CBSE Questions for Class 12 Medical Physics Alternating Current Quiz 4 - MCQExams.com

Figure shows a series LCR circuit connected to a variable frequency 200V source. The source frequency which drives the circuit at resonance is

22699.jpg
  • 50 Hz
  • (50 /$$\pi$$ )Hz
  • 25 Hz
  • (25 /$$\pi$$ ) Hz
A 100$$\Omega $$ resistance is connected in series with a 4H inductor. The voltage across the resistor is $$V_{R}=2sin(1000t)V$$. The voltage across the inductor is:
  • $$80sin\left ( 1000t+\dfrac{\pi }{2} \right )$$
  • $$40sin\left ( 1000t+\dfrac{\pi }{2} \right )$$
  • $$80sin\left ( 1000t-\dfrac{\pi }{2} \right )$$
  • $$40sin\left ( 1000t-\dfrac{\pi }{2} \right )$$
In the following circuit, the values of current flowing in the circuit at f=0 and f=$$\infty$$ will respectively be
22715.jpg
  • 8A and 0A
  • 0A and 0A
  • 8A and 8A
  • 0A and 8A
The inductive reactance of a coil is  $$1000\Omega .$$ If its self inductance and frequency both are increased two  times, then inductive reactance will be
  • $$1000 \Omega$$
  • $$2000 \Omega$$
  • $$4000 \Omega$$
  • $$16000 \Omega$$
A condenser of 10 $$\mu$$F and an inductor of 1H are connected in series with an A.C. source of frequency 50Hz. The impedance of the combination will be (take $$\pi^{2}$$ $$=$$10 ):
  • zero
  • Infinity
  • 44.7$$\Omega $$
  • 5.67$$\Omega $$
In an L-C-R series circuit, $$R=\sqrt{5}\Omega ,X_{L}=9\Omega ,X_{C}=7\Omega $$. If applied voltage in the circuit is 50V then impedance of the circuit in ohm will be
  • $$2$$
  • $$3$$
  • $$2\sqrt{5}$$
  • $$3\sqrt{5}$$
A coil of inductance 0.1H is connected to 50V, 100Hz generator and current is found to be 0.5A. The potential difference across resistance of the coil is
  • 15V
  • 20V
  • 25V
  • 39V
In an LR circuit, R $$=$$ 10 $$\Omega $$ and L $$=$$ 2H. If an alternating voltage of 120V and 60Hz is connected in this circuit, then the value of current flowing in it will be _______ A (nearly)
  • 0.32
  • 0.16
  • 0.48
  • 0.8
A 220V, 50Hz a.c. generator is connected to an inductor and a 50$$\Omega $$ resistance in series. The current in the circuit is 1.0A. The P.D. across the inductor is:
  • 102.2 V
  • 186.4 V
  • 214.24 V
  • 302 V
A circuit operating at $$\dfrac{360}{2\pi }$$ Hz $$\Omega $$ contains a 1 F $$\mu $$ capacitor and a 20 resistor. The inductor must be added in series to make the phase angle for the circuit zero is
  • 7.7 H
  • 10 H
  • 3.5 H
  • 15 H
In the series L-C-R circuit figure, the voltmeter and ammeter readings are
22718_7c7387c095a248f59c4167301a1c951d.png
  • $$V $$=$$ 100 volt, I $$=$$ 2 amp$$
  • $$V $$=$$ 100 volt, I $$=$$ 5 amp$$
  • $$V $$=$$1000 volt, I $$=$$ 2 amp$$
  • $$V $$=$$ 300 volt, I$$=$$1 amp$$
A resistor $$R$$ and capacitor $$ C$$ are connected in series across an AC source of rms voltage $$5 V$$. If the rms voltage across $$C$$ is $$3 V$$ then that across $$R$$ is :
  • $$1V$$
  • $$2V$$
  • $$3V$$
  • $$4V$$
The potential difference between the ends of a resistance R is $$V_{R}$$, between the ends of capacitor is $$V_{C}$$ $$=$$ 2$$V_{R}$$ and between the ends of inductance is $$V_{L}$$ $$=$$ 3$$V_{R}$$ then the alternating potential of the source in terms of $$V_{R}$$ will be:
  • $$\sqrt{2}V_{R}$$
  • $$V_{R}$$
  • $$\dfrac{V_{R}}{\sqrt{2}}$$
  • $$5V_{R}$$
The natural frequency of an LC - circuit is $$1,25,000$$ cycles per second. Then the capacitor C is replaced by another capacitor with a dielectric medium of dielectric constant k. In this case, the frequency decreases by $$25 kHz$$. The value of k is:
  • $$1.56$$
  • $$1.7$$
  • $$3.0$$
  • $$2.1$$
At resonance, the angle $$\phi$$ is
  • $$\displaystyle \frac{\pi}{4}$$
  • $$\displaystyle \frac{\pi}{2}$$
  • $$\displaystyle \frac{\pi}{6}$$
  • zero
The reading of voltmeter and ammeter in the following figure will respectively be :

