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CBSE Questions for Class 12 Medical Physics Alternating Current Quiz 8 - MCQExams.com

A resistor R, inductor L and a capacitor C are connected in series to an oscillator of frequency v. If the resonant frequency is vr, then the current lags behind the voltage, when:
  • v=0
  • v<vr
  • v>vr
  • v=vr
In L-C-R circuit, f=50πHz, V=50V, R=300Ω. If L=1H and C=20μC, then the voltage across capacitor is :
  • 50V
  • 20V
  • Zero
  • 30V
A coil of inductive reactance 1/3Ω and resistance 1Ω is connected to 200V, 50Hz A.C. supply. The time lag between maximum voltage and current is
  • 1600s
  • 1200s
  • 1300s
  • 1500s
An inductive coil has a resistance of 100 When an AC signal of frequency 1000 Hz is applied to the coil, the voltage leads the current by 45o. The inductance of the coil is 
  • 110π
  • 120π
  • 140π
  • 160π
An AC source is connected in parallel with an L-C-R circuit as shown. Let IS,IL,IC and IR denote the currents through and VS,VL,VC and VR voltages across the corresponding components. Then :

661326_9c610643e8b34bf7a5ba117c03e31e3e.png
  • IS=IL+IC+IR
  • VS=VL+VC+VR
  • (IL,IC,IR)<IS
  • IL,IC may be greater than IS
At inductance 1 H is connected in series with an AC source of 220 V and 50 Hz. The inductive resistance (in ohm) is :
  • 2π
  • 50π
  • 100π
  • 1000π
In an LCR circuit having L=8H, C=0.5μF and R=100Ω in series, the resonance frequency rad/s is?
  • 600
  • 200
  • 250/π
  • 500
In an LCR series circuit, the values of R,XL and XC are 120Ω,180Ω and 130Ω, what is the impedance of the circuit?
  • 120Ω
  • 130Ω
  • 180Ω
  • 330Ω
A series resonant circuit contains L=5πmH,C=200πμF and R=100μ. If a source of emf e=200sin1000πt is applied, then the rms current is:
  • 2A
  • 2002A
  • 1002A
  • 1.41A
The alternating voltage and current in an electric circuit are respectively given by E=100sin100πt,I=5sin100πt. The reactance of the circuit will be :
  • 1Ω
  • 0.05Ω
  • 20Ω
  • Zero
In non-resonant circuit, what will be the nature of the circuit for frequencies higher than the resonant frequency?
  • Resistive
  • Capacitive
  • Inductive
  • None of these
In a circuit, L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45o. The value of C is :
  • 1πf(2πfL+R)
  • 1πf(2πfLR)
  • 12πf(2πfL+R)
  • 12πf(2πfLR)
A 220V main supply is connected to a resistance of 100kΩ. The effective current is?
  • 2.2mA
  • 2.22mA
  • 2.22mA
  • None of these
Which one of the following curves represents variation of current i with frequency f in series LCR circuit?
For the given circuit, the natural frequency is given by :

681166_6047359d61fb4717b6cd056e95db39ec.png
  • 12πLC
  • 12πLC
  • LC
  • CL
A 44mH inductor is connected to a 220V, 50Hz AC supply. Then, the inductive reactance of the inductor is :
  • 3.82Ω
  • 10.8Hz
  • 13.82Ω
  • 21.5Hz
In the given circuit R in pure resistance and X is unknown circuit element. An AC voltage source is applied across A and C. If VAB=VAC, then X is
683231_543dbbd9f61c4dd686d73f34aacb1c14.PNG
  • Pure resistance
  • Pure inductance
  • Combination of inductance and capacitance at resonance
  • None of the above
The frequency of the output signal becomes ________ times by doubling the value of the capacitance in the LC oscillator circuit.
  • 2
  • 12
  • 12
  • 2
In a series resonant circuit, the AC voltage across resistance R, inductor L and capacitor C are 5 V, 10 V and 10 V respectively. The AC voltage applied to the circuit will be 
  • 10 V
  • 25 V
  • 5 V
  • 20 V
The power loss in an AC circuit can be minimized by.
  • Decreasing resistance and increasing inductance
  • Decreasing inductance and increasimg resistance
  • Increasing both inductance and resistance
  • Decreasing both inductance and resistance
The diagram given show the variation of voltage and current in an AC circuit. The circuit contains
683040_d460ab95eeb741f1af29dd5b4968371f.png
  • Only a resistor
  • Only a pure inductor
  • Only a capcacitor
  • A capacitor and and inductor
What is the range of the characteristic impedance of a coaxial cable?
  • Between 150Ω to 600Ω
  • Between 50Ω to 70Ω
  • Between 0Ω to 50Ω
  • Between 100Ω to 150Ω
In the given circuit the potential difference across resistance is 54V and power consumed by it is 16W. If AC frequency is 60 Hz find the value of L.
1100814_00be705c1b734a7f871c718b6bfca4e9.png
  • 1H
  • 2H
  • 5H
  • 4H
Consider the RLC circuit given below. The circuit is driven by a 50 Hz AC source with peak voltage 220 V. If R=400Ω,C=200μF and L=6H, the maximum current in the circuit is closest to

