CUET Physics MCQs Unit IV Electromagnetic Induction and Alternating Currents

CUET Physics Electromagnetic Induction MCQs

Question: A coil is wound on a frame of rectangular cross-section. If all the linear dimensions of the frame are increased by a factor 2 and the number of turns per unit length of the coil remains the same, self-inductance of the coil increases by a factor of
(a) 4
(b) 8
(c) 12
(d) 16

Answer: B

Question: Choke coil works on the principle of
(a) transient current 
(b) self-induction
(c) mutual induction
(d) wattless current

Answer: B

Question: Whenever the magnetic flux linked with an electric circuit changes, an emf is induced in the circuit. This is called
(a) electromagnetic induction
(b) lenz’s law
(c) hysteresis loss
(d) kirchhoff’s laws

Answer: A

Question: An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e.m.f. is independent of
(a) the strength of the magnet
(b) number of turns of coil
(c) the resistivity of the wire of the coil
(d) speed with which the magnet is moved

Answer: C

Question: A magnet is moved towards a coil (i) quickly (ii) slowly, then the induced e.m.f. is
(a) larger in case (i)
(b) smaller in case (i)
(c) equal to both the cases
(d) larger or smaller depending upon the radius of the coil

Answer: A

Question: In electromagnetic induction, the induced charge is independent of
(a) change of flux
(b) time.
(c) resistance of the coil
(d) None of these

Answer: B

Question: A coil of insulated wire is connected to a battery. If it is connected to galvanometer, its pointer is deflected, because
(a) induced current is set up
(b) no induced current is set up
(c) the coil behaves as a magnet
(d) the number of turns is changed

Answer: A

Question: When current i passes through an inductor of self inductance L, energy stored in it is 1/2. L i2. This is stored in the
(a) current
(b) voltage
(c) magnetic field
(d) electric field

Answer: C

Question: The SI unit of inductance, the henry can be written as
(a) weber/ampere
(b) volt second/ampere
(c) joule/ampere2
(d) all of the above

Answer: D

Question: Two coils, A and B, are lined such that emf ε is induced in B when the current in A is changing at the rate I. If current i is now made to flow in B, the flux linked with A will be
(a) (ε /I)i
(b) εi I
(c) (ε I)i
(d) i I/ε

Answer: A

Question: Two pure inductors each of self inductance L are connected in series, the net inductance is
(a) L
(b) 2 L
(c) L/2
(d) L/4

Answer: B

Question: Henry is the S.I. unit of
(a) resistance
(b) capacity
(c) inductance
(d) current

Answer: C

Question: Eddy currents are produced when
(a) A metal is kept in varying magnetic field
(b) A metal is kept in the steady magnetic field
(c) A circular coil is placed in a magnetic field
(d) Through a circular coil, current is passed

Answer: A

Question: Which of the following is not the application of eddy currents?
(a) Induction furnace
(b) Dead beat galvanometer
(c) speedometer
(d) X-ray crystallography

Answer: D

Question: When the current in a coil changes from 2 amp. to 4 amp. in 0.05 sec., an e.m.f. of 8 volt is induced in the coil. The coefficient of self inductance of the coil is
(a) 0.1 henry
(b) 0.2 henry
(c) 0.4 henr
(d) 0.8 henry

Answer: B

Question: The coefficient of self inductance of a solenoid is 0.18 mH. If a core of soft iron of relative permeability 900 is inserted, then the coefficient of self inductance will become nearly
(a) 5.4 mH
(b) 162 mH
(c) 0.006 mH
(d) 0.0002 mH

Answer: B

Question: The two rails of a railway track, insulated from each other and the ground, are connected to millivoltmeter. What is the reading of the millivoltmeter when a train passes at a speed of 180 km/hr along the track, given that the vertical component of earth’s magnetic field is 0.2 × 10–4 wb/m2 and rails are separated by 1 metre
(a) 10–2 volt
(b) 10 mV
(c) 1 volt
(d) 1 mV

Answer: D

Question: Lenz’s law is a consequence of the law of conservation of
(a) charge
(b) mass
(c) energy
(d) momentum

