STD 12 -Alternating current PYQs: JEE Mains Physics – Page 3

Showing 101–142 of 142 questions

101. 101. At very high frequencies, the effective impendance of the given circuit will be \(....\Omega\)
     2021 Hard
102. 102. Figure shows a circuit that contains four identical resistors with resistance \(R =2.0\, \Omega,\) two identical inductors with inductance \(L =2.0 \,mH\) and an ideal battery with \(e m f E =9 \,V .\) The current \('i'\) just after the switch \('S'\) is closed will be .... \(A\)
     2021 Hard
103. 103. Find the peak current and resonant frequency of the following circuit (as shown in figure).
     2021 Hard
104. 104. For a series \(LCR\) circuit with \({R}=100\,\ \Omega, {L}=0.5\, {mH}\) and \({C}=0.1\, {pF}\) connected across \(220 \,{V}-50\, {Hz}\) \(AC\) supply, the phase angle between current and supplied voltage and the nature of the circuit is : 2021 Medium
105. 105. In a scries \(LCR\) resonance circuit, if we change the resistance only, from a lower to higher value 2021 Medium
106. 106. In a series \(LCR\) circuit, the inductive reactance \(\left( X _{ L }\right)\) is \(10\, \Omega\) and the capacitive reactance \(\left( X _{ C }\right)\) is \(4\, \Omega\). The resistance \(( R )\) in the circuit is \(6\, \Omega\). The power factor of the circuit is : 2021 Medium
107. 107. In a series \(LCR\) resonant circuit, the quality factor is measured as \(100\) If the inductance is increased by two fold and resistance is decreased by two fold, then the quality factor after this change will be ......... 2021 Hard
108. 108. In an ac circuit, an inductor, a capacitor and a resistor are connected in series with \({X}_{{L}}={R}={X}_{{C}}\). Impedance of this circuit is: 2021 Easy
109. 109. In an \(LCR\) series circuit, an inductor \(30 \,{mH}\) and a resistor \(1 \, \Omega\) are connected to an \(AC\) source of angular frequency \(300 \, {rad} / {s}\). The value of capacitance for which, the current leads the voltage by \(45^{\circ}\) is \(\frac{1}{x} \times 10^{-3} \, {F}\). Then the value of \(x\) is ..... . 2021 Hard
110. 110. In the given circuit the \({AC}\) source has \(\omega=100\, {rad} {s}^{-1}\). Considering the inductor and capacitor to be ideal, what will be the current \(I\) flowing through the circuit? (in \(A\))
     2021 Hard
111. 111. Match List\(-I\) with List\(-II\) :

     List\(-I\)	List\(-II\)
     \((a)\) \(\omega L\,>\,\frac{1}{\omega C}\)	\((i)\) Current is in phase with \(emf\)
     \((b)\) \(\omega {L}=\frac{1}{\omega {C}}\)	\((ii)\) Current lags behind the applied \(emf\)
     \((c)\) \(\omega {L}\, < \,\frac{1}{\omega {C}}\)	\((iii)\) Maximum current occurs
     \((d)\) resonant frequency	\((iv)\) Current leads the \(emf\)

     Choose the correct answer from the options given below : 2021 Medium
112. 112. Match List\(-I\) with List\(-II\)

     List\(-I\)	List\(-II\)
     \((a)\) Phase difference between current and voltage in a purely resistive \(AC\) circuit	\((i)\) \(\frac{\pi}{2} ;\) current leads voltage
     \((b)\) Phase difference between current and voltage in a pure inductive \(AC\) circuit	\((ii)\) zero
     \((c)\) Phase difference between current and voltage in a pure capacitive \(AC\) circuit	\((iii)\) \(\frac{\pi}{2} ;\) current lags voltage
     \((d)\) Phase difference between current and voltage in an \(LCR\) series circuit	\((iv)\) \(\tan ^{-1}\left(\frac{X_{C}-X_{L}}{R}\right)\)

