A
are straight lines parallel to the magnet
B
start at the north pole and end at the south pole
C
start at the south pole and end at the north pole outside the magnet
D
form closed loops, going from N to S outside the magnet and from S to N inside it

Q102. AI-generated practice Single-correct MCQ Easy

A bar magnet is cut into two pieces perpendicular to its length. Each piece:

A
loses its magnetism completely
B
has two north poles
C
has only one pole
D
is a complete magnet with its own north and south poles

Q103. AI-generated practice Single-correct MCQ Medium

A bar magnet of magnetic moment 2 A m² is placed in a uniform magnetic field of 0.15 T with its axis at 30° to the field. The torque on it is:

A
0.3 N m
B
0.075 N m
C
0.15 N m
D
0.26 N m

Q104. AI-generated practice Single-correct MCQ Medium

A short bar magnet of magnetic moment 1.2 A m² is in air. The magnetic field at a point on its axis 10 cm from its centre is (μ₀/4π = 10^-7 T m/A):

A2.4 × 10^-6 T
B2.4 × 10^-4 T
C4.8 × 10^-4 T
D1.2 × 10^-4 T

Q105. AI-generated practice Single-correct MCQ Medium

At a point on the equatorial line of a short bar magnet, the magnetic field is directed:

A
opposite to the magnetic moment of the magnet
B
perpendicular to the magnet, towards it
C
perpendicular to the magnet, away from it
D
along the magnetic moment

Q106. AI-generated practice Single-correct MCQ Hard

A bar magnet of magnetic moment m is cut into two equal halves perpendicular to its length. The magnetic moment of each half is:

A
2m
B
m/4
C
m/2
D
m

Q107. AI-generated practice Single-correct MCQ Medium

A thin straight bar magnet of magnetic moment m is bent into a semicircle. Its new magnetic moment is:

A
m/π
B
2m/π
C
m
D
m/2

Q108. AI-generated practice Single-correct MCQ Medium

The work done in rotating a magnet of moment 1.5 A m² slowly from the direction of a uniform field of 0.2 T to the opposite direction is:

A
zero
B
0.3 J
C
0.15 J
D
0.6 J

Q109. AI-generated practice Single-correct MCQ Hard

A small magnet oscillating in a uniform magnetic field has a time period T. If the field is made four times stronger, the new time period is:

A
T/4
B
4T
C
T/2
D
2T

Q110. AI-generated practice Single-correct MCQ Easy

Gauss's law for magnetism states that the net magnetic flux through any closed surface is:

A
zero
Bμ₀ times the enclosed pole strength
C
equal to the magnetic moment inside
Dμ₀ times the enclosed current

Q111. AI-generated practice Single-correct MCQ Medium

A current-carrying solenoid behaves like a bar magnet because:

A
it has a uniform field outside it
B
its field lines start at one end and end at the other
C
it has a magnetic moment NIA and its external field resembles that of a bar magnet
D
it contains magnetic monopoles at its ends

Q112. AI-generated practice Single-correct MCQ Medium

The potential energy of a magnetic dipole in a uniform magnetic field is minimum when:

A
its moment is antiparallel to the field
B
it is at 45° to the field
C
its moment is perpendicular to the field
D
its moment is parallel to the field

Q113. AI-generated practice Single-correct MCQ Hard

A short bar magnet and a small current loop have equal magnetic moments. At large distances, their magnetic fields are:

A
the same in magnitude and direction
B
different, because only the magnet obeys the inverse-cube law
C
the same only along the axis
D
different, because the loop has no poles

Q114. AI-generated practice Single-correct MCQ Medium

At a large distance r along its axis, the magnetic field of a short bar magnet varies as:

A1/r²
B1/r³
C
1/r
D1/r⁴

Q115. AI-generated practice Numerical value Easy

A magnet of magnetic moment 0.5 A m² is placed in a uniform field of 0.4 T. If the maximum torque on it is x × 10^-1 N m, find x.

Q116. AI-generated practice Numerical value Medium

A short bar magnet has a magnetic moment of 2 A m². If the magnetic field at a point on its axis 20 cm from its centre is x × 10^-5 T, find x. (μ₀/4π = 10^-7 T m/A)

Q117. AI-generated practice Numerical value Medium

A magnet of moment 2.5 A m² is rotated slowly from the direction of a uniform field of 0.32 T to a direction perpendicular to it. If the work done is x × 10^-1 J, find x.

Q118. AI-generated practice Numerical value Hard

A small bar magnet oscillates in a uniform magnetic field with a time period of 2 s. Find the time period (in seconds) when the field is reduced to one quarter of its original value.

Q119. AI-generated practice Assertion–Reason Medium

Assertion (A): The net magnetic flux through any closed surface is zero.
Reason (R): Magnetic field lines are crowded together near the poles of a bar magnet.

A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is not the correct explanation of A
C
A is true but R is false
D
A is false but R is true

Q120. AI-generated practice Assertion–Reason Hard

Assertion (A): The magnetic field lines of a bar magnet start at its north pole and end at its south pole.
Reason (R): Magnetic field lines form continuous closed loops.

A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is not the correct explanation of A
C
A is true but R is false
D
A is false but R is true