Answer: C

Question: When current i passes through an inductor of self inductance L, energy stored in it is 1/2. L i2. This is stored in the
(a) current
(b) voltage
(c) magnetic field
(d) electric field

Answer: C

Question: Eddy currents are produced when
(a) A metal is kept in varying magnetic field
(b) A metal is kept in the steady magnetic field
(c) A circular coil is placed in a magnetic field
(d) Through a circular coil, current is passed

Answer: A

Question: A coil of insulated wire is connected to a battery. If it is taken to galvanometer, its pointer is deflected, because
(a) the induced current is produced
(b) the coil acts like a magnet
(c) the number of turns in the coil of the galvanometer are changed
(d) None of these

Answer: A

Question: If a coil made of conducting wires is rotated between poles pieces of the permanent magnet. The motion will generate a current and this device is called
(a) An electric motor
(b) An electric generator
(c) An electromagnet
(d) All of the above

Answer: B

Question: A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. An e.m.f. is induced in the loop, if 
(a) it is translated.
(b) it is rotated about its axis.
(c) both (a) and (b).
(d) it is rotated about its diameter.

Answer: D

Question: Whenever, current is changed in a coil, an induced e.m.f. is produced in the same coil. This property of the coil is due to
(a) mutual induction
(b) self induction
(c) eddy currents
(d) hysteresis

Answer: B

Question: The mutual inductance between two coils depends on
(a) medium between the coils
(b) separation between the two coils
(c) orientation of the two coils
(d) All of the above

Answer: D

Question: The polarity of induced emf is given by
(a) Ampere's circuital law
(b) Biot-Savart law
(c) Lenz’s law
(d) Fleming's right hand rule

Answer: C

Question: A dynamo converts
(a) mechanical energy into thermal energy
(b) electrical energy into thermal energy
(c) thermal energy into electrical energy
(d) mechanical energy into electrical energy
(e) electrical energy into mechanical energy

Answer: D

Question: The self inductance associated with a coil is independent of
(a) current
(b) time
(c) induced voltage
(d) resistance of coil

Answer: D

Question: The plane in which eddy currents are produced in a conductor is inclined to the plane of the magnetic field at an angle equal to
(a) 45°
(b) 0°
(c) 180°
(d) 90°

Answer: D

Question: Two coils of self inductances 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is
(a) 6 mH
(b) 4 mH
(c) 16 mH
(d) 10 mH

Answer: B

Question: A generator has an e.m.f. of 440 Volt and internal resistance of 4000 hm. Its terminals are connected to a load of 4000 ohm. The voltage across the load is
(a) 220 volt
(b) 440 volt
(c) 200 volt
(d) 400 volt

Answer: B

Question: A current carrying infinitely long wire is kept along the diameter of a circular wire loop, without touching it, the correct statement(s) is(are)
I. The emf induced in the loop is zero if the current is constant.
II. The emf induced in the loop is finite if the current is constant.
III. The emf induced in the loop is zero if the current decreases at a steady rate
(a) I only
(b) II only
(c) I and II
(d) I, II and III

Answer: A

Question: The plane in which eddy currents are produced in a conductor is inclined to the plane of the magnetic field at an angle equal to

(a) 45°
(b) 0°
(c) 180°
(d) 90°

Answer: D

Question: Lenz’s law is a consequence of the law of conservation of
(a) charge
(b) mass
(c) energy
(d) momentum

Answer: C

Question: The induced e.m.f. in a rod of length l translating at a speed v making an angle θ with length l and perpendicular to magnetic field B is
(a) Blv
(b) Blv cos θ
(c) Blv sin θ 
(d) Blv tan θ

Answer: C

Question: Direction of current induced in a wire moving in a magnetic field is found using
(a) Fleming’s left found rule
(b) Fleming’s right hand rule
(c) Ampere’s rule
(d) Right hand clasp rule

Answer: B

Question: When the plane of the armature of an a.c. generator is parallel to the field. in which it is rotating
(a) both the flux linked and induced emf in the coil are zero.
(b) the flux linked with it is zero, while induced emf is maximum.
(c) flux linked is maximum while induced emf is zero.
(d) both the flux and emf have their respective maximum values.

