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Physics Assertion (A) & Reason (B) MCQ

Electromagnetic Induction · Gujarat Board (GSEB) STD 12 Science (GSEB - English Medium). 14 questions.

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Assertion (A) & Reason (B) MCQ

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14 questions · timed · auto-graded

Question 11 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): Inductance coil are made of copper.
Reason (R): Induced current is more in wire having less resistance.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

The inductance coils made of copper will have very small ohmic resistance. Due to change in magnetic flux a large induced current will be produced in such an inductance, which will offer appreciable opposition to the flow of current.

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Question 21 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): When number of turns in a coil doubled, coefficient of self inductance of the coil becomes four times.
Reason (R): Coefficient of self inductance is proportional to the square of number of turns.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

The coefficient of self inductance of the coil is given by $\text{L}=\frac{\mu_0\text{N}^2\text{A}}{\text{l}}$

where N is number of turns, l is length of the coil and A is area of coil, so $\text{L}\propto\text{N}^2.$

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Question 31 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): An artificial satellite with a metal surface is moving above the earth in a circular orbit. A current will be induced in satellite if the plane of the orbit is inclined to the plane of the equator.
Reason (R): The current will be induced only when the speed of satellite is more than 8km/ sec.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

When the satellite move in inclined plane with equatorial plane the value of magnetic field will change both in magnitude and direction. Due to this, the magnetic flux through the satellite will change and hence induced currents will be produced in the metal of the satellite. But no current will induce if satellite orbits in the equatorial plane because the magnetic flux does not change through the metal of the satellite in this plane.

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Question 41 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): An induced current is developed when the number of magnetic lines of force associated with conductor is changed.
Reason (R): An induced current develop in a conductor moved in a direction parallel to the magnetic field.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

An induced current develop in a conductor cannot moved in a direction parallel to magnetic field. This is because when the conductor moved in a direction parallel to magnetic field, amount of flux linked with the conductor does not change. Thus the induced current develops only when conductor cuts the lines of magnetic force. The direction of flow of induced current can also be found by applying Fleming's right hand rule, when the direction of motion of conductor inside the magnetic field and the direction of magnetic field action on it are known.

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Question 51 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): Changing magnetic flux can produce induced e.m.f.
Reason (R): Faraday established induced e.m.f. experimentally.
Answer
  1. Both A and Rare true but R is NOT the correct explanation of A.

Explanation: 

E.m.f. induces, when there is change in magnetic flux. The magnitude of induced e.m.f. depends upon the rate at which the magnetic flux changes. When magnetic flux is steady or constant no e.m.f. is induced. Faraday did experiment in which, there is relative motion between the coil and magnet, the flux linked with the coil changes and e.m.f. induces.

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Question 61 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): Self-inductance is called the inertia of electricity.
Reason (R): Self-inductance is the phenomenon, according to which an opposing induced e.m.f. is produced in a coil as a result of change in current or magnetic flux linked with the coil.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

Self-inductance of a coil is its property by virtue of which the coil opposes any change in the current flowing through it. It is because, the induced emf produced opposes the change in current. For this reason, self induction is called inertia of electricity.

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Question 71 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): Induced e.m.f. depends on number of turns and area of the coil.
Reason (R): Induced e.m.f. increases with increase in number of turns of coil.
Answer
  1. Both A and Rare true but R is NOT the correct explanation of A.

Explanation: 

According to Faraday's law, the induced e.m.f.

$\varepsilon=\frac{-\text{d(N}\phi)}{\text{dt}}=-\frac{\text{d(NBA)}}{\text{dt}}=-\text{NA}\frac{\text{dB}}{\text{dt}}.$

Thus the induced e.m.f. depends on the rate of change of magnetic flux, number of tums of coil and area of the coil. If any of these factor increases (or decreases) then induced e.m.f. also increases (or decreases).

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Question 81 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): An induced emf is generated when magnet is withdrawn from the solenoid.
Reason (R): The relative motion between magnet and solenoid induces emf.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

According to Faraday's law of electromagnetic induction, induced emf will be generated in the solenoid because of the relative motion between magnet and solenoid.

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Question 91 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): When two coils are wound on each other, the mutual induction between the coils is maximum.
Reason (R): Mutual induction does not depend on the orientation of the coils.
Answer
  1. A is true but R is false.

Explanation: 

The manner in which the two coils are oriented, determines the coefficient of coupling between them i.e., $\text{k}=\sqrt{\frac{\text{M}}{\text{L}_1\text{L}_2}}$ where L1 and L2 are self inductance of two coils. When the two coils are wound on each other, the coefficient of coupling is maximum and hence mutual inductance between the coil is maximum.

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Question 101 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): Tile coil in the resistance boxes are made by doubling the wire.
Reason (R): Thick wire is required in resistance box.
Answer
  1. A is true but R is false.

Explanation: 

The coil in the resistance boxes are made from double wire. Due to this current in two wires flows in opposite directions i.e., magnetic flux linked with the each coil cancel each other. Thus, no e.m.f. is induced in the resistance.

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Question 111 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): Acceleration of a magnet falling through a copper ring decreases.
Reason (R): The induced current produced in a circuit always flow in such direction that it opposes the change or the cause that produced it.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

Both the assertion and reason are true and reason is the correct explanation of assertion. When the magnet falls, the magnetic flux through the copper ring increases and induced e.m.f. is produced in the ring. The induced emf so produced, opposes the motion of falling magnet. Therefore, the acceleration of the falling

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Question 121 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): An aircraft flies along the meridian, the potential develops at the ends of its wings.
Reason (R): Whenever there is change in the magnetic flux e.m.f. induces.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

As the aircraft flies, magnetic flux changes through its wings due to the vertical component of the earth's magnetic field. Due to this, induced emf is produced across the wings of the aircraft.

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Question 131 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): The resistance of a coil for direct current is 5 ohms. An alternating current is sent through it. The resistance will remain same.
Reason (R): The resistance of a coil does not depend upon nature of current.
Answer
  1. A is false and R is also false.

Explanation: 

Both assertion and reason are false.

When an alternating current is sent through the coil then effective resistance of the coil will be $\sqrt{\text{R}^2+(\omega\text{L})^2}$ while it was only R for direct current i.e., effective resistance of coil will increases for A.C.

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Question 141 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): A copper sheet is placed in a magnetic field. If we pull it out of the field or push it into the field, we experience an opposing force.
Reason (R): According to Lenz's law, eddy current produced in sheet opposes the motion of the sheet.
Answer
  1. Both A and R are true and R is the correct explanation of A.

Explanation: 

When we pull a copper plate out of the magnetic field or push it into the magnetic field, magnetic flux linked with the plate changes. As a result of this eddy currents are produced in the plate which oppose its motion (according to Lenz's law).

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