22714_dbe1df9a62bb47e3b71121b3bb027f49.jpg
  • 0 and 2A
  • 2A and 0V
  • 2V and 2A
  • 0V and 0A
In the following diagram, the value of emf of A.C. source will be :
22732.png
  • $$40 V$$
  • $$40\sqrt{2}V$$
  • $$\dfrac{40}{\sqrt{2}}V$$
  • $$160 V$$
An inductance of 0.2 H and a resistance of 100$$\Omega $$ are connected in series to an A.C. 180 V, 50 Hz supply. The apparent current flowing in the circuit will be
  • 0.525 A
  • 5.25 A
  • 1.525 A
  • 15.25 A
An $$LCR$$ circuit has $$L=10\ mH, R=3\Omega$$, and $$C =1\mu$$ $$F$$ connected in series to a source of $$15 \cos\omega t$$ volt. The current amplitude at a frequency that is $$10\%$$ lower than the resonant frequency is:
  • $$0.5 A$$
  • $$0.7 A$$
  • $$0.9 A$$
  • $$1.1 A$$
In the circuit shown in the figure, (neglecting source resistance) the voltmeter and ammeter readings will respectively be

22736.png
  • 0 V, 8 A
  • 150 V, 8 A
  • 150 V, 3 A
  • 0 V, 3 A
In a series LCR circuit the voltage across resistance, capacitance and inductance is 10 V each. If the capacitance is short circuited, the voltage across the inductance will be
  • $$10 V$$
  • $$(10/\sqrt{2}V)$$
  • $$(10/\sqrt{3}V)$$
  • $$20 V$$
In the following circuit, the potential of source is $$E_0=200$$ volts, $$R=200\Omega$$, $$L=0.1$$ henry, $$C=10.6 $$ farad and frequency is variable, then the current at f=0 and f=$$\infty$$ is :
22740.jpg
  • 0A, 10A
  • 10A, 0A
  • 10A, 10A
  • 0A, 0A
The values of $$X_{L}, X_{C}$$ and R in series with an A.C.  circuit are 8$$\Omega $$ , 6$$\Omega $$ and 10$$\Omega $$ respectively. The
total impedance of the circuit will be ________$$\Omega $$
  • $$10.2$$
  • $$12.2$$
  • $$10$$
  • $$24.4$$
A condenser and a 30 $$\Omega $$ resistance are connected in series. When they are connected to 120V A.C. source then the current flowing in the circuit is 1A The p.d. across the ends of the condenser will be nearly
  • 1 V
  • 116 V
  • zero
  • 220 V
An LCR series circuit with 100 $$\Omega $$ resistance is connected to an ac source of 200V and of frequency of 300 rad/s. When only the capacitance is removed, the current lags behind the voltage by $$60^{0}$$ . When only the inductance is removed, the current leads the voltage by $$60^{0}$$ the current through the circuit is:
  • 1 A
  • 2 A
  • 3 A
  • 4 A
In the given figure as shown, the reading of the ammeter in ampere is
22739_5f30d4e0bccc4fb18970855d479a1358.png
  • 2
  • 3
  • 1
  • 0
An alternating voltage $$V =200\sqrt{2} \sin{100t}$$, Where $$V$$ is in volt and $$t$$ is in seconds, is connected to a series combination of 1$$\mu\text{F}$$ capacitor and $$10\ \text{k}\Omega $$ resistor through an AC ammeter. The reading of the ammeter will be_____
  • $$\sqrt{2}\ \text{mA}$$
  • $$10\sqrt{2}\ \text{mA}$$
  • $$2\ \text{mA}$$
  • 20mA
If alternating current of rms value 'a' flows through resistance R then power loss in resistance is :
  • Zero
  • $$a^2R$$
  • $$\dfrac{a^2R}{2}$$
  • $$2 a^2R$$
The capacitor of an oscillatory circuit of negligible resistance is enclosed in a evacuated container. The frequency of the circuit is 150 kHZ and when the container is filled with a gas, the frequency changes by 100 HZ. The dielectric constant of the gas.
  • 2
  • 1.53
  • 1.0012
  • 3
In the AC circuit shown, $$X_{L}=7\Omega ,R=4\Omega\ and\ X_{c}=4\Omega .$$ The reading of the ideal voltmeter $$V_{2}\ is\ 8\sqrt{2}$$. The reading of the ideal ammeter will be:

71750_e947bf3ff6484af8b8126a19ebad84e6.png
  • $$1A$$
  • $$2A$$
  • $$\sqrt{2}A$$
  • $$\dfrac{1}{\sqrt{2}}A$$
A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be:-
  • $$\frac{f} {4}$$
  • 8f
  • $$\dfrac{f} {2\sqrt{2}}$$
  • $$\frac{f} {2}$$
For a series LCR circuit the power loss at resonance is : -
  • $$\dfrac{V^{2}}{\left [ \omega L-\dfrac{1}{\omega C} \right ]}$$
  • $$I^{2}L\omega $$
  • $$I^{2}R$$
  • $$\dfrac{V^{2}}{C\omega }$$
The natural frequency of the circuit shown in fig. is
120955.png
  • $$\dfrac {1}{\sqrt {LC}}$$
  • $$\dfrac {1}{2\sqrt {LC}}$$
  • $$\dfrac {2}{\sqrt {LC}}$$
  • none of these
The frequency of oscillation of current in the inductor is

