JEE Questions for Physics Alternating Current Quiz 10 - MCQExams.com

A resistance R, inductance L and capacitor C are connected in series to an oscillator of frequency f. If resonant frequency is frthen current will lag thevoltage when
  • f = 0
  • f < fr
  • f = fr
  • f > fr
The reading of ammeter in the circuit shown will be
Physics-Alternating Current-62174.png
  • 2 A
  • 2.4 A
  • Zero
  • 1.7 A
An ac source of angular frequency ω is fed across aresistor r and a capacitor C in series. The currentregistered is I. If the frequency of source is changed to ω /3 (maintaining the same voltage), the current in thecircuit is found to be halved. Calculate the ratio ofreactance to resistance at the original frequency ω

  • Physics-Alternating Current-62176.png
  • 2)
    Physics-Alternating Current-62177.png

  • Physics-Alternating Current-62178.png

  • Physics-Alternating Current-62179.png
Is it possible
Physics-Alternating Current-62181.png
  • Yes
  • No
  • Cannot be predicted
  • Insufficient data to reply
In the adjoining ac circuit the voltmeter whose readingwill be zero at resonance is
Physics-Alternating Current-62188.png
  • V1
  • V2
  • V3
  • V4
In the inductive circuit given in the figure, the current rises after the switch is closed. At instant when thecurrent is 15 mA, then potential difference across theinductor will be
Physics-Alternating Current-62189.png
  • Zero
  • 240 V
  • 180 V
  • 60 V
Which one of the following curves represents the variation of impedance (Z) with frequency f in series LCR circuit

  • Physics-Alternating Current-62191.png
  • 2)
    Physics-Alternating Current-62192.png

  • Physics-Alternating Current-62193.png

  • Physics-Alternating Current-62194.png
The variation of the instantaneous current (I) and the instantaneous e.m.f. (E) in a circuit is as shown in fig. Which of the following statement is correct?
Physics-Alternating Current-62196.png
  • The voltage lags behind the current by π /2
  • The voltage leads the current by π/2
  • The voltage and the current are in phase
  • The voltage leads the current by π
The figure shows variation of R, XL and XC with frequency f in a series L, C, R circuit. Then for what frequency point, the circuit is inductive
Physics-Alternating Current-62198.png
  • A
  • B
  • C
  • All points
An alternating e.m.f. is applied across a parallel combination of a resistance R, capacitance C and an inductance L. If IR, IL, ICare the currents through R, L and C respectively, then the diagram which correctly represents the phase relationship among IR, IL, ICand source e.m.f. E, is given by

  • Physics-Alternating Current-62200.png
  • 2)
    Physics-Alternating Current-62201.png

  • Physics-Alternating Current-62202.png

  • Physics-Alternating Current-62203.png
An ac source of variable frequency f is connected to an LCR series circuit. Which of the graphs in figure represents the variation of current I in the circuit with frequency f

  • Physics-Alternating Current-62205.png
  • 2)
    Physics-Alternating Current-62206.png

  • Physics-Alternating Current-62207.png

  • Physics-Alternating Current-62208.png
The r.m.s. voltage of the wave form shown is
Physics-Alternating Current-62210.png
  • 10 V
  • 7 V
  • 6.37 V
  • None of these
A constant voltage at difference frequencies is applied across a capacitance C as shown in the figure. Which of the following graphs correctly depicts the variation of current with frequency
Physics-Alternating Current-62212.png

  • Physics-Alternating Current-62213.png
  • 2)
    Physics-Alternating Current-62214.png

  • Physics-Alternating Current-62215.png

  • Physics-Alternating Current-62216.png
The output current versus time curve of a rectifier is shown in the figure. The average value of output current in this case is
Physics-Alternating Current-62218.png
  • 0
  • 2)
    Physics-Alternating Current-62219.png

  • Physics-Alternating Current-62220.png

  • Physics-Alternating Current-62221.png
The current \'i\' in an inductance coil varies with time \'t\' according to following graph
Which of the following plots shows the variation of voltage in the coil
Physics-Alternating Current-62223.png

