Electromagnetic Induction is an important concept in Class 12 Physics, forming the foundation for various applications in science and technology. It explains how electricity and magnetism are connected, enabling us to generate electrical energy and understand many modern devices. The topic is a key part of the curriculum and often appears in exams in the form of multiple-choice questions (MCQs).
At its core, electromagnetic induction deals with the process of generating an electromotive force (emf) or current in a conductor when it interacts with a changing magnetic field. This principle was discovered by Michael Faraday in the 19th century and is now used in generators, transformers, electric motors, and more. It plays a vital role in powering our homes, industries, and gadgets.
Faraday’s law of electromagnetic induction states that the emf induced in a circuit is directly proportional to the rate of change of magnetic flux through the circuit. Simply put, if the magnetic field passing through a conductor changes, an electric current is produced. Lenz’s law complements this by explaining the direction of the induced current, stating that it always opposes the change in magnetic flux that caused it.
For example, when a magnet is moved near a coil of wire, the magnetic flux through the coil changes, and this induces a current in the wire. Similarly, when a coil rotates in a magnetic field, it generates alternating current, forming the working principle of generators.
To understand electromagnetic induction better, it’s essential to study concepts such as:
- Magnetic Flux: The total magnetic field passing through a surface.
- Faraday’s Law: The quantitative relationship between changing magnetic flux and induced emf.
- Lenz’s Law: The direction of induced emf and current.
- Self-Induction: The property of a coil to oppose changes in its own current.
- Mutual Induction: The process where a change in current in one coil induces an emf in another nearby coil.
These ideas are tested in exams through practical and theoretical questions. MCQs on electromagnetic induction help students grasp the core concepts by offering quick, problem-based scenarios to analyze. These questions may include determining the direction of induced current using Fleming’s Right-Hand Rule, calculating emf using Faraday’s formula, or understanding the working of devices like transformers and generators.
Practicing MCQs is an effective way to build confidence and accuracy. It allows students to test their understanding, identify areas that need improvement, and prepare for board exams and competitive exams like JEE or NEET.
Do Check: Important Questions for Class 12 Physics Chapter 6 Electromagnetic Induction
Class 12 MCQs for Electromagnetic Induction
1. Which rule is used to determine the direction of current induced in a conductor moving through a magnetic field?
a) Ampere’s Rule
b) Fleming’s Left-Hand Rule
c) Fleming’s Right-Hand Rule
d) None of the above
Answer: c) Fleming’s Right-Hand Rule
Explanation: Fleming’s Right-Hand Rule states that if the thumb, forefinger, and middle finger of the right hand are held mutually perpendicular, the thumb points in the direction of motion of the conductor, the forefinger in the direction of the magnetic field, and the middle finger in the direction of the induced current.
2. A steady current flows through a solenoid connected to a battery. If an iron core is inserted into the solenoid, the current will:
a) Increase
b) Decrease
c) Remain the same
d) First increase, then decrease
Answer: b) Decrease
Explanation: The insertion of an iron core increases the solenoid’s inductance, which reduces the current for a given voltage because the opposition to the change in current increases.
3. The self-inductance of a coil is independent of:
a) Current
b) Time
c) Induced voltage
d) Resistance of the coil
Answer: d) Resistance of the coil
Explanation: Self-inductance depends only on the geometry and material of the coil, not on its resistance.
4. When a magnetic flux changes with time, the induced emf in a circuit is explained by:
a) Electromagnetic induction
b) Lenz’s Law
c) Hysteresis Loss
d) Kirchhoff’s Laws
Answer: a) Electromagnetic induction
Explanation: Electromagnetic induction occurs when the magnetic flux linked with a conductor changes, producing an emf.
5. According to Faraday’s law of electromagnetic induction:
a) Electric fields are produced by changing magnetic flux
b) Magnetic fields are produced by changing electric flux
c) Magnetic fields are associated with moving charges
d) None of these
Answer: a) Electric fields are produced by changing magnetic flux
Explanation: Faraday’s law states that a time-varying magnetic flux induces an electric field.
Do Check: NCERT Solutions for Class 12 Physics Chapter 6 Electromagnetic Induction
6. A coil wound on a rectangular frame has its linear dimensions doubled. If the number of turns per unit length remains the same, its self-inductance increases by a factor of:
a) 4
b) 8
c) 12
d) 16
Answer: b) 8
Explanation: Self-inductance depends on the square of the area and the number of turns. Doubling the dimensions increases the area fourfold, leading to an eightfold increase in inductance.
7. Polarity of the induced emf is determined by:
a) Ampere’s Law
b) Biot–Savart Law
c) Lenz’s Law
d) Fleming’s Right-Hand Rule
Answer: c) Lenz’s Law
Explanation: Lenz’s Law states that the direction of the induced emf opposes the cause producing it.