Answer: B

Question: The self inductance associated with a coil is independent of
(a) current
(b) induced voltage
(c) time
(d) resistance of a coil 

Answer: D

Question: Which of the following does not use the application of eddy current ?
(a) Electric power meters
(b) Induction furnace
(c) LED lights
(d) Magnetic brakes in trains

Answer: C

Question: For magnetic breaking in trains, strong electromagnets are situated above the rails in some electrically powered trains. When the electromagnets are activated, the ...A... induced in the rails oppose the motion of the train. As there are no ... B... linkages, the ...C... effects is smooth.
Here, A, B and C refer to
(a) eddy currents, mechanical, breaking
(b) induced currents, thermal, accelerating
(c) induced emf, mechanical, accelerating
(d) eddy currents, thermal, flying

Answer: A

Question: The mutual inductance of a pair of coils is 0.75 H. If current in the primary coil changes from 0.5 A to zero in 0.01 s, find average induced e.m.f. in secondary coil
(a) 25.5 V
(b) 12.5 V
(c) 22.5 V
(d) 37.5 V

Answer: D

Question: A magnet is moved towards a coil (i) quickly (ii) slowly, then the induced e.m.f. is
(a) larger in case (i)
(b) smaller in case (i)
(c) equal in both the cases
(d) llarger or smaller depending upon the radius of the coil

Answer: A

Question: The self inductance associated with a coil is independent of
(a) current
(b) time
(c) induced voltage
(d) resistance of coil

Answer: D

Question: A moving conductor coil produces an induced e.m.f. This is in accordance with
(a) Lenz’s law
(b) Faraday’s law
(c) Coulomb’s law
(d) Ampere’s law

Answer: B

Question: Len’z law provides a relation between
(a) current and magnetic field.
(b) induced e.m.f. and the magnetic flux.
(c) force on a conductor in magnetic field.
(d) current and induced e.m.f.

Answer: B

Question: An inductor may store energy in
(a) its electric field
(b) its coils
(c) its magnetic field
(d) both in electric and magnetic fields

Answer: C

Question: The emf is induced in a single, isolated coil due to ...A...of flux through the coil by means of varying the current through the same coil. This phenomenon is called ...B...
Here, A and B refer to
(a) constancy, mutual induction
(b) change, self induction
(c) constancy, self induction
(d) changes, mutual induction

Answer: B

Question: Production of induced e.m.f. in a coil due to the changes of current in the same coil is
(a) self induction
(b) mutual induction
(c) dynamo
(d) none of these

Answer: A

Question: Eddy currents do not cause
(a) damping
(b) heating
(c) sparking
(d) loss of energy

Answer: C

Question: Two solenoids of same cross-sectional area have their lengths and number of turns in ratio of 1 : 2 both. The ratio of self-inductance of two solenoids is
(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) 1 : 4

Answer: B

Question: An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e.m.f. is independent of
(a) the strength of the magnet
(b) number of turns of coil
(c) the resistivity of the wire of the coil
(d) speed with which the magnet is moved

Answer: C

Question: The laws of electromagnetic induction have been used in the construction of a
(a) galvanometer
(b) voltmeter
(c) electric motor
(d) generator

Answer: D

Question: A cylindrical bar magnet is kept along the axis of a circular coil. On rotating the magnet about its axis, the coil will have induced in it
(a) a current
(b) no current
(c) only an e.m.f.
(d) both an e.m.f. and a current

Answer: B

Question: If in a galvanometer the coil is wound on a bad conductor, the eddy current will be
(a) zero 
(b) maximum
(c) minimum
(d) 50% of the actual value 

Answer: A

Question: Mutual induction is the production of induced e.m.f. in a coil due to the changes of current in the
(a) same coil
(b) neighbouring coil
(c) both (a) and (b)
(d) neither (a) nor (b)

Answer: B

Question: When the plane of the armature of a generator is parallel to the field. in which it is rotating
(a) both the flux linked and induced emf in the coil are zero.
(b) the flux linked with it is zero, while induced emf is maximum.
(c) flux linked is maximum while induced emf is zero.
(d) both the flux and emf have their respective maximum values.

