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CBSE Questions for Class 12 Medical Physics Alternating Current Quiz 2 - MCQExams.com

The source frequency for which a 5μ F capacitor has a reactance of 1000Ω is
  • 100π Hz
  • 1000π Hz
  • 200 Hz
  • 5000 Hz
The inductive reactance of a coil is 2500 Ω . On increasing it’s self-inductance to three times, the new inductive reactance will be:


  • 7500Ω
  • 2500Ω
  • 1225Ω
  • zero
In an LCR series circuit, the rms voltages across R, L and C are found to be 10 V, 10 V and 20 V respectively. The rms voltage across the entire combination is
  • 30 V
  • 1μF
  • 20V
  • 102V
In the circuit shown, a 30 V d.c source gives a current 2.0A as recorded in the ammeter A and 30V a.c. source of frequency 100Hz gives a current 1.2A. The inductive reactance is 
22689.png
  • 10ohm
  • 20 ohm
  • 534 ohm
  • 40 ohm
If the values of inductance and frequency in an AC circuit are 2 henry and 1032π Hz respectively then the value of inductive reactance will be
  • 2×103πΩ
  • 2×102Ω
  • 103Ω
  • 2×103Ω
In an oscillating system, a restoring force is a must. In an L-C circuit, the restoring force is provided by a/an
  • inductor
  • capacitor
  • resistor
  • both A and B
The phase difference between the applied emf and the line current in an anti resonant circuit at resonance is
  • π2 radian
  • π radian
  • 3π2 radian
  • zero
The unit of susceptance is
  • ohm
  • ohm1
  • ohm/cm
  • ohm/m
The phase difference between alternating emf and current in a purely capacitive circuit will be
  • zero
  • π
  • π2
  • π2
The reactance of a circuit is zero. It is possible that the circuit contains 
  • an inductor and a capacitor
  • an inductor but no capacitor
  • a capacitor but no inductor
  • neither an inductor nor a capacitor
The resonant frequency in an anti resonant circuit is :
  • 12πLC
  • 12π1LCR2L2
  • 12πLC
  • 12πCL
In an A.C. circuit, the potential difference across an inductance and a resistance joined in series are respectively 16V and 20V. The total potential difference across the circuit is
  • 20.0V
  • 25.6V
  • 31.4V
  • 53.5V
An LCR series circuit contains L=8H, C=0.5 μ F and R = 100Ω .The resonant frequency of the circuit is
  • 100πHz
  • 500πHz
  • 250πHz
  • 125πHz
.In the given circuit, the phase difference between voltages across R and C is 

