Alternating Current PYQs Set 5 (PDF)

Set 5 of 9 · Questions 121-150 of 244

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Mere Teacher · Previous Year Questions NEET Physics · Alternating Current · Set 5 (Q121-150)
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121. $A step down transformer connected to an AC mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit? [NEET 2021]$ (1) $0.2 A$ (2) $0.4 A$ (3) $2 A$ (4) $4 A$ 122. $An inductor of inductance L and resistor R are joined together in series and connected by a source of frequency ω . The power dissipated in the circuit is$ (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) $\frac{V ^{2} R}{R ^{2} + ω ^{2} L ^{2}}$ 123. $The current flowing through an ac circuit is given by I = 5 sin(l20 πt)A How long will the current take to reach the peak value starting from zero?$ (1) $\frac{1}{60} s$ (2) $60s$ (3) $\frac{1}{120} s$ (4) $\frac{1}{240} s$ 124. $A 20 V AC is applied to a circuit consisting of a resistor and a coil with negligible resistance. If the voltage across the resistor is 12 V, the voltage across the coil is$ (1) $16 V$ (2) $10 V$ (3) $8 V$ (4) $6 V$ 125. $An alternating voltage e = 2002 sin (100 t) volt is connected to 1 μF capacitor through a.c. ammeter. The reading of ammeter is$ (1) $5 mA$ (2) $10 mA$ (3) $15 mA$ (4) $20 mA$ 126. $A choke is preferred to a resistance for limiting current in AC circuit because$ (1) $choke is cheap$ (2) $there is no wastage of power$ (3) $choke is compact in size$ (4) $choke is a good absorber of heat.$ 127. $A small signal voltage V (t) = V_{0} sin ωt is applied across an ideal capacitor C [NEET 2016]$ (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) $current I(t), lags voltage V(t) by 90^{\circ}$ 128. $A coil of inductance 0.1 H and resistance 110Ω is connected to a source of 110 V and 350 Hz . The phase difference between the voltage maximum and the current maximum is$ (1) $tan^{- 1} (1.5)$ (2) $tan^{- 1} (0.5)$ (3) $tan^{- 1} (1.73)$ (4) $tan^{- 1} (2)$ 129. $The impedance of an LR circuit with L = \frac{60}{π} mH, R = 8Ω and frequency 50 Hz is$ (1) $1.3Ω$ (2) $14.3Ω$ (3) $20Ω$ (4) $10Ω$ 130. $The natural frequency of an L - C circuit is 125 kHz . When the capacitor is totally filled with a dielectric material, the natural frequency decreases by 25 kHz . Dielectric constant of the material is nearly$ (1) $3.33$ (2) $2.12$ (3) $1.56$ (4) $1.91$ 131. $In a half wave rectifier, the AC input source of frequency 50 Hz is used. The fundamental frequency of the output is$ (1) $50 Hz$ (2) $150 Hz$ (3) $200 Hz$ (4) $75 Hz$ 132. $An AC current is given by the expression, I (t) = 50 sin (200 πt) in amperes, The frequency and r.m.s value of the current respectively are$ (1) $100 Hz, 502 A$ (2) $100 Hz, 252 A$ (3) $200 Hz, 502 A$ (4) $200 Hz, 252 A$ 133. $Given below are two statements: Statement I: An AC circuit undergoes electrical resonance if it contains either a capacitor or an inductor. Statement II: An AC circuit containing a pure capacitor or a pure inductor consumes high power due to its non-zero power factor. In the light of above statements, choose the correct answer from the options given below:$ (1) $Statement I is false but statement II is true$ (2) $Statement I is true but statement II is false$ (3) $Both Statement I and Statement II are false$ (4) $Both Statement I and Statement II are true$ 134. $A parallel plate capacitor has a capacitance C = 200 pF . It is connected to 230 V ac supply with an angular frequency 300 rad / s . The rms value of conduction current in the circuit and displacement current in the capacitor respectively are:$ (1) $1.38 μA and 1.38 μA$ (2) $14.3 μA and 143 μA$ (3) $13.8μA and 138 μA$ (4) $13.8 μA and 13.8 μA$ 135. $A small signal voltage V(t) = V_{0} sinωt is applied across an ideal capacitor C:$ (1) $Current I(t), leads voltage V(t) by 180°$ (2) $Current I(t), lags voltage V(t) by 90°$ (3) $Over a full cycle the capacitor C does not consume any energy from the voltage source.