ASSIGNMENT
PHYSICS
JEE (MAIN + ADVANCED) 2025
ENTHUSIAST COURSE
PHASE : TNAS & TMAS
REVISION ASSIGNMENT # 15
M.M. : 62
TIME : 60 Min.
SECTION-I (i) (Maximum Marks:15)
Single Correct Answer Type 5 Q. [3 M (–1)]
1.
A donut-shaped permanent magnet (magnetization parallel to the axis) can slide frictionlessly on a
vertical rod. Treat the magnets as dipoles, with mass md and dipole moment M. When we put two back
to back magnets on the rod the upper one will float. At what height z does it float?
(A)
2.
2 μ 0M 2
[
]
3 π md g
1/4
(B)
6 μ 0M 2
[
]
π md g
1/4
(C)
3 μ 0M 2
[
]
2 π md g
1/4
(D)
μ 0M 2
[
]
6 π md g
1/4
A thin uniform ring of mass m and having electric charge Q uniformly distributed rotates around an axis
perpendicular to its plane and going through its center. The angular momentum of the ring is 7.5 × 10 –4
kg-m2/s. The ring is in a homogeneous magnetic field of a field strength of 0.1 T and the lines of the
magnetic induction are parallel with the plane of the ring. Torque exerted on the ring is ? [The specific
charge (charge-mass ratio) of the ring is Q/m = 10 –5 C/kg].
(A) 3.75 × 10 –10 (N-m) upward along the plane
(B) 3.75 × 10 –10 (N-m) downward along the plane
(C) 7.5 × 10 –10 (N-m) upward along the plane
(D) None of these
3.
A wire of radius R, carries current uniformly distributed over its cross section. The total current carried
by the wire is I. The magnetic energy per unit length inside the wire is
(A) μ 0 I 2
4π
PHYSICS / ASSIGNMENT # 15
(B) μ 0 I 2
8π
(C) μ 0 I 2
2π
(D) μ 0 I 2
16 π
E-1/8
JEE (MAIN + ADVANCED) 2025
ENTHUSIAST COURSE
PHASE : TNAS & TMAS
ASSIGNMENT
4.
The coil in a moving coil Galvanometer experiences torque proportional to current passed through it. If a
steady current i is passed through it the deflection of the coil is found to be 90°. Now the steady current
is switched off and a charge Q is suddenly passed through the coil. If the coil has N turns of area A each
and its moment of inertia is I about the axis it is going to rotate then the maximum angle through which
it deflects upon passing Q is :
(A)
5.
Q√
π NAB
2iI
(B) π Q
2
√
NAB
iI
(C)
π Q√
NAB
2iI
(D)
Q√
π NAB
iI
Two long conducting rectangular strips are placed parallel to each other at a distance d as shown. Strip A
is connected to a non-conducting spring of spring constant k. Strip B is fixed. Given ℓ >> b >> d. A
current i flows uniformly along the length ℓ of each strip and the currents in the strips are anti-parallel to
each other. The initial deformation in the spring keeps the system in static equilibrium. Now at t = 0, the
currents in both strips are halved and made parallel to each other suddenly. (Neglect gravity and assume
force on A is due to B and spring only and consider A and B as large sheets and neglect end effects)
(A)
the instantaneous force on strip A at t = 0+ is given by
5 μ 0 i2 ℓ
.
8b
3 μ 0 i2 ℓ
(B)
+
the instantaneous force on strip A at t = 0 is given by
.
8b
μ i2 ℓ
(C)
Elongation in spring at the instant t = 0+ is given by 0 .
2bk
μ i2 ℓ
(D)
Elongation in spring at the instant t = 0+ is given by 0
4bk
E-2/8
PHYSICS / ASSIGNMENT # 15
JEE (MAIN + ADVANCED) 2025
ENTHUSIAST COURSE
PHASE : TNAS & TMAS
ASSIGNMENT
SECTION-I (ii) : (Maximum Marks: 20)
Multiple Correct Answer Type 5 Q. [4 M (–1)]
6.
A tangent galvanometer is an old form of ammeter, consisting of an ordinary magnetic compas mounted
at the centre of a coil whose axis is horizontal and oriented along the east-west (Fig.). If there is no
current in the coil, the compass needle points north. The compass is in horizontal plane.
