$ (3) $2.5Ω$ (4) $20Ω$ 118. $A power transmission line feeds input power at 2.3 kV to a step-down transformer with its primary winding having 3000 turns. The output power is delivered at 230 V by the transformer. The current in the primary of the transformer is 5 A and its efficiency is 90 % . The winding of transformer is made of copper. The output current of transformer is A.$ 119. $An inductor stores 16 J of magnetic field energy and dissipates 32 W of thermal energy due to its resistance when an a.c. current of 2 A (rms) and frequency 50 Hz flows through it. The ratio of inductive reactance to its resistance is____(π = 3.14)$ 120. $An LCR series circuit of capacitance 62.5 nF and resistance of 50 Ω. is connected to an A.C. source of frequency 2.0 kHz. For maximum value of amplitude of current in circuit, the value of inductance is______mH. (take π^{2} = 10)$