JEE Main 2021 (Online) 24th February Evening Shift | Magnetics Question 125 | Physics

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JEE Main 2021 (Online) 24th February Evening Shift

MCQ (Single Correct Answer)

-1

A soft ferromagnetic material is placed in an external magnetic field. The magnetic domains :

may increase or decrease in size and change its orientation.

increase in size but no change in orientation.

decrease in size and changes orientation.

have no relation with external magnetic field.

JEE Main 2020 (Online) 6th September Evening Slot

MCQ (Single Correct Answer)

-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)

$$\overrightarrow E \left( {x,t} \right) = \left[ {36\sin \left( {1 \times {{10}^3}x + 1.5 \times {{10}^{11}}t} \right)\widehat i} \right]$$ $${V \over m}$$

$$\overrightarrow E \left( {x,t} \right) = \left[ {36\sin \left( {0.5 \times {{10}^3}x + 1.5 \times {{10}^{11}}t} \right)\widehat k} \right]{V \over m}$$

$$\overrightarrow E \left( {x,t} \right) = \left[ {36\sin \left( {1 \times {{10}^3}x + 0.5 \times {{10}^{11}}t} \right)\widehat j} \right]{V \over m}$$

$$\overrightarrow E \left( {x,t} \right) = \left[ { - 36\sin \left( {0.5 \times {{10}^3}x + 1.5 \times {{10}^{11}}t} \right)\widehat j} \right]{V \over m}$$

JEE Main 2020 (Online) 6th September Evening Slot

MCQ (Single Correct Answer)

-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:

$${{m{v^2}\overrightarrow B } \over {2{B^2}}}$$

-$${{m{v^2}\overrightarrow B } \over {2{B^2}}}$$

-$${{m{v^2}\overrightarrow B } \over {{B^2}}}$$

-$${{m{v^2}\overrightarrow B } \over {2\pi {B^2}}}$$

JEE Main 2020 (Online) 6th September Evening Slot

MCQ (Single Correct Answer)

-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 :

$${{2{\mu _0}{I^2}{a^2}} \over {\pi b}}$$

$${{2{\mu _0}{I^2}{a^2}b} \over {\pi \left( {{a^2} + {b^2}} \right)}}$$

$${{{\mu _0}{I^2}{a^2}b} \over {2\pi \left( {{a^2} + {b^2}} \right)}}$$

$${{{\mu _0}{I^2}{a^2}} \over {2\pi b}}$$

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