1
JEE Main 2021 (Online) 18th March Morning Shift
+4
-1
A loop of flexible wire of irregular shape carrying current is placed in an external magnetic field. Identify the effect of the field on the wire.
A
Loop assumes circular shape with its plane normal to the field.
B
Loop assumes circular shape with its plane parallel to the field.
C
Wire gets stretched to become straight.
D
Shape of the loop remains unchanged.
2
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
$${{{\mu _0}I} \over {2\pi r}}(2 + \pi )$$
3
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
4
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
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