  • Physics-Alternating Current-62224.png
  • 2)
    Physics-Alternating Current-62225.png

  • Physics-Alternating Current-62226.png

  • Physics-Alternating Current-62227.png
Two sinusoidal voltages of the same frequency are shown in the diagram. What is the frequency, and the phase relationship between the voltages
Physics-Alternating Current-62229.png
  • (a)
  • (b)
  • (c)
  • (d)
The voltage across a pure inductor is represented by thefollowing diagram. Which of the following diagramswill represent the current
Physics-Alternating Current-62231.png

  • Physics-Alternating Current-62232.png
  • 2)
    Physics-Alternating Current-62233.png

  • Physics-Alternating Current-62234.png

  • Physics-Alternating Current-62235.png
In pure inductive circuit, the curves between frequency f and reciprocal of inductive reactance 1 /XL is

  • Physics-Alternating Current-62236.png
  • 2)
    Physics-Alternating Current-62237.png

  • Physics-Alternating Current-62238.png

  • Physics-Alternating Current-62239.png
The current i in the circuit shown here varies with time t is
Physics-Alternating Current-62241.png

  • Physics-Alternating Current-62242.png
  • 2)
    Physics-Alternating Current-62243.png

  • Physics-Alternating Current-62244.png

  • Physics-Alternating Current-62245.png
The resonance point in XL – f and XC – f curves is
Physics-Alternating Current-62246.png
  • P
  • Q
  • R
  • S
The i – v curve for anti-resonant circuit is

  • Physics-Alternating Current-62248.png
  • 2)
    Physics-Alternating Current-62249.png

  • Physics-Alternating Current-62250.png

  • Physics-Alternating Current-62251.png
The graphs given below depict the dependence of two reactive impedances X1 and X2on the frequency of the alternating e.m.f. applied individually to them. We can then say that
Physics-Alternating Current-62252.png
  • X1 is an inductor and X2 is a capacitor
  • X1 is a resistor and X2 is a capacitor
  • X1 is a capacitor and X2 is an inductor
  • X1 is an inductor and X2 is a resistor
Which of the following plots may represent the reactance of a series LC combination
Physics-Alternating Current-62254.png
  • a
  • b
  • c
  • d
Which of the following curves correctly represents the variation of capacitive reactance XC with frequency f

  • Physics-Alternating Current-62256.png
  • 2)
    Physics-Alternating Current-62257.png

  • Physics-Alternating Current-62258.png

  • Physics-Alternating Current-62259.png
The r.m.s. value of potential difference V shown in the figure is
Physics-Alternating Current-62261.png

  • Physics-Alternating Current-62262.png
  • 2)
    Physics-Alternating Current-62263.png

  • Physics-Alternating Current-62264.png

  • Physics-Alternating Current-62265.png
Assertion In series LCR circuit resonance can take place.
Reason Resonance takes place if inductance and capacitive reactances are equal and opposite.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion The alternating current lags behind the e.m.f. by a phase angle of π/2, when ac flows through an inductor.
Reason The inductive reactance increases as the frequency of ac source decreases.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion Capacitor serves as a block for dc and offers an easy path to ac.
Reason Capacitive reactance is inversely proportional to frequency.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion When capacitive reactance is smaller than the inductive reactance in LCR circuit, e.m.f. leads the current.
Reason The phase angle is the angle between the alternating e.m.f. and alternating current of the circuit.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion A capacitor of suitable capacitance can be used in an ac circuit in place of the choke coil.
Reason A capacitor blocks dc and allows ac only.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion : If the frequency of alternating current in an ac circuit consisting of an inductance coil is increased, then current gets decreased.
Reason The current is inversely proportional to frequency of alternating current.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion 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 π/2.
Reason In LR circuit voltage leads the current by phase angle which depends on the value of inductance and resistance both.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion An alternating current does not show any magnetic effect.
Reason Alternating current varies with time.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion The dc and ac both can be measured by a hot wire instrument.
Reason The hot wire instrument is based on the principle of magnetic effect of current.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion ac is more dangerous than dc.
Reason Frequency of ac is dangerous for human body.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion Average value of ac over a complete cycle is always zero.
Reason Average value of ac is always defined over half cycle.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion The divisions are equally marked on the scale of ac ammeter.
Reason Heat produced is directly proportional to the current.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion For an electric lamp connected in series with a variable capacitor and ac source, its brightness increases with increase in capacitance.
Reason Capacitive reactance decreases with increase in capacitance of capacitor.
  • 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 Reason is not the correct explanation of the Assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
What is the r.m.s. value of an alternating current which when passed through a resistor prodcues heat which is thrice of that produced by a direct current of 2 amperes in the same resistor
  • 2 amp
  • 3.46 amp
  • 6 amp
  • 0.66 amp