77215.png
  • $$\dfrac{1}{3\sqrt{LC}}$$
  • $$\dfrac{1}{6\pi \sqrt{LC}}$$
  • $$\dfrac{1}{\sqrt{LC}}$$
  • $$\dfrac{1}{2\pi \sqrt{LC}}$$
The capacitance in an oscillatory LC circuit is increased by 1%. The change in inductance required to restore its frequency of oscillation is to
  • decrease it by 0.5%
  • increase it by 1%
  • decrease it by 1%
  • decrease it by 2%
An inductor, a resistor and a capacitor are joined in series with an AC source. As the frequency of the source is slightly increased from a very low value, the reactance
  • of the inductor increases
  • of the resistor increases
  • of the capacitor increases
  • of the circuit increases
The circuit shown in Fig. acts as a 
146012_ac22e1264c3a4ab8980d096b17f957b6.png
  • tuned filter
  • low pass filter
  • high pass filter
  • rectifier
A steady potential difference of 100 V produces heat at a constant rate in a resistor. The alternating voltage which will produce half the heating effect in the same resister will be
  • 100 V
  • 50 V
  • 70.7 V
  • 141.4 V
In an $$\text{LCR}$$ circuit the capacitance is made $$\dfrac{1}{4}^{th}$$ then what should be the change in inductance that the circuit remains in resonance again?
  • $$8\ \text{times}$$
  • $$\dfrac{1}{4}\ \text{times}$$
  • $$2\ \text{times}$$
  • $$4\ \text{times}$$

The square root of the product of inductance and capacitance has dimensions of
  • length
  • mass
  • time
  • dimensionless

A $$50\ \text{Hz},\ 20\ \text{V}\ \text{AC}$$ source is connected across $$R$$ series circuit as shown in Figure If the voltage across $$R$$ is $$12\text{V}$$ then voltage across capacitor is


146028.PNG
  • $$8\ \text{V}$$
  • $$16\ \text{V}$$
  • $$10\ \text{V}$$
  • $$\text{cannot be predicted as values of R and C are not given.}$$
A capacitor has capacitance $$0.5nF$$. A choke of $$5\mu H$$ is connected in series. An electromagnetic wave of wavelength $$\lambda$$ is found to resonate with it. Find $$\lambda$$ (in meter).
  • $$10 \pi$$
  • $$20\pi$$
  • $$30 \pi$$
  • $$5\pi$$
In above circuit, what is the potential drop across $$ZY$$?
146232.jpg
  • 160 V
  • $$\displaystyle 80\sqrt{80}$$
  • 80 V
  • zero
When $$4\ V$$ DC is connected across an inductor, current is $$0.2\ A$$. When AC of $$4\ V$$ is applied the current is $$0.1\ A$$. Then self inductance of the coil is:
[Given $$\omega = 1000\  rads^{-1}$$]
  • $$20\ mH$$
  • $$40\ mH$$
  • $$20 \sqrt{3}\ mH$$
  • none of these
A leaky capacitor $$10\ \Omega/ 60^{\circ}$$ is connected in series with a 10 $$\Omega$$ resistance. Find the overall impedance.
146581_bb7609a28eaf4e38b7d76085a9ad7f24.png
  • $$\displaystyle 10\ \Omega$$
  • $$\displaystyle 10 \sqrt 2\ \Omega$$
  • $$\displaystyle 15\ \Omega$$
  • $$\displaystyle 10\sqrt 3\ \Omega$$
If the output is taken across a capacitor in a series RLC circuit then it acts as
146337_b7235c29ed0c4abf9f806419e931da16.png
  • band-pass filter
  • high-pass filter
  • low-pass filter
  • band reject filter
In the given circuit what is the potential drop across resistance?
146228.png
  • 40 V
  • 80 V
  • 120 V
  • zero
$$\displaystyle I = 6\cos  wt + 8\sin wt$$ is applied across a resistor of 40 $$\Omega$$. Find the potential difference across the resistor.
  • 660 V
  • 80 V
  • 330 V
  • 400 V
An inductor $$10 \Omega/60^{\circ}$$ is connected to a $$5 \Omega$$ resistance in series. Find net impedance.
146618.jpg
  • $$15 \Omega$$
  • $$12 \Omega$$
  • $$13.2 \Omega$$
  • $$18 \Omega$$
A capacitor acts as an infinite resistance for
  • $$DC$$
  • $$AC$$
  • $$DC$$ as well as $$AC$$
  • neither $$AC$$ nor $$DC$$
0:0:1


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