JEE Questions for Physics Alternating Current Quiz 5 - MCQExams.com

In a series resonant L-C-R circuit, the voltage across R is 100 V and R =1 kΩ with C = 2µF. The resonant frequency co is 200 rad s-1. At resonance, the voltage across L is
  • 2.5 × 10-2 V
  • 40 V
  • 250 V
  • 4 × 10-3 V
A fully charged capacitor C with initial charge q0 is connected to a coil of self inductance L at t = 0. The time at which the energy is stored equally between the electric and the magnetic fields is

  • Physics-Alternating Current-61608.png
  • 2)
    Physics-Alternating Current-61609.png

  • Physics-Alternating Current-61610.png

  • Physics-Alternating Current-61611.png
At time t = 0, a battery of 10 V is connected across points A and B in the given circuit. If the capacitors have no charge initially, at what time (in sec) does the voltage across them become 4 V? (take, ln 5 =1.6, ln 3 =1.1)
Physics-Alternating Current-61613.png
  • 2
  • 3
  • 2.5
  • 3/2
In the circuit shown below, the key K is closed at t = 0. The current through the battery is
Physics-Alternating Current-61615.png

  • Physics-Alternating Current-61616.png
  • 2)
    Physics-Alternating Current-61617.png

  • Physics-Alternating Current-61618.png

  • Physics-Alternating Current-61619.png
An inductor of 2 H and a resistance of 10Ω are connected in series with a battery of 5 V. The initial rate of change of current is
  • 0.5 As-1
  • 2.0 As-1
  • 2.5 As-1
  • 0.25 As-1
A capacitor of capacity C has reactance X.If capacitance and frequency become double, then reactance will be
  • 4 X
  • X/2
  • X/4
  • 2 X
The time constant of the given circuit is
Physics-Alternating Current-61622.png

  • Physics-Alternating Current-61623.png
  • 2)
    Physics-Alternating Current-61624.png

  • Physics-Alternating Current-61625.png
  • None of these
An inductor (L=100 mH) a resistor (R =100Ω) and a battery (E =100 V) are initially connected in series as shown in the figure. After a long time the battery is disconnected after short circuiting the points A and B. The current in the circuit 1 ms after the short circuit is
Physics-Alternating Current-61627.png
  • (1/e) A
  • e A
  • 0.1 A
  • 1 A

Physics-Alternating Current-61629.png

  • Physics-Alternating Current-61630.png
  • 2)
    Physics-Alternating Current-61631.png

  • Physics-Alternating Current-61632.png

  • Physics-Alternating Current-61633.png
Find the time in which current becomes 81 mA, when the switch S is closed at t= 0.
Physics-Alternating Current-61635.png
  • 5.5 ms
  • 11.65 ms
  • 15 ms
  • 19.6 ms
Current from A to B in the straight wire is decreasing. The direction of induced current in the loop, Fig. is
Physics-Alternating Current-61637.png
  • clockwise
  • anticlockwise
  • changing
  • nothing can be said
The mutual inductance between two coils depends on
  • medium between the coils
  • separation between the two coils
  • orientation of the coils
  • All the above factors
In Fig. maximum deflection in galvanometer G occurs when
Physics-Alternating Current-61638.png
  • magnet is pushed into the coil
  • magnet is rotated into the coil
  • magnet is stationary at the centre of the coil
  • number of turns in the coil is reduced
A coil has an area of 0.05 m2 and has 800 turns. After placing the coil in a magnetic field of strength 4×10-5 Wb/m2, perpendicular to the field, the coil is rotated through 90o in 0.1 s. the average e.m.f. induced is
  • zero
  • 0.016 V
  • 0.01 V
  • 0.032 V
In Fig. final value of current in 30 Ω resistor, when plug of key K is inserted is
Physics-Alternating Current-61640.png
  • 0.1 A
  • 0.2 A
  • 0.3 A
  • zero
A dynamo dissipates 20watt, when it supplies a current of 4 amp. Through it. If the terminal potential difference is 220 volt, the e.m.f produced is
  • 220 volt
  • 225 volt
  • 215 volt
  • 300 volt
A long solenoid of length l, cross section A, having N1 turns has wound about its centre a small coil of N2 turns as shown. Then the mutual inductance of the two circuit is
Physics-Alternating Current-61643.png

