1
JEE Main 2021 (Online) 18th March Evening Shift
+4
-1
A proton and an $$\alpha$$-particle, having kinetic energies Kp and K$$\alpha$$ respectively, enter into a magnetic field at right angles.

The ratio of the radii of trajectory of proton to that of $$\alpha$$-particle is 2 : 1. The ratio of Kp : K$$\alpha$$ is :
A
8 : 1
B
4 : 1
C
1 : 8
D
1 : 4
2
JEE Main 2021 (Online) 18th March Morning Shift
+4
-1
Four identical long solenoids A, B, C and D are connected to each other as shown in the figure. If the magnetic field at the center of A is 3T, the field at the center of C would be : (Assume that the magnetic field is confined with in the volume of respective solenoid).

A
12T
B
6T
C
9T
D
1T
3
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.
4
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
$${{{\mu _0}I} \over {2\pi r}}(2 + \pi )$$
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