1
JEE Main 2019 (Online) 9th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The magnetic field of a plane electromagnetic wave is given by :
$$$\overline B = {B_0}\widehat i\left[ {\cos (kz - \omega t)} \right] + {B_i}\widehat j\cos (kz + \omega t)$$$ B0 = 3 × 10–5 T and B1 = 2 × 10–6 T.
The rms value of the force experienced by a stationary charge Q = 10–4 C at z = 0 is closest to :
A
0.6 N
B
0.9 N
C
3 × 10–2 N
D
0.1 N
2
JEE Main 2019 (Online) 9th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A uniform cable of mass 'M' and length 'L' is placed on a horizontal surface such that its (1/n)th part is hanging below the edge of the surface. To lift the hanging part of the cable upto the surface, the work done should be :
A
$${{2MgL} \over {{n^2}}}$$
B
nMgL
C
$${{MgL} \over {2{n^2}}}$$
D
$${{MgL} \over {{n^2}}}$$
3
JEE Main 2019 (Online) 9th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A stationary horizontal disc is free to rotate about its axis. When a torque is applied on it, its kinetic energy as a function of $$\theta $$, where $$\theta $$ is the angle by which it has rotated, is given as k$$\theta $$2. If its moment of inertia is I then the angular acceleration of the disc is :
A
$${k \over {4I}}\theta $$
B
$${k \over {I}}\theta $$
C
$${k \over {2I}}\theta $$
D
$${2k \over {I}}\theta $$
4
JEE Main 2019 (Online) 9th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A string is clamped at both the ends and it is vibrating in its 4th harmonic. The equation of the stationary wave is Y = 0.3 sin(0.157x) cos(200pt). The length of the string is : (All quantities are in SI units.)
A
60 m
B
20 m
C
80 m
D
40 m
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