  • Physics-Alternating Current-61644.png
  • 2)
    Physics-Alternating Current-61645.png

  • Physics-Alternating Current-61646.png

  • Physics-Alternating Current-61647.png
There are several methods of achieving electric energy such as by electrostatic generator, electro-magnetic generator, battery, thermocouple, photoelectric cells. From the point of view of electric energy, the choices can be arranged as
  • battery, thermocouple, electromagnetic generator, electrostatic generator and others.
  • Electromagnetic generator, electrostatic generator, battery and others
  • Electrostatic generator, battery electro-magnetic generator and others
  • Thermocouple, photo electric cell, battery and others
The current from A to B is increasing in magnitude. What is the direction of induced current, if any, in the loop shown in Fig.
Physics-Alternating Current-61649.png
  • no current is induced
  • clockwise current
  • anti clock wise current
  • alternating current
A copper ring having a cut such as not to form a complete loop is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is
Physics-Alternating Current-61650.png
  • g
  • less than g
  • more than g
  • 0
A square loop of wire of side 5 cm is lying on a horizontal table. An electromagnet above and to one side of the loop is turned on, causing a uniform magnetic field downwards at an angle of 60o to the vertical as shown in fig. The magnetic induction is 0.50 T. The average induced e.m.f in the loop, if the field increases from zero to its final value in 0.2s is
Physics-Alternating Current-61651.png

  • Physics-Alternating Current-61652.png
  • 2)
    Physics-Alternating Current-61653.png
  • 0

  • Physics-Alternating Current-61654.png
Fig. represents two bulbs B1 & B2 resistor R and an inductor L. When the switch S is turned off
Physics-Alternating Current-61656.png
  • both B1 & B2 die out promptly
  • both B1 & B2 die out with some delay
  • B1 dies out promptly but B2 with some delay
  • B2 dies out promptly But B1 with some delay
A conducting ring R is placed on the axis of a barmagnet M. The plane of R is perpendicular to the axis. M can move along this axis.
Physics-Alternating Current-61657.png
  • M will repel R when it is moving towards R
  • M will attract R when it is moving towards R
  • M will repel R when moving towards as well as away from R
  • M will attract R when moving towards as well as away from R
A conducting rod AB moves parallel to X- axis in a uniform magnetic field pointing in the positive Z direction. The ends A and B are charged as
Physics-Alternating Current-61658.png
  • Negative
  • Positive
  • B is +, A is –
  • B is -, A is +
If A and B are identical bulbs, which bulb glows brighter in the circuit shown?
Physics-Alternating Current-61659.png
  • A
  • B
  • both equally bright
  • cannot say

Physics-Alternating Current-61661.png

  • Physics-Alternating Current-61662.png
  • 2)
    Physics-Alternating Current-61663.png

  • Physics-Alternating Current-61664.png

  • Physics-Alternating Current-61665.png
In the circuit shown in fig at resonance:
Physics-Alternating Current-61666.png
  • the power factor is zero
  • the current through the a.c source is minimum
  • the current through the a.c source is maximum
  • currents through L and R are equal
A coil of resistance R and inductance L is connected to a battery of e.m.f E volt. The final current in the coil is

  • Physics-Alternating Current-61667.png
  • 2)
    Physics-Alternating Current-61668.png

  • Physics-Alternating Current-61669.png

  • Physics-Alternating Current-61670.png
An inductance has a high resistance to a.c. and low to d.c. when a d.c. voltage source having some a.c. component superimposed on it sends current through an inductance to load resistance
  • the d.c. voltage falls appreciably across the load and a.c. component falls by only a small amount
  • the a.c. voltage falls appreciably across the load and d.c. voltage falls by only a small amount
  • both a.c. and d.c. voltages fall by the same small percentage
  • both, a.c. and d.c. voltages fall to nearly zero.
A 100 mH coil carries a current of 1 A. Energy stored in magnetic field is
  • 0.05 J
  • 0.5 J
  • 1J
  • 0.1J
The output current versus time curve of a rectifier is shown in Fig. The average value of the output current in this case is
Physics-Alternating Current-61672.png