Answer: B

Question: Whenever the magnetic flux linked with an electric circuit changes, an emf is induced in the circuit. This is called
(a) electromagnetic induction
(b) lenz’s law
(c) hysteresis loss
(d) kirchhoff’s laws

Answer: A

Question: Magnetic flux is
(a) total charge per unit area.
(b) total current through a surface.
(c) total number of magnetic field lines passing normally through given area.
(d) total e.m.f. in closed circuit.

Answer: C

Question: The self inductance of a coil is a measure of
(a) electrical inertia
(b) electrical friction
(c) induced e.m.f.
(d) induced current

Answer: A

Question: When strength of eddy currents is reduced, as dissipation of electrical energy into heat depends on the ...A... of the strength of electrical energy into heat depends on the ...A... of the strength of electric current heat loss is substantially ...B ... . Here, A and B refer to
(a) cube, increase
(b) inverse, increased
(c) inverse, decreased
(d) square, reduced

Answer: D

Question: The magnetic potential energy stored in a certain inductor is 25 mJ, when the current in the inductor is 60 mA. This inductor is of inductance
(a) 0.138 H
(b) 138.88 H
(c) 13.89 H
(d) None of these

Answer: C

Question: According to Faraday’s law of electromagnetic induction
(a) electric field is produced by time varying magnetic flux.
(b) magnetic field is produced by time varying electric flux.
(c) magnetic field is associated with a moving charge.
(d) None of these

Answer: A

Question: Certain galvanometers have a fixed core made of nonmagnetic metallic material, when the coil oscillates, ...A... generated in the core ...B... the motion and bring the coil to rest ...C... Here, A, B and C refer to
(a) induced emf, support, long time
(b) induced current, support, long time
(c) mechanical energy, oppose, long time
(d) eddy currents, oppose, quickly

Answer: D

Question: Induction furnace make use of
(a) self induction
(b) mutual induction
(c) eddy current
(d) None of these

Answer: C

Question: Two identical coaxial circular loops carry a current i each circulating in the same direction. If the loops approach each other, you will observe that the current in
(a) each increases
(b) each decreases
(c) each remains the same
(d) one increases whereas that in the other decreases

Answer: B

Question: The coils in resistance boxes are made from doubled insulated wire to nullify the effect of
(a) heating
(b) magnetism
(c) pressure
(d) self induced e.m.f.

Answer: D

Question: A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil This is because
(a) the magnetic field is constant
(b) the magnetic field is in the same plane as the circular coil and it may or may not vary.
(c) the magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is decreasing suitably.
(d) both (b) and (c)

Answer: D

Question: The pointer of a dead-beat galvanometer gives a steady deflection because
(a) eddy currents are produced in the conducting frame over which the coil is wound.
(b) its magnet is very strong.
(c) its pointer is very light.
(d) its frame is made of ebonite.

Answer: A

Question: According to Faraday’s law of electromagnetic induction
(a) electric field is produced by time varying magnetic flux.
(b) magnetic field is produced by time varying electric flux.
(c) magnetic field is associated with a moving charge.
(d) None of these

Answer: A

Question: A wire of length 50 cm moves with a velocity of 300 m/min, perpendicular to a magnetic field. If the e.m.f. induced in the wire is 2 V, the magnitude of the field in tesla is
(a) 2
(b) 5
(c) 0.8
(d) 2.5

Answer: C

Question: Eddy currents do not produce
(a) heat
(b) a loss of energy
(c) spark
(d) damping of motion

Answer: C

CUET Physics Alternating Current MCQs

Question: An A.C. source is connected to a resistive circuit. Which of the following is true?
(a) Current leads ahead of voltage in phase
(b) Current lags behind voltage in phase
(c) Current and voltage are in same phase
(d) Any of the above may be true depending upon the value of resistance.

