Alternating Current PYQs Set 7 (PDF)

Set 7 of 10 · Questions 181-210 of 290

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Mere Teacher · Previous Year Questions JEE Main Physics · Alternating Current · Set 7 (Q181-210)
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181. $An alternating voltage of frequency ' ω' is induced in electric circuit consisting of an inductance ' L' and capacitance ' C', connected in parallal. Then across the inductance coil$ (1) $current is maximum when ω^{2} = \frac{1}{LC}$ (2) $current is zero$ (3) $voltage is minimum when ω^{2} = \frac{1}{LC}$ (4) $voltage is maximum when ω^{2} = \frac{1}{LC}$ 182. $To increase the resonant frequency in series LCR circuit,$ (1) $Source frequency should be increased$ (2) $Another resistance should be added in series with the first resistance.$ (3) $Another capacitor should be added in series with the first capacitor$ (4) $The source frequency should be decreased$ 183. $In an a.c. circuit, voltage and current are given by : V = 100 sin (100 t) V and I = 100 sin (100 t + \frac{π}{3}) mA respectively. The average power dissipated in one cycle is :$ (1) $5 W$ (2) $10 W$ (3) $2.5 W$ (4) $25 W$ 184. $A resonant frequency of a current is f . If the capacitance is made four times the initial value, then the resonant frequency will become$ (1) $\frac{f}{2}$ (2) $2 f$ (3) $f$ (4) $\frac{f}{4}$ 185. $The instantaneous value of current and voltage in an AC circuit are given by I = 6 sin (100 πt + π /4) and V = 5 sin (100 πt - π /4) then$ (1) $voltage leads the current by 45^{\circ}$ (2) $current leads the voltage by 45^{\circ}$ (3) $voltage leads the current by 90^{\circ}$ (4) $current leads the voltage by 90^{\circ}$ 186. $The reactance of capacitor at 50 Hz is 5Ω . If the frequency is increased to 100 Hz, the new reactance is$ (1) $5Ω$ (2) $10Ω$ (3) $2.5Ω$ (4) $125Ω$ 187. $When an inductor L and a resistor R in series are connected across a 12 V, 50 Hz supply, a current of 0.5 A flows in the circuit. The current differs in the phase from applied voltage by \frac{π}{3} radian. Then the value of R is$ (1) $10Ω$ (2) $3Ω$ (3) $12Ω$ (4) $15Ω$ 188. $A series LCR circuit contains inductance 5 mH, capacitance 2 μF and resistance 10Ω . If a frequency A.C. source is varied, what is the frequency at which maximum power is dissipated?$ (1) $\frac{2}{π} \times 10^{5} Hz$ (2) $\frac{10 ^{5}}{π} Hz$ (3) $\frac{5}{π} \times 10^{3} Hz$ (4) $\frac{10 ^{- 5}}{π} Hz$ 189. $A resistor of 500Ω, an inductance of 0.5 H are in series with an a.c. which is given by V = 1002 sin (1000 t) . The power factor of the combination is$ (1) $\frac{1}{2}$ (2) $\frac{1}{3}$ (3) $0.5$ (4) $0.6$ 190. $A circuit of negligible resistance has an inductor of 0.16 H and capacitor of 25 μF connected in series with an alternating voltage source. The resonating frequency of the circuit is$ (1) $\frac{200}{π}$ (2) $\frac{250}{π}$ (3) $\frac{400}{π}$ (4) $\frac{150}{π}$ 191. $A resistor of 100Ω, an inductor of \frac{25}{π ^{2}} mH and a capacitor of 0.1 μF are connected in series to an ac source. The impedance of the circuit is minimum for a frequency of$ (1) $5 kHz$ (2) $10 kHz$ (3) $15 kHz$ (4) $20 kHz$ 192. $A step-up transformer operates on a 230 V line and a load current of 2 A . The ratio of primary and secondary windings is 1 : 25 . Then the current in the primary is$ (1) $25 A$ (2) $50 A$ (3) $15 A$ (4) $12.5 A$ 193. $The power factor of R - L circuit is \frac{1}{3} . If the inductive reactance is 2Ω . The value of resistance is$ (1) $0.5Ω$ (2) $\frac{1}{2} Ω$ (3) $2Ω$ (4) $2 Ω$ 194. $In an A.C. circuit, V and I are given by V = 150 sin (150 t) volt and I = 150 sin (150 t + \frac{π}{3}) ampere. The power dissipated in the circuit is$ (1) $106 W$ (2) $150 W$ (3) $5625 W$ (4) $zero$ 