  • Physics-Alternating Current-61673.png
  • 2)
    Physics-Alternating Current-61674.png

  • Physics-Alternating Current-61675.png

  • Physics-Alternating Current-61676.png
In the a.c. circuit shown in fig. the supply voltage has a constant r.m.s value V, but variable frequency f, Resonance frequency is
Physics-Alternating Current-61677.png
  • 10
  • 100
  • 1000
  • 200
In the circuit shown in fig if value of R = 60Ω, then the current flowing through the condenser will be
Physics-Alternating Current-61679.png
  • 0.5 A
  • 0.25 A
  • 0.75
  • 1.0 A
The value of conductance in the adjoining circuit shown if fig is
Physics-Alternating Current-61681.png
  • 0.1 mho
  • 0.025 mho
  • 0.103 mho
  • 9.7 mho
If number of turns in primary and secondary coils is increased to two times each, the mutual inductance
  • becomes 4 time
  • becomes 2 time
  • becomes 1/4 time
  • remains unchanged
The current flowing in a coil of self inductance 0.4 mH is increased by 250 mA in 0.1 s. The e.m.f induced will be
  • + 1 V
  • -1V
  • +1 mV
  • –1mV
Mutual inductance of two coils can be increased by
  • decreasing the number of turns in the coils
  • increasing the number of turns in the coils
  • winding the coils on wooden cores
  • none of the above
An LCR series circuit is connected to a source of alternating current. At resonance, the applied voltage and the current flowing through the circuit will have a phase difference of
  • π
  • π/2
  • π/4
  • 0
In general, in an alternating current circuit
  • the average value of current is zero
  • the average value of square of current is zero
  • average power dissipation is zero
  • the phase difference between voltage and current is zero
In a noiseless transformer, an alternating current of 2 ampere is flowing in the primary coil. The no. of turns in the primary and secondary coils are 100 and 20 respectively. The value of the current in secondary coil is
  • 0.08 A
  • 0.4 A
  • 5A
  • 10A
In a car spark coil, an emf of 40000 V is induced in a secondary when the primary current changes from 4 A to zero in 10μs. Find the mutual inductance between the primary and secondary windings of the spark coil.
  • 0.6 H
  • 0.4 H
  • 0.2 H
  • 0.1 H
A straight conductor of length 0.4m is moved with a speed of 7ms-1 perpindicular to magnetic field of induction 0.9 Wb/m2. The induced e.m.f across the conductor is
  • 25.2 V
  • 5.04 V
  • 2.52 V
  • 1.26 V
In an A.C. circuit, the current is i = 5 sin (100t - π/amp and the a.c. potential is V = 200 sin (100t) volt. Then, the power consumption is
  • 200 watts
  • 40 watts
  • 1000 watts
  • 0 watts
A metal ring is held horizontally and bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is
  • equal to g
  • less than g
  • more than g
  • depends on the diameter of ring and length of magnet

Physics-Alternating Current-61690.png
  • zero
  • 0.5 V0I0
  • 0.707 V0I0
  • 1.414 V0I0
In the circuit shown in fig what will be the reading of the reading of the voltmeter?
Physics-Alternating Current-61692.png
  • 300 V
  • 900 V
  • 200 V
  • 400 V
In the circuit shown in fig. what will be the readings of voltmeter and ammeter ?
Physics-Alternating Current-61694.png
  • 800 V, 2A
  • 220 V, 2.2 A
  • 300 V, 2A
  • 100 V, 2 A
In a transformer, np = 500, ns= 5000. Input voltage is 20 V and frequency is 50 Hz. Then in the output, we have
  • 200V, 500Hz
  • 200V,50 Hz
  • 20 V,50 Hz
  • 2V, 5 Hz
In an ac circuit, with voltage V and current I the power dissipated is
  • VI
  • 2)
    Physics-Alternating Current-61697.png

  • Physics-Alternating Current-61698.png
  • depends on the phase angle between V and I.
Two coils have mutual inductance 0.005 H. The current changes in the first coil according to equation I = I0 sin ωt where I0 = 10 A and ω = 100 π rad/ sec. The maximum value of e.m.f in second coil is
  • 2π
  • 5π
  • π
  • 4π
0:0:1


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