1
JEE Main 2021 (Online) 17th March Evening Shift
+4
-1
A hairpin like shape as shown in figure is made by bending a long current carrying wire. What is the magnitude of a magnetic field at point P which lies on the centre of the semicircle?

A
$${{{\mu _0}I} \over {4\pi r}}(2 - \pi )$$
B
$${{{\mu _0}I} \over {2\pi r}}(2 - \pi )$$
C
$${{{\mu _0}I} \over {4\pi r}}(2 + \pi )$$
D
$${{{\mu _0}I} \over {2\pi r}}(2 + \pi )$$
2
JEE Main 2021 (Online) 17th March Morning Shift
+4
-1
A solenoid of 1000 turns per metre has a core with relative permeability 500. Insulated windings of the solenoid carry an electric current of 5A. The magnetic flux density produced by the solenoid is : (permeability of free space = 4$$\pi$$ $$\times$$ 10$$-$$7 H/m)
A
$$\pi$$T
B
2 $$\times$$ 10$$-$$3$$\pi$$ T
C
10$$-$$4$$\pi$$ T
D
$${\pi \over 5}$$ T
3
JEE Main 2021 (Online) 16th March Evening Shift
+4
-1
A charge Q is moving $$\overrightarrow {dl}$$ distance in the magnetic field $$\overrightarrow {B}$$. Find the value of work done by $$\overrightarrow {B}$$.
A
Zero
B
$$-$$1
C
Infinite
D
1
4
JEE Main 2021 (Online) 16th March Evening Shift
+4
-1
The magnetic field in a region is given by $$\overrightarrow B = {B_o}\left( {{x \over a}} \right)\widehat k$$. A square loop of side d is placed with its edges along the x and y axes. The loop is moved with a constant velocity $$\overrightarrow v$$ = v0$$\widehat i$$. The emf induced in the loop is :

A
$${{{B_o}{v_o}{d^2}} \over {2a}}$$
B
$${{{B_o}v_o^2d} \over {2a}}$$
C
$${{{B_o}{v_o}d} \over {2a}}$$
D
$${{{B_o}{v_o}{d^2}} \over a}$$
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