1
JEE Main 2021 (Online) 26th August Evening Shift
+4
-1
A light beam is described by $$E = 800\sin \omega \left( {t - {x \over c}} \right)$$. An electron is allowed to move normal to the propagation of light beam with a speed of 3 $$\times$$ 107 ms$$-$$1. What is the maximum magnetic force exerted on the electron?
A
1.28 $$\times$$ 10$$-$$18 N
B
1.28 $$\times$$ 10$$-$$21 N
C
12.8 $$\times$$ 10$$-$$17 N
D
12.8 $$\times$$ 10$$-$$18 N
2
JEE Main 2021 (Online) 26th August Morning Shift
+4
-1
The fractional change in the magnetic field intensity at a distance 'r' from centre on the axis of current carrying coil of radius 'a' to the magnetic field intensity at the centre of the same coil is : (Take r < a)
A
$${3 \over 2}{{{a^2}} \over {{r^2}}}$$
B
$${2 \over 3}{{{a^2}} \over {{r^2}}}$$
C
$${2 \over 3}{{{r^2}} \over {{a^2}}}$$
D
$${3 \over 2}{{{r^2}} \over {{a^2}}}$$
3
JEE Main 2021 (Online) 27th July Evening Shift
+4
-1
Figure A and B shown to long straight wires of circular cross-section (a and b with a < b), carrying current I which is uniformly distributed across the cross-section. The magnitude of magnetic field B varies with radius r and can be represented as :

A
B
C
D
4
JEE Main 2021 (Online) 25th July Evening Shift
+4
-1
Two ions having same mass have charges in the ratio 1 : 2. They are projected normally in a uniform magnetic field with their speeds in the ratio 2 : 3. The ratio of the radii of their circular trajectories is :
A
1 : 4
B
4 : 3
C
3 : 1
D
2 : 3
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