1
WB JEE 2021
+1
-0.25 A thin charged rod is bent into the shape of a small circle of radius R, the charge per unit length of the rod being $$\lambda$$. The circle is rotated about its axis with a time period T and it is found the magnetic field at a distance d away (d >> R) from the centre and on the axis, varies as $$R^m \over d^n$$. The values of m and n respectively are
A
m = 2, n = 2
B
m = 2, n = 3
C
m = 3, n = 2
D
m = 3, n = 3
2
WB JEE 2021
+1
-0.25  For two types of magnetic materials A and B, variation of $$1\over\chi$$ ($$\chi$$ : susceptibility) versus temperature T is shown in the figure. Then,
A
A is diamagnetic and B is paramagnetic.
B
A is feromagnetic and B is diamagnetic.
C
A is paramagnetic and B is feromagnetic.
D
A is paramagnetic and B is diamagnetic.
3
WB JEE 2020
+1
-0.25  As shown in the figure, a single conducting wire is bent to form a loop in the form of a circle of radius r concentrically inside a square of side a, where a : r = 8 : $$\pi$$. A battery B drives a current through the wire. If the battery B and the gap G are of negligible sizes, determine the strength of magnetic field at the common centre O.
A
$${{{\mu _0}I} \over {2\pi a}}\sqrt 2 (\sqrt 2 - 1)$$
B
$${{{\mu _0}I} \over {2\pi a}} (\sqrt 2 + 1)$$
C
$${{{\mu _0}I} \over {\pi a}}2\sqrt 2 (\sqrt 2 + 1)$$
D
$${{{\mu _0}I} \over {\pi a}}2\sqrt 2 (\sqrt 2$$ - $$1)$$
4
WB JEE 2020
+1
-0.25  As shown in the figure, a wire is bent to form a D-shaped closed loop, carrying current I, where the curved part is a semi-circle of radius R. The loop is placed in a uniform magnetic field B, which is directed into the plane of the paper. The magnetic force felt by the closed loop is
A
zero
B
IRB
C
2IRB
D
$${1 \over 2}$$ IRB
WB JEE Subjects
Physics
Mechanics
Electricity
Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
Mathematics
Algebra
Trigonometry
Coordinate Geometry
Calculus
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