Answer: C

Question: The electric mains supply in our homes and offices is a voltage that varies like a sine function with time such a voltage is called ... A... and the current driven by it in a circuit is called the ... B... Here, A and B refer to
(a) DC voltage, AC current 
(b) AC voltage, DC current 
(c) AC voltage, DC voltage 
(d) AC voltage, AC current

Answer: D

Question: The average power dissipated in a pure inductance is
(a) 1/2LI2 
(b) LI2 
(c) LI2 / 4 
(d) zero

Answer: D

Question: When an ac voltage of 220 V is applied to the capacitor C, then
(a) the maximum voltage between plates is 220 V. 
(b) the current is in phase with the applied voltage. 
(c) the charge on the plate is not in phase with the applied votage. 
(d) power delivered to the capacitor per cycle is zero.

Answer: D

Question: Power factor of the A. C. circuit varies between
(a) 0 to 0.5 
(b) 0.5 to 1 
(c) 0 to 1
(d) 1 to 2

Answer: C

Question: Alternating current cannot be measured by D.C. ammeter, because
(a) A. C. is virtual
(b) A. C. changes its direction
(c) A. C. cannot pass through D.C. ammeter
(d) average value of A. C for complete cycle is zero

Answer: D

Question: The capacitive reactance in an A.C. circuit is
(a) effective resistance due to capacity
(b) effective wattage
(c) effective voltage
(d) None of these

Answer: A

Question: A.C. power is transmitted from a power house at a high voltage as
(a) the rate of transmission is faster at high voltages 
(b) it is more economical due to less power loss
(c) power cannot be transmitted at low voltages 
(d) a precaution against theft of transmission lines

Answer: B

Question: The alternating current of equivalent value of I0√2 is
(a) peak current 
(b) r.m.s. current
(c) D.C. current 
(d) all of these

Answer: B

Question: The core of transformer is laminated to reduce
(a) flux leakage 
(b) hysteresis 
(c) copper loss  
(d) eddy current

Answer: D

Question: With increase in frequency of an A.C. supply, the inductive reactance
(a) decreases 
(b) increases directly with frequency
(c) increases as square of frequency 
(d) decreases inversely with frequency

Answer: B

Question: If the frequency of an A.C. is made 4 times of its initial value, the inductive reactance will
(a) be 4 times
(b) be 2 times 
(c) be half 
(d) remain the same

Answer: A

Question: Phase difference between voltage and current in a capacitor in an ac circuit is
(a) π  
(b) π/2
(c) 0 
(d) π/3

Answer: B

Question: With increase in frequency of an A.C. supply, the impedance of an L-C-R series circuit
(a) remains constant 
(b) increases 
(c) decreases 
(d) decreases at first, becomes minimum and then increases.

Answer: D

Question: A transformer is employed to
(a) convert A.C. into D.C. 
(b) convert D.C. into A.C. 
(c) obtain a suitable A.C. voltage
(d) obtain a suitable D.C. voltage

Answer: C

Question: For minimum dissipation of energy in the circuit the power factor should be
(a) large
(b) small 
(c) moderate 
(d) can not say 

Answer: A

Question: In series combination of R, L and C with an A.C. source at resonance, if R = 20 ohm, then impedence Z of the combination is 
(a) 20 ohm
(b) zero
(c) 10 ohm
(d) 400 ohm

Answer: A

Question: A coil of 40 henry inductance is connected in series with a resistance of 8 ohm and the combination is joined to the terminals of a 2 volt battery. The time constant of the circuit is 
(a) 20 seconds
(b) 5 seconds
(c) 1/5 seconds
(d) 40 seconds

Answer: B

Question: The transformer voltage induced in the secondary coil of a transformer is mainly due to
(a) a varying electric field
(b) a varying magnetic field
(c) the vibrations of the primary coil
(d) the iron core of the transformer

Answer: B

Question: If the frequency of an A.C. is made 4 times of its initial value, the inductive reactance will
(a) be 4 times
(b) be 2 times
(c) be half     
(d) remain the same

Answer: A

Question: In which of the following circuits the maximum power dissipation is observed?
(a) Pure capacitive circuit
(b) Pure inductive circuit
(c) Pure resistive circuit
(d) None of these

