Chapter 6: Electromagnetic Induction Assertion Reason
These questions of two statements each, printed as Assertion and Reason. While answering these Questions you are required to choose any one of the following four responses.
(A) If both Assertion & Reason are true & the Reason is a correct explanation of the Assertion.
(B) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
(C) If Assertion is true but the Reason is false.
(D) If Assertion & Reason both are false.
Q.1 Assertion : The mutual inductance M between two coils of self inductances L1 and L2 is given by M £ .
Reason : The energy density (i.e. energy per unit volume) at an point, where the magnetic field B is given by .
(1) A (2) B (3) C (4) D
Answer: 2
Q.2 Assertion : Voltage across L (see figure) at t = 0 is E.
Reason : Because E = VL + VR and at t = 0, i = 0
(1) A (2) B (3) C (4) D
Answer: 1
Q.3 Assertion : At any instant, if the current through an inductor is zero, then the induced emf may not be zero.
Reason : An inductor tends to keep the flux (i.e. current) constant.
(1) A (2) B (3) C (4) D
Answer: 2
Q.4 Assertion : Due to high inductance of any coil, the current attains it peak value relatively late in it.
Reason : Due to self induction, coil opposses the flow of current through it.
(1) A (2) B (3) C (4) D
Answer: 3
Q.5 Assertion : A current is flowing through a coil with 5 volt battery. If self inductance of coil is increased then circuit takes more time to acquires its current peak.
Reason : Inductance strongly opposses the flow of current through it.
(1) A (2) B (3) C (4) D
Answer: 3
Q.6 Assertion : Unlike charges are projected in opposite direction in transverse magnetic field, then they are deflected in same directions.
Reason : If a voltmeter connected across two peripheral points of faraday copper disc generator, its reading is zero.
(1) A (2) B (3) C (4) D
Answer: 2
Q.7 Assertion : Faraday’s copper disc generator is based on dynamic electromagnetic induction.
Reason : Alternating current generator is based on periodic electromagnetic induction.
(1) A (2) B (3) C (4) D
Answer: 2
Q.8 Assertion : When a conducting rod moves in uniform transverse magnetic field with uniform speed which is perpendicular to its length, then potential difference may developed across its ends.
Reason : In any conductor, free electrons and free positive ions are available.
(1) A (2) B (3) C (4) D
Answer: 3
Q.9 Assertion : If a steel core is used in a transformer in place of soft iron core then hyesterisis losses are increased.
Reason : Steel core is easily magnetised but it is easily not demagnetised by the alternating magnetic field.
(1) A (2) B (3) C (4) D
Answer: 3
Q.10 Assertion : A step up transformer can also as a step down transformer.
Reason : This is because
(1) A (2) B (3) C (4) D
Answer: 1
Q.11 Assertion : Magnetic flux through the wood ring changes with respect to time then an emf is induced in it.
Reason : Two basic difference between an electric line and a magnetic line of force is that former is discontinuous and latter is continuous or endless.
(1) A (2) B (3) C (4) D
Answer: 2
Q.12 Assertion : When a bar magnet moves along the axis of conducting coil, then its kinetic energy and a part of magnetic energy of bar magnet is converted into electrical energy of coil.
Reason : Lenz law is based on conservation of energy.
(1) A (2) B (3) C (4) D
Answer: 1
Q.13 Assertion : If magnetic flux through any circuit is changes then an emf in induced in it. This emf is equal to negative of rate of change of flux.
Reason : Direction of induced emf is always such that it always opposes the cause by which it is produced.
(1) A (2) B (3) C (4) D
Answer: 3
Q.14 Assertion : The quantity L/R possesses dimension of time.
Reason : To reduce the rate of growth of current through a solenoid, we should increase the time constant (L/R).
(1) A (2) B (3) C (4) D
Answer: 1
Q.15 Assertion : An electric field is induced in a closed loop where magnetic flux is varied. The induced is not a conservative field.
Reason : The line integral around the closed loop is non zero.
(1) A (2) B (3) C (4) D
Answer: 1
Q.16 Assertion : When we consider mutual induction of two coils, their self induction is taken as zero.
Reason : Self induction and mutual induction are effective simultaneously.
(1) A (2) B (3) C (4) D
Answer: 4
Q.17 Assertion : In a given situation, the direction of induced current given by Lenz’s Law and Fleming’s right hand rule is the same.
Reason : Statement of both the laws is the same.
(1) A (2) B (3) C (4) D
Answer: 3
Q.18 Assertion : An inductor can not have zero resistance.
Reason : This is because inductor has to be made up of some material, which must have some resistance.
(1) A (2) B (3) C (4) D
Answer: 1
Q.19 Assertion : Whenever magnetic flux linked with the coil changes with respect to time, then an emf is induced in it.
Reason : According to lenz law, the direction of induced current in any coil in such a way that it always oposses the cause by which it is produced.
(1) A (2) B (3) C (4) D
Answer: 2
Q.20 Assertion : Electromagnets are made of soft iron.
Reason : Soft iron has low retentivity and low coercive force.
(1) A (2) B (3) C (4) D
Answer: 1
Q.21 Assertion : A thin aluminium disc, spinning freely about a central pivot, is quickly brought to rest when placed between the poles of a strong U-shaped magnet.
Reason : A current induced in a disc rotating in a magnetic field produces a torque which tends to oppose the disc’s motion.
(1) A (2) B (3) C (4) D
Answer: 1
Q.22 Assertion : We use a thick wire in the secondary of a step down transformer to reduce the produced heat.
Reason : When the plane of the armature coil is parallel to the line of force of magnetic field, the magnitude of induced e.m.f. is maximum.
(1) A (2) B (3) C (4) D
Answer: 2
Q.23 Assertion : A thin aluminum disc, spinning freely about a central pivot, is quickly brought to rest when placed between the poles of a strong U-shaped magnet.
Reason : A current induced in a disc rotating in a magnetic field produces a force which tends to oppose the motion of the disc.
(1) A (2) B (3) C (4) D
Answer: 1
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Class 12 Physics Notes