The horizontal component of earth's magnetic field is 5 × 10 –5 T. There are 100 turns in the coil, each
having a radius of 3.14 m. If the current in the coil is I, deflection in the compass needle is θ . Choose the
correct combination of I and θ .
7.
(A) I = 1A, θ = tan –1 (2.5) towards east.
(B) I = 2.5 A, θ = 45° towards east
(C) I =
(D) I = 4A, θ = tan−1
√
3A, θ = 30° towards east.
(
8
) towards east.
5
A wire frame ABCDEF is kept as shown in the figure. I is the current in the wire frame.
(A)
The direction of magnetic field at 'O' due to the wire frame will be along
(
−i^ − ^j
√
2
)
.
(B) The direction of magnetic field at P (0, a, 0) due to wire CD and DE will along −j^.
(C) The direction of magnetic field at Q (a, 0, 0) due to wire EF and CD will be along (−j^).
(D) The direction of magnetic field at P (0, a, 0) due to wire AF and CB will be along (−j^).
PHYSICS / ASSIGNMENT # 15
E-3/8
ASSIGNMENT
8.
An elastic string of force constant k and negligible length is attached to a point on a smooth horizontal
table. A particle of charge Q, mass m is attached to the other end. A vertical magnetic field B is present.
The particle is pulled out so that length of string becomes ℓ . It is now projected with a velocity v0 so that
the particle moves in a circular path about the other end. What is possible value of →v0 ? Take ℓ = 1m, m =
0.2kg, q = 1C, k = 30 N/m, B = 1T.
(A) 15k^ m/s
9.
JEE (MAIN + ADVANCED) 2025
ENTHUSIAST COURSE
PHASE : TNAS & TMAS
(B) 5k^ m/s
(C) −10k^ m/s
(D) −20k^ m/s
A circular coil C1 and a long straight wire C2 are kept such that straight wire is in a plane ⊥ to that of the
circular coil. Choose the correct statement(s) :
(A) If a steady current flows in C ,
→
→
2 ∮ B. d ℓ over C1 is zero.
(B)
∞
If a steady current flows in C1,
∫
−∞
→
→ d ℓ over C is zero.
B.
2
(C) If a steady current flows in C1, there are two points on C2 where B→ is perpendicular to C2.
(D)
E-4/8
∞
If a steady current flows in C1,
∫
−∞
→
→ d ℓ over C is non zero.
B.
2
PHYSICS / ASSIGNMENT # 15
ASSIGNMENT
10.
JEE (MAIN + ADVANCED) 2025
ENTHUSIAST COURSE
PHASE : TNAS & TMAS
Line BA & BC are intersecting at 'B' making angle π /3 at 'B'. Point A & C are at large distance from
point B. An infinite wire carrying current 'i' is kept perpendicular to plane containing line BA & BC and
intersect the plane at point 'P'. Current in the wire is into the plane of paper as shown in figure. Then
→
∫
→ d ℓ will be equal to:
B.
(A) − μ 0 i on line ABC
6
(C) 2 μ i on line AB
3
0
PHYSICS / ASSIGNMENT # 15
(B) μ 0 i on line ABC
6
(D) 5 μ i on line AB
0
12
E-5/8
JEE (MAIN + ADVANCED) 2025
ENTHUSIAST COURSE
PHASE : TNAS & TMAS
ASSIGNMENT
SECTION-I (iii) : (Maximum Marks: 9)
Linked Comprehension Type (Single option correct) 1 Para × 3 Q. [3(–1)]
Paragraph for Questions 11 - 13
A cylindrical capacitor with external radius R, internal radius R – d (d << R), length ℓ and mass M
hangs on an insulating cord in a region where there is a homogenous, vertical magnetic field of strength
B. It can rotate freely as a whole around its vertical axis, but is constrained, so that it can not move
horizontally. The capacitor is charged and there is a voltage difference V between its plates. (Neglect
gravity)
11.
Charge on capacitor is given by
(A) ∈ 0 2 π RlV
d
12.
(B) ∈ 0 π RlV
3d
(D) ∈ 0 π RlV
4d
If without being mechanically disturbed, the capacitor is discharged through an internal radial wire then
find maximum angular velocity of capacitor
(A) π ∈ 0 V Bl
(B) 2 π ∈ 0 V Bl
(C) 3 π ∈ 0 V BL
(D) 4 π ∈ 0 V BL
M
M
13.
