1
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
$${{{\mu _0}I} \over {\pi a}}2\sqrt 2 (\sqrt 2$$ - $$1)$$
2
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
3
WB JEE 2019
+1
-0.25
To which of the following quantities, the radius of the circular path of a charged particle moving at right angles to a uniform magnetic field is directly proportional?
A
energy of the particle
B
magnetic field
C
charge of the particle
D
momentum of the particle
4
WB JEE 2019
+1
-0.25
An electric current 'I' enters and leaves a uniform circular wire of radius r through diametrically opposite points. A particle carrying a charge q moves along the axis of the circular wire with speed v. What is the magnetic force experienced by the particle when it passes through the centre of the circle?
A
$$qv{{{\mu _0}i} \over a}$$
B
$$qv{{{\mu _0}i} \over {2a}}$$
C
$$qv{{{\mu _0}i} \over {2\pi a}}$$
D
Zero
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