1
JEE Main 2020 (Online) 9th January Morning Slot
+4
-1
A long, straight wire of radius a carries a current distributed uniformly over its cross-section. The ratio of the magnetic fields due to the wire at distance $${a \over 3}$$ and 2$$a$$, respectively from the axis of the wire is :
A
2
B
$${1 \over 2}$$
C
$${3 \over 2}$$
D
$${2 \over 3}$$
2
JEE Main 2020 (Online) 9th January Morning Slot
+4
-1
The electric fields of two plane electromagnetic plane waves in vacuum are given by
$$\overrightarrow {{E_1}} = {E_0}\widehat j\cos \left( {\omega t - kx} \right)$$ and
$$\overrightarrow {{E_2}} = {E_0}\widehat k\cos \left( {\omega t - ky} \right)$$
At t = 0, a particle of charge q is at origin with
a velocity $$\overrightarrow v = 0.8c\widehat j$$ (c is the speed of light in vacuum). The instantaneous force experienced by the particle is :
A
$${E_0}q\left( {0.8\widehat i - \widehat j + 0.4\widehat k} \right)$$
B
$${E_0}q\left( { - 0.8\widehat i + \widehat j + \widehat k} \right)$$
C
$${E_0}q\left( {0.8\widehat i + \widehat j + 0.2\widehat k} \right)$$
D
$${E_0}q\left( {0.4\widehat i - 3\widehat j + 0.8\widehat k} \right)$$
3
JEE Main 2020 (Online) 9th January Morning Slot
+4
-1
A charged particle of mass 'm' and charge 'q' moving under the influence of uniform electric field $$E\overrightarrow i$$ and a uniform magnetic field $$B\overrightarrow k$$ follows a trajectory from point P to Q as shown in figure. The velocities at P and Q are respectively, $$v\overrightarrow i$$ and $$- 2v\overrightarrow j$$ . Then which of the following statements (A, B, C, D) are the correct ?
(Trajectory shown is schematic and not to scale) :
(A) E = $${3 \over 4}\left( {{{m{v^2}} \over {qa}}} \right)$$

(B) Rate of work done by the electric field at P is $${3 \over 4}\left( {{{m{v^3}} \over a}} \right)$$

(C) Rate of work done by both the fields at Q is zero

(D) The difference between the magnitude of angular momentum of the particle at P and Q is 2mav.
A
(A), (B), (C), (D)
B
(A), (B), (C)
C
(A), (C), (D)
D
(B), (C), (D)
4
JEE Main 2020 (Online) 8th January Evening Slot
+4
-1
A plane electromagnetic wave of frequency 25 GHz is propagating in vacuum along the z-direction. At a particular point in space and time, the magnetic field is given by $$\overrightarrow B = 5 \times {10^{ - 8}}\widehat jT$$. The corresponding electric field $$\overrightarrow E$$ is (speed of light c = 3 × 108 ms–1)
A
15 $$\widehat i$$V / m
B
-15 $$\widehat i$$V / m
C
1.66 × 10–16 $$\widehat i$$V / m
D
-1.66 × 10–16 $$\widehat i$$V / m
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