2d
(C) ∈ 0 π RlV
M
M
Choose CORRECT statement
(A) When capacitor is discharged through radial wire then value of wmax depends on values of R
and d
(B) Value of wmax is independent of time dependence of discharge current
(C) Value of wmax is dependent on time dependence of discharge current
(D) Value of wmax cannot be calculated with the help of given data.
E-6/8
PHYSICS / ASSIGNMENT # 15
ASSIGNMENT
JEE (MAIN + ADVANCED) 2025
ENTHUSIAST COURSE
PHASE : TNAS & TMAS
SECTION-I (iv) : (Maximum Marks: 9)
Matching list Type (4 × 4 × 4)
1 Table × 3Q. [3M (–1)]
single options correct (three Columns and Four Rows)
Paragraph for Questions 14 - 16
14.
A square wire frame PQRS of side 1 m carrying a constant current of 4 A. The current is from P → Q
→ R → S. In column-I, we have certain configurations producing a magnetic field. In column-II, we
have mentioned the orientation of the loop and the plane of the loop. Column-III indicates the axis
about which the loop is free to rotate.
Column-I
Column-II
Column-III
Loop is kept in xy-plane
A long wire carrying a constant with sides parallel to x and yLine PQ is the axis of
(I) current of 1 A along positive z- (i) axis. Current in wire PQ is (P)
rotation.
axis
in direction of positive xaxis. Loop is in first quadrant.
Loop is kept in xz-plane
An infinite sheet kept in xy-plane
with sides parallel to x and zcarrying uniform current per unit
Line QR is the axis of
(II)
(ii) axis. Current in wire PQ is (Q)
length of 1 A/m flowing along xrotation.
in direction of positive zaxis
axis. Loop is in first quadrant.
A long solenoid carrying current Loop is kept in xy-plane
of 1 A and having 1000 turns/m. with sides parallel to x and y- The loop is free
(III) The axis of solenoid is z-axis. (iii) axis. Current in wire PQ is (R) to rotate about any
The loop is entirely inside in direction of positive x-axis. axis.
the solenoid.
Loop is in second quadrant.
Loop is kept in xz-plane
A small magnetic dipole of
with sides parallel to x and zdipole moment 4 Am at the
The diagonal PR
(IV)
(iv) axis. Current in wire PQ is (S)
origin such that its dipole
is the axis of rotation
in direction of positive zmoment is along z-axis.
axis. Loop is in second quadrant.
In which of the following cases, the loop does not rotate at all?
(A) (I) (i) (S)
15.
(C) (III) (ii) (P)
(D) (IV) (ii) (Q)
In which of the following cases, the loop experiences a net force?
(A) (I) (ii) (R)
16.
(B) (II) (iv) (R)
(B) (II) (i) (R)
(C) (III) (i) (R)
(D) (II) (iii) (R)
In which of the following cases, the loop starts rotating?
(A) (II) (i) (P)
PHYSICS / ASSIGNMENT # 15
(B) (II) (iii) (Q)
(C) (III) (i) (P)
(D) (III) (iii) (P)
E-7/8
JEE (MAIN + ADVANCED) 2025
ENTHUSIAST COURSE
PHASE : TNAS & TMAS
ASSIGNMENT
SECTION-III : (Maximum Marks: 9)
Numerical Grid Type (Ranging from 0 to 9) 3 Q.[3(-0)]
1.
A thin glass rod of radius R and length L carries a uniform surface charge σ . It is set spinning about its
axis, at an angular velocity ω . The magnetic field at a distance S >> R from the axis, in the x-y plane is
μ 0 ω σ LR α
, where α , β & γ are integers. Fill the value of α + β + γ in OMR sheet.
γ
2
2 2
given by
β [S 2 + ( L2 ) ]
2.
An infinite uniform current carrying wire is kept along z-axis, carrrying current I0 in the direction of the
positive z-axis. OABCDEFG represents a circle (where all the points are equally spaced), whose centre
at point (4m, 0 m) and radius 4 m as shown in the figure. If
value of k.
3.
∫
DEF
→ d →ℓ = μ 0 I0 in S.I. unit, then find the
B.
k
An infinite current carrying conductor, parallel to z-axis is situated at point P as shown in the figure.
B
Value of
∫
→ . d→ℓ is given by α μ 0 i , then fill the value of α in OMR sheet ?
B
96
A
E-8/8
PHYSICS / ASSIGNMENT # 15