1
JEE Main 2021 (Online) 24th February Evening Shift
+4
-1
A soft ferromagnetic material is placed in an external magnetic field. The magnetic domains :
A
may increase or decrease in size and change its orientation.
B
increase in size but no change in orientation.
C
decrease in size and changes orientation.
D
have no relation with external magnetic field.
2
JEE Main 2020 (Online) 6th September Evening Slot
+4
-1
For a plane electromagnetic wave, the magnetic field at a point x and time t is

$$\overrightarrow B \left( {x,t} \right)$$ = $$\left[ {1.2 \times {{10}^{ - 7}}\sin \left( {0.5 \times {{10}^3}x + 1.5 \times {{10}^{11}}t} \right)\widehat k} \right]$$ T

The instantaneous electric field $$\overrightarrow E$$ corresponding to $$\overrightarrow B$$ is :
(speed of light c = 3 × 108 ms–1)
A
$$\overrightarrow E \left( {x,t} \right) = \left[ {36\sin \left( {1 \times {{10}^3}x + 1.5 \times {{10}^{11}}t} \right)\widehat i} \right]$$ $${V \over m}$$
B
$$\overrightarrow E \left( {x,t} \right) = \left[ {36\sin \left( {0.5 \times {{10}^3}x + 1.5 \times {{10}^{11}}t} \right)\widehat k} \right]{V \over m}$$
C
$$\overrightarrow E \left( {x,t} \right) = \left[ {36\sin \left( {1 \times {{10}^3}x + 0.5 \times {{10}^{11}}t} \right)\widehat j} \right]{V \over m}$$
D
$$\overrightarrow E \left( {x,t} \right) = \left[ { - 36\sin \left( {0.5 \times {{10}^3}x + 1.5 \times {{10}^{11}}t} \right)\widehat j} \right]{V \over m}$$
3
JEE Main 2020 (Online) 6th September Evening Slot
+4
-1
A charged particle going around in a circle can be considered to be a current loop. A particle of mass m carrying charge q is moving in a plane with speed v under the influence of magnetic field $$\overrightarrow B$$. The magnetic moment of this moving particle:
A
$${{m{v^2}\overrightarrow B } \over {2{B^2}}}$$
B
-$${{m{v^2}\overrightarrow B } \over {2{B^2}}}$$
C
-$${{m{v^2}\overrightarrow B } \over {{B^2}}}$$
D
-$${{m{v^2}\overrightarrow B } \over {2\pi {B^2}}}$$
4
JEE Main 2020 (Online) 6th September Evening Slot
+4
-1
A square loop of side 2$$a$$ and carrying current I is kept in xz plane with its centre at origin. A long wire carrying the same current I is placed parallel to z-axis and passing through point (0, b, 0), (b >> a). The magnitude of torque on the loop about z-axis will be :
A
$${{2{\mu _0}{I^2}{a^2}} \over {\pi b}}$$
B
$${{2{\mu _0}{I^2}{a^2}b} \over {\pi \left( {{a^2} + {b^2}} \right)}}$$
C
$${{{\mu _0}{I^2}{a^2}b} \over {2\pi \left( {{a^2} + {b^2}} \right)}}$$
D
$${{{\mu _0}{I^2}{a^2}} \over {2\pi b}}$$
JEE Main Subjects
Physics
Mechanics
Electricity
Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
Mathematics
Algebra
Trigonometry
Coordinate Geometry
Calculus
EXAM MAP
Joint Entrance Examination