Answer: C

Question: Alternating currents can be produced by a
(a) dynamo
(b) choke coil 
(c) transformer 
(d) electric motor

Answer: A

Question: A transformer is based on the principle of
(a) mutual induction
 (b) self induction 
(c) Ampere’s law 
(d) X-ray crystallography

Answer: A

Question: Eddy currents in the core of transformer can't be developed by
(a) increasing the number of turns in secondary coil 
(b) taking laminated transformer
(c) making step down transformer 
(d) using a weak a.c. at high potential

Answer: B

Question: Of the following about capacitive reactance which is correct?
(a) The reactance of the capacitor is directly proportional to its ability to store charge 
(b) Capacitive reactance is inversely proportional to the frequency of the current
(c) Capacitive reactance is measured in farad 
(d) The reactance of a capacitor in an A.C. circuit is similar to the resistance of a capacitor in a D.C. circuit

Answer: B

Question: 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
(a) inductor increases
(b) resistor increases 
(c) capacitor increases 
(d) circuit increases

Answer: A

Question: Transformers are used
(a) in DC circuit only 
(b) in AC circuits only
(c) in both DC and AC circuits 
(d) neither in DC nor in AC circuits 

Answer: B

Question: The power factor in a circuit connected to an A.C. The value of power factor is 
(a) unity when the circuit contains an ideal inductance only
(b) unity when the circuit contains an ideal resistance only
(c) zero when the circuit contains an ideal resistance only
(d) unity when the circuit contains an ideal capacitance only

Answer: B

Question: An inductive circuit contains resistance of 10 ohms and an inductance of 2 henry. If an A.C. voltage of 120 Volts and frequency 60 Hz is applied to this circuit, the current would be nearly 
(a) 0.32 A
(b) 0.16 A
(c) 0.48 A
(d) 0.80 A

Answer: B

Question: When an ac voltage of 220 V is applied to the capacitor C, then
(a) the maximum voltage between plates is 220 V.
(b) the current is in phase with the applied voltage.
(c) the charge on the plate is not in phase with the applied votage.
(d) power delivered to the capacitor per cycle is zero

Answer: D

Question: The frequency of A.C. mains in India is
(a) 30 c/s 
(b) 50 c/s
(c) 60 c/s 
(d) 120 c/s

Answer: B

Question: The transformation ratio in the step-up transformer is
(a) one 
(b) greater than one
(c) less than one 
(d) the ratio greater or less than one depends on the other factor

Answer: B

Question: A capacitor acts as an infinite resistance for
(a) DC
(b) AC 
(c) DC as well as AC 
(d) neither AC nor DC

Answer: A

Question: The loss of energy in the form of heat in the iron core of a transformer is
(a) iron loss
 (b) copper loss 
(c) mechanical loss 
(d) None of these

Answer: A

Question: The transformer voltage induced in the secondary coil of a transformer is mainly due to
(a) a varying electric field
(b) a varying magnetic field 
(c) the vibrations of the primary coil 
(d) the iron core of the transformer

Answer:A

Question: A transformer is employed to
(a) convert A.C. into D.C.
(b) convert D.C. into A.C.
(c) obtain a suitable A.C. voltage
(d) obtain a suitable D.C. voltage

Answer: C

Question: With increase in frequency of an A.C. supply, the inductive reactance
(a) decreases
(b) increases directly with frequency
(c) increases as square of frequency
(d) decreases inversely with frequency

Answer: B

Question: The peak value of the a.c. current flowing throw a resistor is given by
(a) I0 = e0/R
(b) I = e/R 
(c) I0 = e0 
(d) I0 = R/e0

Answer: A

Question: In the case of an inductor
(a) voltage lags the current by Π/2 
(b) voltage leads the current by Π/2 
(c) voltage leads the current by  Π/3 
(d) voltage leads the current by Π/4

Answer: B

Question: A capacitor has capacitance C and reactance X, if capacitance and frequency become double, then reactance will be
(a) 4X 
(b) X/2 
(c) X/4
(d) 2X

Answer: C

Question: An LCR series circuit, connected to a source E, is at resonance. Then the voltage across
(a) R is zero 
(b) R equals applied voltage
(c) C is zero 
(d) L equals applied voltage