     Choose the most appropriate answer from the options given below: 2021 Medium
113. 113. The alternating current is given by \({i}=\left\{\sqrt{42} \sin \left(\frac{2 \pi}{{T}} {t}\right)+10\right\} {A}\) The \(r.m.s.\) value of this current is \({A}\) 2021 Hard
114. 114. The angular frequency of alternating current in a \(L-C-R\) circuit is \(100\, rad / s\). The components connected are shown in the figure. Find the value of inductance of the coil and capacity of condenser.
     2021 Hard
115. 115. Two circuit are shown in the figure \((a)\) and \((b).\) At a frequency of \(....\,rad/s\) the average power dissipated in one cycle will be same in both the circuits.
     2021 Hard
116. 116. What happens to the inductive reactance and the current in a purely inductive circuit if the frequency is halved ? 2021 Medium
117. 117. A \(750\, Hz,\) \(20\) \(V\) (rms ) source is connected to a resistance of \(100\, \Omega\) an inductance of \(0.1803\, H\) and a capacitance of \(10\mu ,\) \(F\) all in series. The time in which the resistance (heat capacity \(2 J /{ }^{\circ} C\) ) will get heated by \(10^{\circ} C\). (assume no \(105 s\) of heat to the surroundings) is close to\(.....s\) 2020 Hard
118. 118. An \(AC\) circuit has \(R =100 \Omega, C =2\, \mu F\) and \(L =80\, mH ,\) connected in series. The quality factor of the circuit is\(.......\) 2020 Medium
119. 119. An inductance coil has a reactance of \(100\, \Omega\). When an \(AC\) signal of frequency \(1000\, Hz\) is applied to the coil, the applied voltage leads the current by \(45^{\circ}\). The self- inductance of the coil is 2020 Hard
120. 120. In a scries \(LR\) circuit, power of \(400\, W\) is dissipated from a source of \(250\, V , 50\, Hz\). The power factor of the circuit is \(0.8 .\) In order to bring the power factor to unity, a capacitor of value \(C\) is added in series to the \(L\) and \(R\). Taking the value of \(C\) as \(\left(\frac{ n }{3 \pi}\right) \mu F ,\) then value of \(n\) is\(......\) 2020 Medium
121. 121. In \(LC\) circuit the inductance \(\mathrm{L}=40\; \mathrm{mH}\) and capacitance \(\mathrm{C}=100\; \mu \mathrm{F} .\) If a voltage \(\mathrm{V}(\mathrm{t})=10 \sin (314 \mathrm{t})\) is applied to the circuit, the current in the circuit is given as  2020 Hard
122. 122. A \(20\, Henry\) inductor coil is connected to a \(10\, ohm\) resistance in series as shown in figure. The time at which rate of dissipation of energy (Joule’s heat) across resistance is equal to the rate at which magnetic energy is stored in the inductor, is
     2019 Hard
123. 123. A circuit connected to an \(ac\) source of \(emf\) \(e = e_0\, sin\, (1000t)\) with \(t\) in seconds, gives a phase difference of \(\frac{\pi }{4}\) between the \(emf\) \(e\) and current \(i\). Which of the following circuits will exhibit this? 2019 Hard
124. 124. A series \(AC\) circuit containing an inductor \((20\,mH),\) a capacitor \((120\,\mu F)\) and a resistor \((60\, \Omega )\) is driven by an \(AC\) source of \(24\,V/50\,Hz.\) The energy dissipated in the circuit in \(60\,s\) is 2019 Medium
125. 125. An alternating voltage \(v\left( t \right) = 220\,\sin \,100\pi l\,volt\) is applied to a purely resistive load of \(50\,\Omega \) . The time taken for the current to rise from half of the peak value of the peak value is.....\(ms\) 2019 Medium
126. 126. Consider the \(LR\) circuit shown in the figure. If the switch \(S\) is closed at \(t = 0\) then the amount of charge that passes through the battery between \(t = 0\) and \(t = \frac{L}{R}\) is
     2019 Hard
127. 127. In the below circuit, \(C\, = \,\frac{{\sqrt 3 }}{2}\,\mu F,\,R = 20\,\,\Omega ,\,L = \frac{{\sqrt 3 }}{{10}}H\) and \({R_1} = 10\,\,\Omega .\) Current in \(L-R_1\) path is \(I_1\) and \(C-R_2\) path is \(I_2.\) The voltage of \(A.C\) source is given by, \(V\, = \,200\sqrt 2 \,\sin \,(100\,t)\,volts.\) The phase difference between \(I_1\) and \(I_2\) is
