Alternating Current PYQs Set 6 (PDF)

Set 6 of 10 · Questions 151-180 of 290

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Mere Teacher · Previous Year Questions JEE Main Physics · Alternating Current · Set 6 (Q151-180)
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151. $In a half wave rectifier, the AC input source of frequency 50 Hz is used. The fundamental frequency of the output is$ (1) $50 Hz$ (2) $150 Hz$ (3) $200 Hz$ (4) $75 Hz$ 152. $An AC current is given by the expression, I (t) = 50 sin (200 πt) in amperes, The frequency and r.m.s value of the current respectively are$ (1) $100 Hz, 502 A$ (2) $100 Hz, 252 A$ (3) $200 Hz, 502 A$ (4) $200 Hz, 252 A$ 153. $Given below are two statements: Statement I: An AC circuit undergoes electrical resonance if it contains either a capacitor or an inductor. Statement II: An AC circuit containing a pure capacitor or a pure inductor consumes high power due to its non-zero power factor. In the light of above statements, choose the correct answer from the options given below:$ (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) $Both Statement I and Statement II are true$ 154. $A parallel plate capacitor has a capacitance C = 200 pF . It is connected to 230 V ac supply with an angular frequency 300 rad / s . The rms value of conduction current in the circuit and displacement current in the capacitor respectively are:$ (1) $1.38 μA and 1.38 μA$ (2) $14.3 μA and 143 μA$ (3) $13.8μA and 138 μA$ (4) $13.8 μA and 13.8 μA$ 155. $A small signal voltage V(t) = V_{0} sinωt is applied across an ideal capacitor C:$ (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) $Current I(t) is in phase with voltage V(t)$ 156. $A series LCR circuit driven by 300 V at a frequency of 50 Hz contains a resistance R = 3 kΩ an inductor of inductive reactance X_{L} = 250 πΩ and an unknown capacitor. The value of capacitance to maximize the average power should be: (Take π^{2} = 10)$ (1) $4 μ F$ (2) $25 μ F$ (3) $400 μ F$ (4) $40 μ F$ 157. $In an LC oscillator, if values of inductance and capacitance become twice and eight times, respectively, then the resonant frequency of oscillator becomes x times its initial resonant frequency ω_{0} . The value of x is:$ (1) $1/4$ (2) $16$ (3) $1/16$ (4) $4$ 158. $In series LCR circuit, the capacitance is changed from C to 4 C . To keep the resonance frequency unchanged, the new inductance should be:$ (1) $reduced by \frac{1}{4} L$ (2) $increased by 2 L$ (3) $reduced by \frac{3}{4} L$ (4) $increased to 4 L$ 159. $An AC current is given by I = I_{1} sin ωt + I_{2} cos ωt . A hot wire ammeter will give a reading:$ (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) $\frac{I _{1}^{2} + I _{2}^{2}}{2 2}$ 160. $In Karnataka, the normal domestic power supply AC is 220 V, 50 Hz . Here 220 V and 50 Hz refer to$ (1) $peak value of voltage and frequency$ (2) $rms value of voltage and frequency$ (3) $mean value of voltage and frequency$ (4) $peak value of voltage and angular frequency.$ 161. $In an oscillating LC circuit, the maximum charge on the capacitor is Q . The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is$ (1) $\frac{Q}{2}$ (2) $\frac{Q}{3}$ (3) $Q$ (4) $\frac{Q}{2}$ 162. $A coil has a resistance of 30Ω and an inductive reactance of 20Ω at 50 Hz frequency. If an AC source of 200 V, 100 Hz is connected across the coil, the current in the coil is$ (1) $2 A$ (2) $\frac{20}{13} A$ (3) $4 A$ (4) $8 A$ 163. $In an ideal step up transformer, if the input voltage and input power are V_{1} and P_{1} respectively and the output voltage and output power are V_{2} and P_{2} respectively, then$ (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) $V_{1} < V_{2}; P_{1} = P_{2}$ 164. $A coil having an inductance of \frac{1}{π} H is connected in series with a resistance of 300Ω . If 20 V from a 200 Hz source are impressed across the combination, the value of the phase angle between the voltage and the current is$ (1) $tan^{- 1} (\frac{5}{4})$ (2) $tan^{- 1} (\frac{4}{5})$ (3) $tan^{- 1} (\frac{3}{4})$ (4) $tan^{- 1} (\frac{4}{3})$ 165. $A step down transformer has 50 turns on secondary and 1000 turns on primary winding. If a transformer is connected to 220 V and 1 A A.C. source, what is output current of the transformer?