Answer: B

Question: Choose the correct option
Assertion : When the frequency of the AC source in an LCR circuit equals the resonant frequency, the reactance of the circuit is zero, and so there is no current through the inductor or the capacitor.
Reason : The net current in the inductor and capacitor is zero. 
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: D

Question: If an LCR series circuit is connected to an ac source, then at resonance the voltage across
(a) R is zero
(b) R equals the applied voltage
(c) C is zero
(d) L equals the applied voltage

Answer: B

Question: Alternating current can not be measured by D.C. ammeter, because
(a) A. C. is virtual 
(b) A. C. changes its direction 
(c) A. C. can not pass through D.C. ammeter 
(d) average value of A. C for complete cycle is zero

Answer: D

Question: An inductance L having a resistance R is connected to an alternating source of angular frequency ω The Quality factor Q of inductance is
(a) R/ ωL 
(b) (ωL/R)2 
(c) (R /ωL)½ 
(d) ωL/R

Answer: D

Question: In an L.C.R. series a.c. circuit, the current
(a) is always in phase with the voltage 
(b) always lags the generator voltage 
(c) always leads the generator voltage 
(d) None of these

Answer: D

Question: A current of 4A flows in a coil when connected to a 12V dc source. If the same coil is connected to a 12V, 50 rad/s a.c. source, a current of 2.4A flows in the circuit. Determine the inductance of the coil.
(a) 0.08 H
(b) 0.04 H
(c) 0.02 H
(d) 1 H

Answer: A

Question: In an L.C.R. series a.c. circuit, the current
(a) is always in phase with the voltage
(b) always lags the generator voltage
(c) always leads the generator voltage
(d) None of these

Answer: D

Question: An A.C. source is connected to a resistive circuit. Which of the following is true?
(a) Current leads ahead of voltage in phase 
(b) Current lags behind voltage in phase 
(c) Current and voltage are in same phase
(d) Any of the above may be true depending upon the value of resistance.

Answer: C

Question: In LCR circuit if resistance increases quality factor
(a) increases finitely 
(b) decreases finitely
(c) remains constant 
(d) None of these

Answer: B

Question: In an LCR series a.c. circuit, the voltage across each of the components, L, C and R is 50V. The voltage across the LC combination will be 
(a) 100 V
(b) 150 V
(c) 50 V 
(d) 0 V

Answer: D

Question: In general in an alternating current circuit
(a) the average value of current is zero
(b) the average value of square of the current is zero 
(c) average power dissipation is zero 
(d) the phase difference between voltage and current is zero

Answer: A

Question: Quantity that remains unchanged in a transformer is
(a) voltage 
(b) current 
(c) frequency  
(d) None of these

Answer: C

Question: If an LCR series circuit is connected to an ac source, then at resonance the voltage across
(a) R is zero 
(b) R equals the applied voltage
(c) C is zero 
(d) L equals the applied voltage

Answer: B

Question:  The loss of energy in the form of heat in the iron core of a transformer is
(a) iron loss           
(b) copper loss
(c) mechanical loss
(d) None of these

Answer: A

Question: The parallel combination of inductor and capacitor is called as 
(a) rectifier circuit  
(b) tank circuit
(c) acceptor circuit 
(d) filter circuit

Answer: B

Question: The capacitive reactance in an A.C. circuit is 
(a) effective resistance due to capacity
(b) effective wattage 
(c) effective voltage 
(d) None of these

Answer: A

Question: The graph between inductive reactance and frequency is
(a) parabola 
(b) straight line
(c) hyperbola 
(d) an arc of a circle

Answer: B

Question: The alternating current can be measured with the help of
(a) hot wire ammeter 
(b) hot wire voltmeter 
(c) moving magnet galvanometer 
(d) suspended coil type galvanometer

Answer: A

Question: A.C. power is transmitted from a power house at a high voltage as
(a) the rate of transmission is faster at high voltages
(b) it is more economical due to less power loss
(c) power cannot be transmitted at low voltages
(d) a precaution against theft of transmission lines

Answer: B