22697.png
  • zero
  • π/2
  • π
  • 3π/2
An experimentalist has a coil of 3 mH. He wants to make a circuit whose frequency is 106 Hz. The capacity of condenser used will be
  • 752.22μF
  • 852.22μF
  • 950.22μF
  • zero
The correct curve between inductive reactance (XL) and frequency (f) is
When the values of inductance and capacitance in an LC circuit are 0.5 H and 8 μF respectively then current in the circuit is maximum. The angular frequency of alternating e.m.f. applied in the circuit will be
  • 5×103 Radian/sec
  • 50 Radian/sec
  • 5×102 Radian/sec
  • 5 Radian/sec
The inductive reactance of a coil is 2500 Ω. On increasing its self-inductance three times, the new inductive reactance will be
  • 7500 Ω
  • 2500 Ω
  • 1225 Ω
  • zero
The inductive reactance of a choke coil of 1/4π mH in an AC circuit of 50 Hz,  will be
  • 25 ohm
  • 0.25 ohm
  • 0.025 ohm
  • 2.5 ohm
The value of alternating emf in the following circuit will be
148174_542d64131566473aa01f1e9c0df8eb98.png
  • 220 volt
  • 140 volt
  • 20 volt
  • 100 volt
The correct curve between the resistance of a conductor (R) and frequency (f) is
The capacitive reactance at 1600 Hz  is  81 Ω. When the frequency is doubled then capacitive reactance will be
  • 40.5 Ω
  • 81 Ω
  • 162 Ω
  • Zero
An RC circuit is as shown in the following diagram.The capacity reactance and impedance will be
148173.jpg
  • zero
  • infinity
  • 1ωc
  • ωc
The self inductance of a coil is 1/2 henry. At what frequency will its inductive reactance be 3140Ω
  • 100Hz
  • 10Hz
  • 1000Hz
  • 10000Hz
An alternating voltage frequency ω is induced in electric circuit consisting of an inductance L and capacitance C, connected in parallel. Then across the inductance coil the
(i) current is maximum when ω2=1/(LC)
(ii) current is minimum when ω2=1/(LC)
(iii) voltage is minimum when ω2=1/(LC)
(iv) voltage is maximum when ω2=1/(LC)
  • (i) and (iii) are correct
  • (i) and (iv) are correct
  • (ii) and (iii) are correct
  • (ii) and (iv) are correct
Of the following about capacitive reactance which is correct?
  • The reactance of the capacitor is directly proportional to its ability to store charge
  • Capacitive reactance is inversely proportional to the frequency of the current
  • Capacitive reactance is measured in farad
  • The reactance of a capacitor in an AC circuit is similar to the resistance of a capacitor in a DC circuit
The capacitive reactance in an AC circuit is
  • effective resistance due to capacity
  • effective wattage
  • effective voltage
  • None of these
If the inductance of a coil in 1 henry then its effective resistance in a D.C circuit will be
  • zero
  • 1 Ω
  • 2 Ω
The power loss in an AC circuit is Erms Irms, when in the circuit there is only
  • C
  • L
  • R
  • L, C and R
With increase in frequency of an A.C. supply, the inductive reactance
  • decreases
  • increases directly with frequency
  • increases as square of frequency
  • decreases inversely with frequency
The impedance of the tweeter and woofer branches are respectively
149793.png
  • R2+X2C,R2+X2L
  • R2+X2L,R2+X2C
  • R2+(XLXC)2 each
  • (1R2+(1XC1XL)2)1 each
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
  • resistor increases
  • capacitor increases
  • circuit increases
With increase in frequency of an AC supply, the impedence of an L-C-R series circuit
  • remains constant
  • increases
  • decreases
  • decreases at first, becomes minimum and then increases
If a current I given by I=I0sin(ωtπ/2) flows in inductance in an AC circuit which an A.C potential E=E0sinωt has been applied, then power consumption P in the circuit will be
  • P=E0I0/2
  • P=EI/2
  • P=E0I0/2
  • zero
In a series combination of R,L and C to an A.C source at resonance. If R=20 ohm, then impedence Z of the combination is
  • 20 ohm
  • Zero
  • 1 ohm
  • 400 ohm
In an AC circuit, a resistance of R ohm is connected in series with an inductance L. If phase angle between voltage and current be 45o, the value of inductive reactance will be
  • R/4
  • R/2
  • R
  • cannot be found with given the data
An inductance of negligible resistance whose reactance is 22Ω at 200Hz is connected to 200volt. If the line frequency is known to be 50 cycles/second, the equation for the line voltage is :
  • 0.0175 Henry
  • 0.175 Henry
  • 1.75 Henry
  • 17.5 Henry
In series combination of R,L,C with an A.C source at resonanace, if R=20 ohm, then impedence Z of the combination is
  • 20 ohm
  • zero
  • 10 ohm
  • 400 ohm
Resonance frequency of LCR series a.c. circuit is {f}_{0}. Now the capacitance is made 4 times, then the new resonance frequency will become
  • {f}_{0}/4
  • 2{f}_{0}
  • {f}_{0}
  • {f}_{0}/2
For the circuit shown in the fig., the current through the inductor is 0.9A while the current through the condenser is 0.4A. Then
206653.PNG
  • current drawn from generator I=1.13 A
  • \omega=1/(1.5LC)
  • I=0.5A
  • I=0.6A
In a pure capacitive A.C circuit current and voltage differ in phase by
  • {0}^{o}
  • {45}^{o}
  • {90}^{o}
  • {180}^{o}
In a RLC circuit capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the inductance should be changed from L to
  • 4L
  • 2L
  • L/2
  • L/4
If the frequency of an A.C is made 4 times of its initial value, the inductive reactance will
  • be 4 times
  • be 2 times
  • be half
  • remain the same
In series L-C-R circuit, the voltages across R, L and C are {V}_{R}, {V}_{L} and {V}_{C} respectively. Then the voltage of applied a.c. source must be
  • {V}_{R}+{V}_{L}+{V}_{C}
  • \sqrt { { [\left( { V }_{ R } \right) }^{ 2 }+{ \left( { V }_{ L }-{ V }_{ C } \right) }^{ 2 }] }
  • {V}_{R}+{V}_{C}-{V}_{L}
  • { \left[ { \left( { V }_{ R }-{ V }_{ L } \right) }^{ 2 }+{ \left( { V }_{ C } \right) }^{ 2 } \right] }^{ 1/2 }
In a circuit, the current lags behind the voltage by a phase difference of \displaystyle { \pi  }/{ 2 }, the circuit will contain which of the following: 
  • Only R
  • Only C
  • R and C
  • Only L
An A.C. circuit containing only capacitance, the current :
  • Lags the voltage by \displaystyle { 90 }^{ o }
  • Leads the voltage by \displaystyle { 90 }^{ o }
  • Remains in phase with voltage
  • Lags the voltage by \displaystyle { 180 }^{ o }
Assertion: The resistance offered by an inductor in a d.c circuit is always constant.
Reason : The resistance of inductor in steady state is non-zero. 
  • If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
  • If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
  • If Assertion is true statement but Reason is false.
  • If both Assertion and Reason are false statements.
The self inductance of the motor of an electric fan is 10 H. In order to impart maximum powr of 50 Hz, it should be connected to a capacitance of
  • 8\mu F
  • 4\mu F
  • 2\mu F
  • 1\mu F
In a purely inductive circuit, the current:
  • is in phase with the voltage
  • is out of phase with the voltage
  • leads the voltage by \pi / 2
  • lags behind the voltage by \pi /2
Inductive reactance of a coil is expressed in
  • Amphere
  • Ohm
  • Volt
  • Weber
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