$ (4) $Current I(t) is in phase with voltage V(t)$ 136. $A series LCR circuit driven by 300 V at a frequency of 50 Hz contains a resistance R = 3 kΩ an inductor of inductive reactance X_{L} = 250 πΩ and an unknown capacitor. The value of capacitance to maximize the average power should be: (Take π^{2} = 10)$ (1) $4 μ F$ (2) $25 μ F$ (3) $400 μ F$ (4) $40 μ F$ 137. $In an LC oscillator, if values of inductance and capacitance become twice and eight times, respectively, then the resonant frequency of oscillator becomes x times its initial resonant frequency ω_{0} . The value of x is:$ (1) $1/4$ (2) $16$ (3) $1/16$ (4) $4$ 138. $In series LCR circuit, the capacitance is changed from C to 4 C . To keep the resonance frequency unchanged, the new inductance should be:$ (1) $reduced by \frac{1}{4} L$ (2) $increased by 2 L$ (3) $reduced by \frac{3}{4} L$ (4) $increased to 4 L$ 139. $An AC current is given by I = I_{1} sin ωt + I_{2} cos ωt . A hot wire ammeter will give a reading:$ (1) $\frac{I _{1}^{2} - I _{2}^{2}}{2}$ (2) $\frac{I _{1}^{2} + I _{2}^{2}}{2}$ (3) $\frac{I _{1}^{2} + I _{2}^{2}}{2}$ (4) $\frac{I _{1}^{2} + I _{2}^{2}}{2 2}$ 140. $In Karnataka, the normal domestic power supply AC is 220 V, 50 Hz . Here 220 V and 50 Hz refer to$ (1) $peak value of voltage and frequency$ (2) $rms value of voltage and frequency$ (3) $mean value of voltage and frequency$ (4) $peak value of voltage and angular frequency.$ 141. $In an oscillating LC circuit, the maximum charge on the capacitor is Q . The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is$ (1) $\frac{Q}{2}$ (2) $\frac{Q}{3}$ (3) $Q$ (4) $\frac{Q}{2}$ 142. $A coil has a resistance of 30Ω and an inductive reactance of 20Ω at 50 Hz frequency. If an AC source of 200 V, 100 Hz is connected across the coil, the current in the coil is$ (1) $2 A$ (2) $\frac{20}{13} A$ (3) $4 A$ (4) $8 A$ 143. $In an ideal step up transformer, if the input voltage and input power are V_{1} and P_{1} respectively and the output voltage and output power are V_{2} and P_{2} respectively, then$ (1) $V_{1} = V_{2}; P_{1} = P_{2}$ (2) $V_{1} > V_{2}; P_{1} > P_{2}$ (3) $V_{1} < V_{2}; P_{1} < P_{2}$ (4) $V_{1} < V_{2}; P_{1} = P_{2}$ 144. $A coil having an inductance of \frac{1}{π} H is connected in series with a resistance of 300Ω . If 20 V from a 200 Hz source are impressed across the combination, the value of the phase angle between the voltage and the current is$ (1) $tan^{- 1} (\frac{5}{4})$ (2) $tan^{- 1} (\frac{4}{5})$ (3) $tan^{- 1} (\frac{3}{4})$ (4) $tan^{- 1} (\frac{4}{3})$ 145. $A step down transformer has 50 turns on secondary and 1000 turns on primary winding. If a transformer is connected to 220 V and 1 A A.C. source, what is output current of the transformer?$ (1) $100 A$ (2) $1 20 A$ (3) $2 A$ (4) $20 A$ 146. $Two inductors A and B when connected in parallel are equivalent to a single inductor of inductance 1.5 H and when connected in series are equivalent to a single inductor of inductance 8 H . Find the difference in the inductances of A and B .$ (1) $3 H$ (2) $7.5 H$ (3) $2 H$ (4) $4 H$ 147. $The energy stored in a 50 mH inductor carrying a current of 4 A is$ (1) $0.4 J$ (2) $4.0 J$ (3) $0.8 J$ (4) $0.04 J$ 148. $A sinusoidal voltage V(t) = 210 sin 3000t volt is applied to a series LCR circuit in which L = 10 mH, C = 25 μ F and R = 100 Ω . The phase difference (Φ) between the applied voltage and resultant current will be:$ (1) $t a n^{- 1} (0.17)$ (2) $t a n^{- 1} (9.46)$ (3) $t a n^{- 1} (0.30)$ (4) $t a n^{- l} (13.33)$ 149. $The frequency of an alternating current is 50 Hz . What is the minimum time taken by current to reach its peak value from rms value?$ (1) $0.02 s$ (2) $5 \times 10^{- 3} s$ (3) $10 \times 10^{- 3} s$ (4) $2.5\times 1 0^{- 3} s$ 150. $A coil is connected to an AC source with peak emf, 8 V and frequency \frac{30}{π} Hz . The coil has resistance of 8Ω . If the average power dissipated by the coil is 0.4 W, then the inductance of the coil is$ (1) $0.8 H$ (2) $2.0 H$ (3) $1.4 H$ (4) $0.4 H$