Chapter-6 Electromagnetic Induction — Online MCQ Test
PHYSICS · CLASS 12 SECOND PUC · Karnataka State Board
Practice Chapter-6 Electromagnetic Induction with a free chapter-wise online MCQ test.
This chapter covers: Faraday's laws - Lenz's law - motional EMF - self induction - mutual induction.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-6 Electromagnetic Induction — Important Questions & Answers
According to Faraday's law of electromagnetic induction, the induced EMF in a coil is equal to:
- A. The rate of change of magnetic flux through the coil
- B. The magnetic flux through the coil
- C. The resistance of the coil multiplied by current
- D. The number of turns multiplied by magnetic field
Answer: A. The rate of change of magnetic flux through the coil
Faraday's law states that induced EMF = -dΦ/dt, which is the negative rate of change of magnetic flux through the coil.
Faraday's law states that induced EMF = -dΦ/dt, which is the negative rate of change of magnetic flux through the coil.
Which law determines the direction of induced current in a conductor moving through a magnetic field?
- A. Ohm's law
- B. Lenz's law
- C. Ampere's law
- D. Coulomb's law
Answer: B. Lenz's law
Lenz's law states that the direction of induced current is such that it opposes the change in magnetic flux that produced it.
Lenz's law states that the direction of induced current is such that it opposes the change in magnetic flux that produced it.
The SI unit of magnetic flux is:
- A. Tesla
- B. Ampere
- C. Weber
- D. Henry
Answer: C. Weber
Magnetic flux is measured in Weber (Wb), where 1 Wb = 1 Tesla × meter².
Magnetic flux is measured in Weber (Wb), where 1 Wb = 1 Tesla × meter².
Self-inductance of a coil is the phenomenon where:
- A. EMF is induced in one coil due to changing current in another coil
- B. EMF is induced in a coil due to changing current in the same coil
- C. EMF is induced due to changing magnetic field outside the coil
- D. Current flows without any EMF being induced
Answer: B. EMF is induced in a coil due to changing current in the same coil
Self-inductance is when a changing current in a coil induces an EMF in the same coil, opposing the change in current.
Self-inductance is when a changing current in a coil induces an EMF in the same coil, opposing the change in current.
A rectangular loop is placed in a uniform magnetic field. If the magnetic field is perpendicular to the plane of the loop and remains constant, the induced EMF will be:
- A. Maximum
- B. Minimum (zero)
- C. Increasing with time
- D. Equal to BL²
Answer: B. Minimum (zero)
Since magnetic flux is constant (uniform field, perpendicular to loop, no change), dΦ/dt = 0, so induced EMF = 0.
Since magnetic flux is constant (uniform field, perpendicular to loop, no change), dΦ/dt = 0, so induced EMF = 0.
A conductor of length L moves with velocity v perpendicular to a magnetic field B. The motional EMF induced is:
- A. BLv
- B. B/Lv
- C. BLv²
- D. BL/v
Answer: A. BLv
The motional EMF is given by ε = BLv, where the conductor moves perpendicular to the magnetic field.
The motional EMF is given by ε = BLv, where the conductor moves perpendicular to the magnetic field.
When a magnet falls through a conducting pipe, its acceleration is less than g because:
- A. Air resistance opposes motion
- B. Induced currents in the pipe create a magnetic field opposing the motion
- C. The magnet's weight decreases
- D. The pipe exerts a direct magnetic force
Answer: B. Induced currents in the pipe create a magnetic field opposing the motion
As the magnet falls, induced EMF creates currents that produce a magnetic field opposing the change (Lenz's law), creating an upward force.
As the magnet falls, induced EMF creates currents that produce a magnetic field opposing the change (Lenz's law), creating an upward force.
A rectangular coil ABCD is partially inserted into a magnetic field region. As it moves further into the field, which side experiences maximum motional EMF?
- A. The side completely in the field
- B. The side at the boundary (cutting field lines)
- C. The side parallel to motion
- D. All sides experience equal EMF
Answer: B. The side at the boundary (cutting field lines)
Only the side crossing the boundary between field and no-field regions cuts magnetic field lines, so it experiences maximum EMF.
Only the side crossing the boundary between field and no-field regions cuts magnetic field lines, so it experiences maximum EMF.
A rectangular loop with dimensions a×b moves with velocity v perpendicular to a magnetic field B. The motional EMF developed is Bvb (b is the width perpendicular to motion). Which statement is correct about energy considerations?
- A. Mechanical work done equals electrical energy dissipated
- B. Mechanical work is greater than electrical energy dissipated
- C. Electrical energy exceeds mechanical work input
- D. No relationship exists between mechanical work and electrical energy
Answer: A. Mechanical work done equals electrical energy dissipated
By energy conservation, mechanical work done against magnetic force equals electrical energy (I²R) dissipated in the loop's resistance.
By energy conservation, mechanical work done against magnetic force equals electrical energy (I²R) dissipated in the loop's resistance.
Two coils A and B have the same self-inductance L and mutual inductance M between them. When connected in series aiding configuration, their combined inductance is L_series. When connected in series opposing configuration, their combined inductance is L_series'. The relationship is:
- A. L_series + L_series' = 4L
- B. L_series - L_series' = 4M
- C. L_series·L_series' = (L² - M²)
- D. L_series/L_series' = (L + M)/(L - M)
Answer: B. L_series - L_series' = 4M
Series aiding: L_series = L + L + 2M = 2L + 2M; Series opposing: L_series' = 2L - 2M; Difference: L_series - L_series' = 4M.
Series aiding: L_series = L + L + 2M = 2L + 2M; Series opposing: L_series' = 2L - 2M; Difference: L_series - L_series' = 4M.