Alternating Current PYQs Set 5 (PDF)

Set 5 of 10 · Questions 121-150 of 290

In the print window choose “Save as PDF”. The file prints without a web address or date line.

Mere Teacher · Previous Year Questions JEE Main Physics · Alternating Current · Set 5 (Q121-150)
Scan or visit mereteacher.com for free PYQ practice, timed CBT tests, step-by-step solutions and BroBot AI. Answers and solutions are free with a sign-up.
121. $A resistor of resistance R and an inductor of inductive reactance R are connected in series to an ac source. A capacitor of capacitive reactance 2 R is then connected in series with L and R . The ratio of the power fators of LR and LCR circuits is$ (1) $1 : 1$ (2) $1 : 2$ (3) $1 : 3$ (4) $2 : 3$ 122. $An ideal choke draws a current of 8 A when connected to an AC supply of 100 V, 50 Hz . A pure resistor draws a current of 10 A when connected to the same source. The ideal choke and the resistor are connected in series and then connected to the AC source of 150 V, 40 Hz . The current in the circuit becomes$ (1) $\frac{15}{2} A$ (2) $8 A$ (3) $18 A$ (4) $10 A$ 123. $For a series LCR circuit with R = 100Ω, L = 0.5 mH and C = 0.1pF connected across 220V-50Hz AC supply, the phase angle between current and supplied voltage and the nature of the circuit is:$ (1) $0^{0}, resistive circuit$ (2) $\approx 9 0^{0}, predominantly inductive circuit$ (3) $0^{0}, resonance circuit$ (4) $\approx 9 0^{0}, predominantly capacitive circuit$ 124. $When a capacitor is connected to a battery$ (1) $an alternating current flow in the circuit$ (2) $no current flow in the circuit$ (3) $a current flow for sometime and finally it decreases to zero$ (4) $current keeps on increasing and reaches maximum after sometime$ 125. $In R - L - C series circuit, the potential differences across each element is 20 V . Now the value of the resistance alone is doubled, then P.D. across R, L and C respectively$ (1) $20 V, 10 V, 10 V$ (2) $20 V, 20 V, 20 V$ (3) $20 V, 40 V, 40 V$ (4) $10 V, 20 V, 20 V$ 126. $In an LCR circuit, at resonance$ (1) $the impedance is maximum$ (2) $the current leads the voltage by π /2$ (3) $the current and voltage are in phase$ (4) $the current is minimum.$ 127. $A copper wire of radius 0.1 mm and resistance 2 kΩ is connected across a power supply of 40 V . The number of electrons transferred per second between the supply and the wire at one end is$ (1) $2.00 \times 10^{16}$ (2) $1.25 \times 10^{17}$ (3) $2.85 \times 10^{17}$ (4) $3.25 \times 10^{16}$ 128. $A circuit when connected to an AC source of 12 V gives a current of 0.2 A. The same circuit when connected to a DC source of 12 V, gives a current of 0.4 A. The circuit is [NEET 2019]$ (1) $series LR$ (2) $series RC$ (3) $series LC$ (4) $series LCR$ 129. $In an LCR series circuit, if the angular frequency is gradually increased then match the following columns Column-I (A) Capacitive reactance (B) Inductive reactance (C) Resistance (D) Total impedance Column-II (I) will continuously increase (II) will remain constant (III) will first decrease and then increase (IV) will continuously decrease$ (1) $(A)-(I), (B)-(III), (c)-(IV), (D)-(II)$ (2) $(A)-(IV), (B)-(I), (c)-(II), (D)-(III)$ (3) $(A)-(I), (B)-(IV), (c)-(II), (D)-(III)$ (4) $(A)-(II), (B)-(III), (c)-(I), (D)-(IV)$ 130. $An alternating voltage is applied to a series LCR circuit. If the current leads the voltage by 45^{\circ}, then (tan 45^{\circ} = 1)$ (1) $X_{L} = X_{C} - R$ (2) $X_{L} = X_{C} + R$ (3) $X_{C} = X_{L}^{2} + R^{2}$ (4) $X_{L} = X_{C}^{2} + R^{2}$ 131. $In a circuit L, C and R are connected in series with an alternating voltage source of frequency f . When current in the circuit leads the voltage by 45^{\circ}, the value of C is$ (1) $\frac{1}{2 πf ( 2 πfL + R )}$ (2) $\frac{1}{2 πf ( 2 πfR + L )}$ (3) $\frac{2}{2 πf ( R + L )}$ (4) $\frac{2}{2 πf ( R + \frac{1}{L} )}$ 132. $An alternating current is given by i = (2 sin ωt + 6 cos ωt) A . The rms current (in A) is$ (1) $25$ (2) $210$ (3) $5$ (4) $102$ 133. $Capacitive reactance of a capacitor in an AC circuit is 6 kΩ . If the same capacitor is connected to an AC source of double the frequency, the capacitive reactance will become$ (1) $6 kΩ$ (2) $3 kΩ$ (3) $1.5 kΩ$ (4) $8.5 kΩ$ 134. $An alternating voltage is given by E = 100 sin (ωt + π /6) V . The voltage will be maximum for the first time when t = [T = periodic time]$ (1) $T /12$ (2) $T /2$ (3) $T /6$ (4) $T /3$ 135. $When a coil is connected to AC supply of frequency 50 Hz, a current of 4 A flows in it and it consumes 240 W power. If the potential difference across the coil is 100 V, then the inductance value of the coil is$ (1) $L = (5 π) H$ (2) $L = \frac{π}{5} H$ (3) $L = \frac{1}{5 π} H$ (4) $L = \frac{1}{25 π} H$ 136. $An alternating voltage V (t) = 220 sin 100 πt volt is applied to a purely resistive load of 50Ω . The time taken for the current to rise from half of the peak value to the peak value is:$ (1) $5 ms$ (2) $3.3 ms$ (3) $7.2 ms$ (4) $2.2 ms$ 137. $ALCR circuit is at resonance for a capacitor C, inductance L and resistance R . Now the value of resistance is halved keeping all other parameters same. The current amplitude at resonance will be now:$ (1) $Zero$ (2) $same$ (3) $halved$ (4) $double$ 138. $An electric bulb has a rated power of 50 W at 100 V . If it is used on an a.c. source 200 V, 50 Hz, a choke has to be used in series with it. This choke should have an inductance of$ (1) $0.1 mH$ (2) $1 mH$ (3) $0.1 H$ (4) $1.1 H$ 139. $Match List-I with List-II: List-I (A) ωL > \frac{1}{ωC} (B) ωL = \frac{1}{ωC} (C) ωL < \frac{1}{ωC} (D) Resonant frequency List-II (I) Current is in phase with emf (II) Current lags behind the applied emf (III) Maximum current occurs (IV) Current leads the emf Choose the correct answer from the options given below$ (1) $(A) -(II); (B) - (I); (C) - (IV); (D) - (III)$ (2) $(A) -(II); (B) - (I); (C) - (III); (D) - (IV)$ (3) $(A) -(III); (B) - (I); (C) - (IV); (D) - (II)$ (4) $(A) -(IV); (B) - (III); (C) - (II); (D) - (I)$ 140. $An LCR circuit contains resistance of 110 Ω and a supply of 220 V at 300 rad / s angular frequency. If onlycapacitance is removed from the circuit, current lags behind the voltage by 45^{\circ} . If on the other hand, only inductor is removed the current leads by 45^{\circ} with the applied voltage. The rms current flowing in the circuitwill be:$ (1) $2.5 A$ (2) $2 A$ (3) $1 A$ (4) $1.5 A$ 141. $A step down transformer connected to an AC mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit? [NEET 2021]$ (1) $0.2 A$ (2) $0.4 A$ (3) $2 A$ (4) $4 A$ 142. $An inductor of inductance L and resistor R are joined together in series and connected by a source of frequency ω . The power dissipated in the circuit is$ (1) $\frac{V}{R ^{2} + ω ^{2} L ^{2}}$ (2) $\frac{R ^{2} + ω ^{2} L ^{2}}{V}$ (3) $\frac{V ^{2} R}{R ^{2} + ω ^{2} L ^{2}}$ (4) $\frac{V ^{2} R}{R ^{2} + ω ^{2} L ^{2}}$ 143. $The current flowing through an ac circuit is given by I = 5 sin(l20 πt)A How long will the current take to reach the peak value starting from zero?$ (1) $\frac{1}{60} s$ (2) $60s$ (3) $\frac{1}{120} s$ (4) $\frac{1}{240} s$ 144. $A 20 V AC is applied to a circuit consisting of a resistor and a coil with negligible resistance. If the voltage across the resistor is 12 V, the voltage across the coil is$ (1) $16 V$ (2) $10 V$ (3) $8 V$ (4) $6 V$ 145. $An alternating voltage e = 2002 sin (100 t) volt is connected to 1 μF capacitor through a.c. ammeter. The reading of ammeter is$ (1) $5 mA$ (2) $10 mA$ (3) $15 mA$ (4) $20 mA$ 146. $A choke is preferred to a resistance for limiting current in AC circuit because$ (1) $choke is cheap$ (2) $there is no wastage of power$ (3) $choke is compact in size$ (4) $choke is a good absorber of heat.$ 147. $A small signal voltage V (t) = V_{0} sin ωt is applied across an ideal capacitor C [NEET 2016]$ (1) $over a full cycle the capacitor C does not consume any energy from the voltage source$ (2) $current I (t) is in phase with voltage V (t)$ (3) $current I(t) Ieads voltage V(t) by 180^{\circ}$ (4) $current I(t), lags voltage V(t) by 90^{\circ}$ 148. $A coil of inductance 0.1 H and resistance 110Ω is connected to a source of 110 V and 350 Hz . The phase difference between the voltage maximum and the current maximum is$ (1) $tan^{- 1} (1.5)$ (2) $tan^{- 1} (0.5)$ (3) $tan^{- 1} (1.73)$ (4) $tan^{- 1} (2)$ 149. $The impedance of an LR circuit with L = \frac{60}{π} mH, R = 8Ω and frequency 50 Hz is$ (1) $1.3Ω$ (2) $14.3Ω$ (3) $20Ω$ (4) $10Ω$ 150. $The natural frequency of an L - C circuit is 125 kHz . When the capacitor is totally filled with a dielectric material, the natural frequency decreases by 25 kHz . Dielectric constant of the material is nearly$ (1) $3.33$ (2) $2.12$ (3) $1.56$ (4) $1.91$