WB JEE 2022 | Magnetism Question 8 | Physics

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

$$-$$1

$${1 \over 2}$$

WB JEE 2022

MCQ (Single Correct Answer)

-0.5

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 10 English

$$2\pi rBI$$

$${1 \over 2}\pi rBI$$

$$BIr$$

$$2BIr$$

WB JEE 2021

MCQ (Single Correct Answer)

-0.25

WB JEE 2021 Physics - Magnetism Question 13 English

Consider two infinitely long wires parallel to Z-axis carrying same current I in the positive z-direction. One wire passes through the point L at coordinates ($$-$$1, +1) and the other wire passes through the point M at coordinates ($$-$$1, $$-$$1). The resultant magnetic field at the origin O will be

$${{{\mu _0}I} \over {2\sqrt 2 \pi }}\widehat j$$

$${{{\mu _0}I} \over {2\pi }}\widehat j$$

$${{{\mu _0}I} \over {2\sqrt 2 \pi }}\widehat i$$

$${{{\mu _0}I} \over {4\pi }}\widehat i$$

WB JEE 2021

MCQ (Single Correct Answer)

-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

m = 2, n = 2

m = 2, n = 3

m = 3, n = 2

m = 3, n = 3

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