Grade 12 : Physics - Electromagnetic Induction (Set 1)

Question 1

What is the standard SI unit of magnetic flux?

Accepted Answer

B) Weber

Answer

A) Tesla

Answer

C) Henry

Answer

D) Ampere

Question 2

A flat coil is oriented perpendicularly to a constant magnetic field.

A circular coil of surface area $0.4m^2$ is placed perpendicular to a uniform magnetic field of magnitude 0.5 T. What is the total magnetic flux passing through the coil?

Accepted Answer

B) 0.2 Wb

Answer

A) 0.1 Wb

Answer

C) 0.8 Wb

Answer

D) 2.0 Wb

Question 3

According to Faraday's law of electromagnetic induction, the magnitude of induced electromotive force (EMF) in a closed circuit is directly proportional to which quantity?

Accepted Answer

C) The rate of change of magnetic flux through the circuit

Answer

A) The magnetic field strength only

Answer

B) The total electrical resistance of the circuit

Answer

D) The static magnetic flux enclosed by the circuit

Question 4

Lenz's law, which determines the direction of an induced current, is a direct manifestation of which fundamental conservation law?

Accepted Answer

B) Law of conservation of energy

Answer

A) Law of conservation of electric charge

Answer

C) Law of conservation of linear momentum

Answer

D) Law of conservation of angular momentum

Question 5

A single loop of wire is situated in a time-varying magnetic environment.

A loop of wire experiences a decrease in magnetic flux from 0.15 Wb to 0.05 Wb in a time interval of 0.02 s. What is the magnitude of the average induced EMF in the loop?

Accepted Answer

B) 5.0 V

Answer

A) 2.0 V

Answer

C) 10.0 V

Answer

D) 0.1 V

Question 6

What is the SI unit used to measure self-inductance and mutual inductance?

Accepted Answer

D) Henry (H)

Answer

A) Weber (Wb)

Answer

B) Tesla (T)

Answer

C) Volt-second (V s)

Question 7

An inductor with self-inductance $L = 0.4 ext{ H}$ carries a current that changes at a uniform rate of 15 A/s. What is the magnitude of the induced EMF across the inductor?

Accepted Answer

A) 6.0 V

Answer

B) 3.75 V

Answer

C) 60.0 V

Answer

D) 0.026 V

Question 8

How much magnetic potential energy is stored in an inductor of inductance 2.0 H when carrying a steady current of 4.0 A?

Accepted Answer

B) 16.0 J

Answer

A) 8.0 J

Answer

C) 32.0 J

Answer

D) 4.0 J

Question 9

A conducting rod slides horizontally perpendicular to a magnetic field vector.

A straight conducting rod of length 0.5 m moves at a constant speed of 12 m/s perpendicular to a uniform magnetic field of magnitude 0.3 T. What is the induced motional EMF across the ends of the rod?

Accepted Answer

B) 1.8 V

Answer

A) 0.18 V

Answer

C) 3.6 V

Answer

D) 7.2 V

Question 10

If a flat circular loop is placed inside a uniform magnetic field $B$, at what angle $ heta$ between the area vector (normal to the loop) and the field direction is the net magnetic flux equal to zero?

Accepted Answer

C) $90^\circ$

Answer

A) $0^\circ$

Answer

B) $45^\circ$

Answer

D) $180^\circ$

Question 11

What are the closed loops of electric currents induced within solid metallic blocks when subject to a changing magnetic field called?

Accepted Answer

C) Eddy currents

Answer

A) Displacement currents

Answer

B) Direct currents

Answer

D) Surface charges

Question 12

Why are the iron cores of transformers and AC generators constructed from thin insulated laminations rather than solid iron blocks?

Accepted Answer

B) To minimize energy loss caused by eddy currents

Answer

A) To increase overall structural flexibility

Answer

C) To increase the magnetic flux density

Answer

D) To reduce the resistance of primary windings

Question 13

A rectangular generator coil with 50 turns and an area of $0.02m^2$ rotates at an angular frequency of 100 rad/s in a uniform magnetic field of 0.4 T. What is the peak amplitude of the induced EMF?

Accepted Answer

B) 40 V

Answer

A) 20 V

Answer

C) 80 V

Answer

D) 400 V

Question 14

Two coaxial solenoids have a mutual inductance $M$. If the total number of turns in both solenoids is doubled while keeping their physical dimensions unchanged, what happens to the mutual inductance?

Accepted Answer

C) It quadruples (increases by 4 times)

Answer

A) It remains unchanged

Answer

B) It doubles

Answer

D) It is reduced by half

Question 15

A coil of self-inductance $L = 50 ext{ mH}$ carries a steady current of 2.0 A. What is the total magnetic flux linkage ($\Phi_{ ext{total}} = N \Phi$) passing through the coil?

Accepted Answer

B) 0.10 Wb

Answer

A) 0.05 Wb

Answer

C) 1.00 Wb

Answer

D) 100.0 Wb

Question 16

What physical quantity represents magnetic flux per unit perpendicular area?

Accepted Answer

C) Magnetic field strength (Magnetic flux density)

Answer

A) Magnetic permeability

Answer

B) Magnetic susceptibility

Answer

D) Self-inductance

Question 17

A single square loop of side length 0.1 m is placed perpendicular to a magnetic field. The magnetic field increases uniformly from 0.2 T to 0.8 T over 0.3 s. What is the magnitude of the induced EMF?

Accepted Answer

B) 0.02 V

Answer

A) 0.01 V

Answer

C) 0.20 V

Answer

D) 0.06 V

Question 18

In a simple series RL circuit connected to a DC source, what is the formula for the inductive time constant $ au$?

Accepted Answer

B) $	au = \frac{L}{R}$

Answer

A) $	au = R L$

Answer

C) $	au = \frac{R}{L}$

Answer

D) $	au = \frac{1}{R L}$

Question 19

A vertical bar magnet falls with its North pole facing down towards a horizontal copper loop.

A bar magnet is dropped vertically through a fixed horizontal conductive copper ring. How does the downward acceleration $a$ of the falling magnet compare to free-fall acceleration $g$ while entering the ring?

Accepted Answer

C) $a < g$

Answer

A) $a = g$

Answer

B) $a > g$

Answer

D) $a = 0$

Question 20

Which of the following represents the dimensional formula for magnetic flux in terms of primary fundamental dimensions (M, L, T, A)?

Accepted Answer

A) $[	ext{M L}^2 	ext{T}^{-2} 	ext{A}^{-1}]$

Answer

B) $[	ext{M L}^2 	ext{T}^{-1} 	ext{A}^{-2}]$

Answer

C) $[	ext{M L T}^{-2} 	ext{A}^{-1}]$

Answer

D) $[	ext{M L}^2 	ext{T}^{-2} 	ext{A}^{-2}]$