Physics-Alternating Current-62279.png
  • 0.6, 0.06 W
  • 0.06, 0.6 W
  • 0.6, 4.8 W
  • 4.8, 0.6 W
In an LCR circuit R = 100 ohm. when capacitance C is removed, the current lags behind the voltage by π/3. When inductance L is removed, the current leads the voltage by π/3. The impedance of the circuit is
  • 50 ohm
  • 100 ohm
  • 200 ohm
  • 400 ohm
A group of electric lamps having a total power rating of 1000 watt is supplied by an ac voltage E = 200 sin(310t + 60° ). Then the r.m.s. value o the circuit current is
  • 10A
  • 10√2 A
  • 20 A
  • 20√2 A
Following figure shows an ac generator connected to a \ block box\ through a pair of terminals. The box contains possible R, L, C or their combination, whose elements and arrangements are not known to us. Measurements outside the box reveals that
e = 75 sin (sin ωt) volts,
i = 1.5 sin (ωt + 45° )
amp. The wrong statement is

Physics-Alternating Current-62284.png
  • There must be a capacitor in the box
  • There must be an inductor in the box
  • There must be a resistance in the box
  • The power factor is 0.707
The instantaneous values of current and voltage in an ac circuit are i = 100 sin 314 t amp and e = 200 sin (314 t + π/V respectively. If the resistance is 1 Ω, then the reactance of the circuit will be

  • Physics-Alternating Current-62286.png
  • 2)
    Physics-Alternating Current-62287.png

  • Physics-Alternating Current-62288.png

  • Physics-Alternating Current-62289.png
What will be the self inductance of a coil, to be connected in a series with a resistance of π√3 Ω, such that the phase difference between the e.m.f. and the current at 50 Hz frequency is 30°
  • 0.5 henry
  • 0.03 henry
  • 0.05 henry
  • 0.01 henry

Physics-Alternating Current-62293.png
  • –π/6 rad
  • – π/3 rad
  • π/6 rad
  • π/3 rad
If A and B are identical bulbs, which bulb glows brighter
Physics-Alternating Current-62295.png
  • A
  • B
  • Both equally bright
  • Cannot say
In the circuit shown here, the point C is kept connected to the point A till the current flowing through the circuit becomes constant. Afterward, suddenly point C is disconnected form point A and connected to point B at time t = Q Ratio of the voltage across resistance and the inductor at t = L/R will be equal to
Physics-Alternating Current-62297.png

  • Physics-Alternating Current-62298.png
  • 1
  • –1

  • Physics-Alternating Current-62299.png
Two different coils have self-inductance L1 = 8 mH and L2 = 2 mH The current in one coil is increased at a constant rate. The current in the second coil is also increased at the same rate. At a certain instant of time, the power given to the two coils is the same. At that time the current, the induced voltage and the energy stored in the first coil are i1 , V1 and W1 respectively. Corresponding values for the second coil at the same instant are i2, V2 and W2 respectively. Then,
  • W2 / W1 = 8
  • W2 / W1 = 1/8
  • W2 / W1 = 4
  • W2 / W1 = 1/4

Physics-Alternating Current-62302.png
  • zero
  • 5625 W
  • 150 W
  • 106 W
0:0:1


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