195. $A 12 V, 60 W lamp is connected to the secondary of a step down transformer, whose primary is connected to AC mains of 220 V. Assuming the transformer to be ideal, what is the current in the primary winding? [NEET 2023]$ (1) $2.7 A$ (2) $3.7 A$ (3) $0.37 A$ (4) $0.27 A$ 196. $A coil of inductive reactance 1/ 3 Ω and resistance 1Ω is connected to a 200 V, 50 Hz A.C. supply: The time lag between maximum voltage and current is$ (1) $\frac{1}{600} s$ (2) $\frac{1}{200} s$ (3) $\frac{1}{300} s$ (4) $\frac{1}{500} s$ 197. $A resistance R draws power P when connected to an AC source. If an inductance is now placed in series with the resistance, such that the impedance of the circuit becomes Z the power drawn will be$ (1) $P (\frac{R}{Z})^{2}$ (2) $P \frac{R}{Z}$ (3) $P (\frac{R}{Z})$ (4) $P$ 198. $In CR-circuit the growth of charge on the capacitor is$ (1) $more rapid if the CR is smaller$ (2) $more rapid if the CR is larger$ (3) $independent of CR$ (4) $independent of time$ 199. $An inductor 20 mH, a capacitor 100 μF and a resistor 50Ω are connected in series across a source of emf, V = 10 sin 314 t . The power loss in the circuit is [NEET 2018]$ (1) $0.79 W$ (2) $0.43 W$ (3) $2.74 W$ (4) $1.13 W$ 200. $In an ideal transformer, the turns ratio is \frac{N _{p}}{N _{s}} = \frac{1}{2} . The ratio V_{s} : V_{p} is equal to (the symbols carry their usual meaning) [NEET 2024]$ (1) $1 : 2$ (2) $2 : 1$ (3) $1 : 1$ (4) $1 : 4$ 201. $A capacitor and an inductance coil are connected in separate AC circuits with a bulb glowing in both the circuits. The bulb glows more brightly when$ (1) $an iron rod is introduced into the inductance coil.$ (2) $the number of turns in the inductance coil is increased$ (3) $separation between the plates of the capacitor is increased.$ (4) $a dielectric is introduced into the gap between the plates of the capacitor$ 202. $A resistor of resistance of 100Ω is connected to an AC source ϵ = 10 sin (250 π s^{- 1}) t. The energy dissipated as heat during t = 0 to t = 1 ms is approximately.$ (1) $\frac{0.57}{π} mJ$ (2) $\frac{1.141}{π} mJ$ (3) $1 mJ$ (4) $0.5 mJ$ 203. $A series resonant ac circuit contains a capacitor of 10^{- 6} F and an inductor of 10^{- 4} H . The frequency of electrical oscillations will be$ (1) $\frac{10 ^{5}}{2 π} Hz$ (2) $10^{5} Hz$ (3) $\frac{10}{2 π} Hz$ (4) $10 Hz$ 204. $A capacitor of capacitance 100 μF and a coil of resistance 20Ω and inductance 12.5 mH are connected in series with a 220 V, \frac{200}{π} Hz AC source: The maximum value of instantaneous current in the circuit is$ (1) $20 A$ (2) $10 A$ (3) $11 A$ (4) $15 A$ 205. $In the series LCR circuit shown, the impedance is$ (1) $200Ω$ (2) $100Ω$ (3) $300Ω$ (4) $500Ω$ 206. $In the A.C. circuit shown, keeping ' K' pressed, if an iron rod is inserted into the coil, the bulb in the circuit$ (1) $gets damaged$ (2) $glows less brightly$ (3) $glows with same brightness (as before the rod is inserted)$ (4) $glows more brightly$ 207. $A series LCR circuit of R = 5Ω, L = 20 mH and C = 0.5 μF is connected across an AC supply of 250V, having variable frequency. The power dissipated at resonance condition is \times 1 0^{2} W$ 208. $A series LCR circuit is connected to an AC source of 220 V, 50 Hz. The circuit contains a resistance R = 80 Ω, an inductor of inductive reactance X_{L} = 70 Ω, and a capacitor of capacitive reactance X_{c} = 130 Ω The power factor of circuit is \frac{x}{10} .The value of x is:$ 209. $A series LCR circuit with L = \frac{100}{π} mH, C = \frac{10 ^{- 3}}{π} F and R = 10Ω, is connected across an ac source of 220 V, 50 Hz supply. The power factor of the circuit would be$ 210. $A alternating current at any instant is given by i = [6 + 56 sin (100 πt + π /3)] A . The rms value of the current is A.$