739647_84d12ba91d454a0b983c1adf9c509303.png
  • 0.120 A
  • 0.55 A
  • 1.2 A
  • 5.5 A
Consider two series resonant circuits with components L1C1 and L2C2 with same resonant frequency , ω.When connected in series, the resonant frequency of the combination is 
  • 2ω
  • ω2
  • 3ω
  • ω
In the circuit shown in the figure, neglecting source resistance, the voltmeter and ammeter readings will respectively be 
697266_f305177d4d0949c09b2fc2f84d201c46.png
  • 0 V, 8 A
  • 150 V, A 8
  • 150 V, 3 A
  • 0 V, 3 A
A 5cm long solenoid having 10 ohm resistance and 5mH inductance is joined to a 10V battery. At steady state, the current through the solenoid (in ampere) will be
  • 5
  • 2
  • 1
  • zero
Consider L,C,R circuit as shown in figure, with a.c. source of peak value V and angular frequency ω. Then the peak value of current through the ac source.
786198_5429a99f3e2547c487329d4d42bb785a.jpg
  • V1R2+(ωL1ωC)2
  • V1R2+(ωC1ωL)2
  • VR2+(ωL1ωC)2
  • VRωCω2C2+R(ω2C21)2
Statement 1 : An inductance and a resistance are connected in series with an ac circuit. In this circuit the current and the potential difference across the resistance lags behind potential difference across the inductance by an angle of π/2.
Statement 2 : In a LR circuit voltage leads the current by phase angle which depends on the value of inductance and resistance both.
  • Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1.
  • Both statements 1 and 2 are true but statement 2 is not the correct explanation of statement 1.
  • Statement 1 is true but statement 2 is false.
  • Both statements 1 and 2 are false.
In A.C circuit having only capacitor, the current _____
  • lags behind the voltage by π2 in phase
  • leads the voltage by π2 in phase
  • leads the voltage by π in phase
  • lags behind the voltage by π in phase
In the case of an inductor
  • voltage lags the current by π2.
  • voltage leads the current by π2.
  • voltage leads the current by π3.
  • voltage leads the current by π4.
Two coils have mutual inductance 0.005H. The current changes in the first coil according to equation I=I0sinωt, where I0=10A and ω=100πrads1. The maximum value of emf in the second coil is
  • 5
  • 5π
  • 0.5π
  • π
Which of the following graphs represents the correct variation of inductive reactane XL with frequency υ?
An ideal inductor is in turn put across 220V,50Hz and 220V,100Hz supplies. The current flowing through it in the two cases will be then
  • equal
  • different
  • zero
  • infinite
The reciprocal of the impedance of an electric current is?
  • Admittance
  • Susceptance
  • Conductance
  • Reactance
A capacitor 'C' is connected across a D.C. source, the reactance of capacitor will be _________.
  • ZERO
  • HIGH
  • LOW
  • INFINITE
A 5 μF capacitor is connected to a 200 V, 100 Hz ac source. The capacitive reactance is:
  • 212Ω
  • 312Ω
  • 318Ω
  • 412Ω
Which of the following graphs represents the correct variation of capacitive reactance XC with frequency ν?
An inductor of 30 mH is connected to a 220 V, 100 Hz ac source. The inductive reactance is then
  • 10.58Ω
  • 12.64Ω
  • 18.85Ω
  • 22.67Ω
In a series LCR circuit, the plot of Im vs ω is shown in the figure. The bandwidth of this plot will be then
943669_a46d321e465f4a0abc837a41fd28f062.png
  • Zero
  • 0.1rads1
  • 0.2rads1
  • 0.4rads1
In the series LCR circuit shown the impedance is:
943609_7b796d403da24c4b8849b252abb84214.png
  • 200Ω
  • 100Ω
  • 300Ω
  • 500Ω
In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?
  • Only resistor
  • Resistor and inductor
  • Resistor and capacitor
  • Only a capacitor
Phase difference between voltage and current in a capacitor in an ac circuit is then
  • π
  • π/2
  • 0
  • π/3
A circuit containing a 20 Ω resistor and 0.1μF capacitor in series is connected to 230 V AC supply of angular frequency 100 rad s1. The impedance of the circuit is
  • 105Ω
  • 104Ω
  • 106Ω
  • 1010Ω
A sinusoidal voltage of peak value 293 V and frequency 50 Hz is applied to a series LCR circuit in which R = 6 Ω, L = 25 mH and C = 750 μF. The impedance of the circuit is:
  • 7.0 Ω
  • 8.9 Ω
  • 9.9 Ω
  • 10.0 Ω
The resonant frequency of a series LCR circuit with L = 2.0H,C=32μF and R= 10 Ω is
  • 20Hz
  • 30Hz
  • 40Hz
  • 50Hz
A 0.2 Ω resistor and 15 μF capacitor are connected in series to a 220 V, 50 Hz ac source. The impedance of the circuit is
  • 250Ω
  • 268Ω
  • 29.15Ω
  • 291.5Ω
A coil of inductance L=300mH and resistance R=140mΩ is connected to a constant voltage source, Current in the coil will reach to 50 of its steady state value after t is nearly equal to:
  • 15s
  • 0.75s
  • 0.15s
  • 1.5s
In a series resonant R-L-C circuit, if L is increased by 25%  and C is decreased by 20% , then the resonant frequency will
  • Increases by 10% 
  • Decreases by 10% 
  • Remain unchanged
  • Increases by 2.5% 
A series resonant LCR circuit has a quality factor (Q-factor) = 0.If R 2 kΩ, C = 0.1 μF, then the value of Inductance is
  • 0.1 H
  • 0.064 H
  • 2 H
  • 5 H
0:0:1


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