1
WB JEE 2022
MCQ (Single Correct Answer)
+1
-0.25
Change Language

WB JEE 2022 Physics - Magnetism Question 5 English

Two infinite line-charges parallel to each other are moving with a constant velocity v in the same direction as shown in the figure. The separation between two line-charges is d. The magnetic attraction balances the electric repulsion when, [ c = speed of light in free space ]

A
$$v = \sqrt 2 c$$
B
$$v = {c \over {\sqrt 2 }}$$
C
$$v = c$$
D
$$v = {c \over 2}$$
2
WB JEE 2022
MCQ (Single Correct Answer)
+1
-0.25
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An electron revolves around the nucleus in a circular path with angular momentum $$\overrightarrow L $$. A uniform magnetic field $$\overrightarrow B $$ is applied perpendicular to the plane of its orbit. If the electron experiences a torque $$\overrightarrow T $$, then

A
$$\overrightarrow T ||\overrightarrow L $$
B
$$\overrightarrow T $$ is anti-parallel to $$\overrightarrow L $$
C
$$\overrightarrow T \,.\,\overrightarrow L = 0$$
D
Angle between $$\overrightarrow T $$ and $$\overrightarrow L $$ is $$45^\circ $$
3
WB JEE 2022
MCQ (Single Correct Answer)
+1
-0.25
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A straight wire is placed in a magnetic field that varies with distance x from origin as $$\overrightarrow B = {B_0}\left( {2 - {x \over a}} \right)\widehat k$$. Ends of wire are at (a, 0) and (2a, 0) and it carries a current I. If force on wire is $$\overrightarrow F = I{B_0}\left( {{{ka} \over 2}} \right)\widehat j$$, then value of k is

A
1
B
5
C
$$-$$1
D
$${1 \over 2}$$
4
WB JEE 2022
MCQ (Single Correct Answer)
+2
-0.5
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A horizontal semi-circular wire of radius r is connected to a battery through two similar springs X and Y to an electric cell, which sends current I through it. A vertically downward uniform magnetic field B is applied on the wire, as shown in the figure. What is the force acting on each spring?

WB JEE 2022 Physics - Magnetism Question 8 English

A
$$2\pi rBI$$
B
$${1 \over 2}\pi rBI$$
C
$$BIr$$
D
$$2BIr$$
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