8. A coil’s self-inductance measures its:
a) Electrical inertia
b) Electrical friction
c) Induced emf
d) Induced current
Answer: a) Electrical inertia
Explanation: Self-inductance resists changes in the magnetic flux and current, behaving like inertia in an electrical system.
9. The unit of magnetic flux is:
a) Electric conductance
b) Magnetic flux
c) Magnetic flux density
d) Capacitance
Answer: b) Magnetic flux
Explanation: The SI unit of magnetic flux is the Weber (Wb).
10. The induced emf is independent of:
a) Change in flux
b) Time
c) Resistance of the coil
d) None of these
Answer: b) Time
Explanation: The induced emf depends on the rate of change of magnetic flux and the resistance of the coil, not directly on time.
Do Check: Electromagnetic Induction Previous Year Questions
11. A rectangular conductor is moved out of a magnetic field. The work done will be greater when the motion is:
a) Fast
b) Slow
c) The same in both cases
d) Cannot say
Answer: a) Fast
Explanation: Faster motion increases the rate of change of magnetic flux, resulting in higher emf and greater energy transfer.
12. Which law is used to measure the induced emf in a moving conductor?
a) Faraday’s Law
b) Lenz’s Law
c) Ampere’s Law
d) Coulomb’s Law
Answer: a) Faraday’s Law
Explanation: Faraday’s Law quantifies the induced emf due to a change in magnetic flux.
13. When the rate of change of current is unity, the induced emf is equal to:
a) Thickness of the coil
b) Number of turns in the coil
c) Coefficient of self-inductance
d) Total flux linked with the coil
Answer: c) Coefficient of self-inductance
Explanation: The induced emf is directly proportional to the rate of change of current and the coil’s self-inductance.
14. When a magnet is moved into a coil, the strength of the induced emf is independent of:
a) Strength of the magnet
b) Number of turns in the coil
c) Resistance of the wire
d) Speed of motion
Answer: c) Resistance of the wire
Explanation: Resistance does not affect the strength of the induced emf, but it influences the current produced.
15. Electromagnetic induction is the basis for the working of:
a) Galvanometer
b) Electric motor
c) Generator
d) Voltmeter
Answer: c) Generator
Explanation: Generators convert mechanical energy into electrical energy using electromagnetic induction.
16. The self-inductance of a solenoid depends on:
a) Length of the solenoid
b) Number of turns
c) Cross-sectional area
d) All of these
Answer: d) All of these
Explanation: The self-inductance is determined by the solenoid’s geometry and the number of turns.
17. A galvanometer pointer moves due to:
a) Induced current
b) Magnetic force
c) Resistance of the coil
d) None of these
Answer: a) Induced current
Explanation: The pointer deflection occurs due to the current induced in the coil.
Do Check: HC Verma Solutions Class 12 Chapter 16 Electromagnetic Induction
18. When a coil moves in a constant magnetic field, emf is:
a) Produced
b) Not produced
c) Produced only if the field varies
d) None of these
Answer: b) Not produced
Explanation: A moving coil in a constant magnetic field does not induce emf.
19. A change in magnetic flux produces:
a) Electric field
b) Magnetic field
c) Current only
d) None of these
Answer: a) Electric field
Explanation: Faraday’s law shows that a changing magnetic flux generates an electric field.
20. Which of these does NOT affect the strength of induced emf?
a) Number of turns
b) Magnetic field strength
c) Speed of motion
d) Coil resistance
Answer: d) Coil resistance
Explanation: Resistance affects the current but not the emf.
21. A solenoid connected to a battery generates a steady magnetic field. What happens if the battery voltage is doubled?
a) Field strength doubles
b) Field strength halves
c) Field strength remains constant
d) Field collapses
Answer: a) Field strength doubles
Explanation: Magnetic field strength is proportional to the current, which depends on the voltage.
22. The emf induced when the magnetic flux changes is called:
a) Self-induction
b) Mutual induction
c) Electromagnetic induction
d) None of these
Answer: c) Electromagnetic induction
Explanation: This phenomenon occurs when a conductor experiences a changing magnetic flux.
23. When a coil rotates in a magnetic field, emf induced is maximum when the angle is:
a) 0°
b) 45°
c) 90°
d) 180°
Answer: c) 90°
Explanation: The rate of change of flux is maximum at 90°.
24. What opposes the cause of induced emf?
a) Faraday’s Law
b) Coulomb’s Law
c) Lenz’s Law
d) Ampere’s Law
Answer: c) Lenz’s Law
Explanation: Lenz’s Law states that the induced emf opposes the change in flux.
25. The SI unit of inductance is:
a) Tesla
b) Weber
c) Henry
d) Farad
Answer: c) Henry
Explanation: Inductance is measured in Henry (H).