     2019 Hard
128. 128. In the figure shown, a circuit contains two identical resistors with resistance \(R = 5\,\Omega \) and an inductance with \(L = 2\, mH\). An ideal battery of \(15\, V\) is connected in the circuit. What will be the current through the battery long after the switch is closed?......\(A\)
     2019 Medium
129. 129. For an \(RLC\) circuit driven with voltage of amplitude \(v_m\) and frequency \({\omega _0} = \frac{1}{{\sqrt {LC} }}\) the current exhibits resonance. The quality factor, \(Q\) is given by: 2018 Easy
130. 130. In an \(A.C.\) circuit, the instantaneous \(e.m.f\) and current are given by. \(e=100\) \(sin\) \(20t\) \(i=20sin\) \(\left( {30t - \frac{\pi }{4}} \right)\) In one cycle of \(A.C.\), the average power consumed by the circuit and the wattless current are, respectively 2018 Medium
131. 131. A sinusoidal voltage of peak value \(283\, V\) and angular frequency \(320/s\) is applied to a series \(LCR\) circuit. Given that \(R\, = 5\,\Omega \) , \(L\,= 25\, mH\) and \(C\, = 1000\, \mu F\). The total impedance, and phase difference between the voltage across the source and the current will respectively be 2017 Hard
132. 132. An arc lamp requires a direct current of \(10\ A\) at \(80\ V\) to function. If it is connected to a \( 220\ V (rms ), 50\ Hz\ AC\) supply, the series inductor needed for it to work is close to : 2016 Medium
133. 133. For the \(LCR\) circuit, shown here, the current is observed to lead the applied voltage. An additional capacitor \(C '\) , when joined with the capacitor \(C\) present in the circuit , makes the power factor of the circuit unity. The capacitor \(C'\), must have been connected in
     2015 Hard
134. 134. The \(AC\) voltage across a resistance can be measured using a 2015 Easy
135. 135. A sinusoidal voltage \(V(t) = 100\,sin\,(500t)\) is applied across a pure inductance of \(L = 0.02\,H.\) The current through the coil is 2014 Medium
136. 136. When the \(rms\) voltages \(V_L, V_C\) and \(V_R\) are measured respectively across the inductor \(L\), the capacitor \(C\) and the resistor \(R\) in a series \(LCR\) circuit connected to an \(AC\) source, it is found that the ratio \(V_L : V_C : V_R = 1 : 2 : 3\). If the \(rms\) voltage of the \(AC\) sources is \(100\, V\), the \(V_R\) is close to........\(V\) 2014 Hard
137. 137. A series \(LR\) circuit is connected to an ac source of frequency \(\omega \) and the inductive reactance is equal to \(2R\). A capacitance of capacitive reactance equal to \(R\) is added in series with \(L\) and \(R\). The ratio of the new power factor to the old one is 2013 Hard
138. 138. An \(LCR\) circuit as shown in the figure is connected to a voltage source \(V_{ac}\) whose frequency can be varied. The frequency, at which the voltage across the resistor is maximum, is......\(Hz\)
     2013 Easy
139. 139. In a series \(L-C-R\) circuit, \(C = 10^{-11}\,Farad.\) \(L = 10^{-5}\,Henry\) and \(R =100\,Ohm.\) when a constant \(D.C.\) voltage \(E\) is applied to the circuit, the capacitor acquires a charge \(10^{-9}\,C\) .The \(D.C.\) source is replaced by a sinusoidal voltage source in which the peak voltage \(E_0\) is equal to the constant \(D.C.\) voltage \(E.\) At resonance the peak value of the charge acquired by the capacitor will be 2013 Hard
140. 140. In the circuit shown here, the voltage across \(L\) and \(C\) are respectively \(300\, V\) and \(400\, V\). The voltage \(E\) of the ac source is......\(Volt\)
     2013 Easy
141. 141. The plot given below is of the average power delivered to an \(LRC\) circuit versus frequency. The quality factor of the circuit is
     2013 Medium
142. 142. When resonance is produced in a series \(LCR\) circuit, then which of the following is not correct ? 2013 Medium

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