$ (1) $100 A$ (2) $1 20 A$ (3) $2 A$ (4) $20 A$ 166. $Two inductors A and B when connected in parallel are equivalent to a single inductor of inductance 1.5 H and when connected in series are equivalent to a single inductor of inductance 8 H . Find the difference in the inductances of A and B .$ (1) $3 H$ (2) $7.5 H$ (3) $2 H$ (4) $4 H$ 167. $The energy stored in a 50 mH inductor carrying a current of 4 A is$ (1) $0.4 J$ (2) $4.0 J$ (3) $0.8 J$ (4) $0.04 J$ 168. $A sinusoidal voltage V(t) = 210 sin 3000t volt is applied to a series LCR circuit in which L = 10 mH, C = 25 μ F and R = 100 Ω . The phase difference (Φ) between the applied voltage and resultant current will be:$ (1) $t a n^{- 1} (0.17)$ (2) $t a n^{- 1} (9.46)$ (3) $t a n^{- 1} (0.30)$ (4) $t a n^{- l} (13.33)$ 169. $The frequency of an alternating current is 50 Hz . What is the minimum time taken by current to reach its peak value from rms value?$ (1) $0.02 s$ (2) $5 \times 10^{- 3} s$ (3) $10 \times 10^{- 3} s$ (4) $2.5\times 1 0^{- 3} s$ 170. $A coil is connected to an AC source with peak emf, 8 V and frequency \frac{30}{π} Hz . The coil has resistance of 8Ω . If the average power dissipated by the coil is 0.4 W, then the inductance of the coil is$ (1) $0.8 H$ (2) $2.0 H$ (3) $1.4 H$ (4) $0.4 H$ 171. $In a series LCR circuit, the potential drop across L, C and R respectively are 40 V, 120 V and 60 V . Then the source voltage is$ (1) $220 V$ (2) $160 V$ (3) $180 V$ (4) $100 V$ 172. $In an AC circuit, the current is i = 5 sin (100 t - \frac{π}{2}) A and voltage is e = 200 sin (100 t) volt. Power consumption in the circuit is (cos 90^{\circ} = 0)$ (1) $200 W$ (2) $0 W$ (3) $40 W$ (4) $1000 W$ 173. $For a purely inductive or a purely capacitive circuit, the power factor is$ (1) $zero$ (2) $0.5$ (3) $1$ (4) $\infty$ 174. $In a series LCR circuit, an alternating emf (v) and current (i) are given by the equation v = v_{0} sin ωt, i = i_{0} sin (ωt + \frac{π}{3}) . The average power dissipated in the circuit over a cycle of AC is$ (1) $\frac{v _{0} i _{0}}{2}$ (2) $\frac{v _{0} i _{0}}{4}$ (3) $\frac{3}{2} v_{0} i_{0}$ (4) $Zero$ 175. $Match List-I with List-II List-I (A) AC generator (B) Galvanometer (C) Transformer (D) Metal detector List-II (I) Detects the presence of current in the circuit (II) Converts mechanical energy into electrical energy (III) Works on the principle of resonance in AC circuit (IV) Changes an alternating voltage for smaller or greater value Choose the correct answer from the options given below:-$ (1) $(A)-(II), (B)-(I), (C)-(IV), (D)-(III)$ (2) $(A)-(II), (B)-(I), (C)-(III), (D)-(IV)$ (3) $(A)-(III), (B)-(IV), (C)-(III), (D)-(I)$ (4) $(A)-(III), (B)-(I), (C)-(II), (D)-(IV)$ 176. $In series LCR circuit R = 18Ω and impedance is 33Ω . An rms voltage 220 V is applied across the circuit. The true power consumed in a.c. circuit is$ (1) $220 W$ (2) $400 W$ (3) $600 W$ (4) $800 W$ 177. $An inductor and a resistor of 25Ω are connected in series to an ac source of voltage 100 sin (100 πt) volt. If the impedance of the circuit is 50Ω, the average power dissipated per cycle in the circuit is$ (1) $10 W$ (2) $25 W$ (3) $50 W$ (4) $100 W$ 178. $In a fluorescent lamp choke (a small transformer) 100 V of reverse voltage is produced when the choke current changes uniformly from 0.25 A to 0 in a duration of 0.025 ms. The self-inductance of the choke (in mH) is estimated to be:$ 179. $A series LCR circuit consists of R = 80 Ω X_{L} = 100 Ω, and X_{C} = 40 Ω . The input voltage is 2500 cos(100 π t) V. The amplitude of current, in the circuit, is __________ A.$ 180. $An alternating emf E = 1102 sin 100 t volt is applied to a capacitor of 2 μF, the rms value of current in the circuit is______mA,$