1
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
A particle of mass m and charge q has an initial velocity $$\overrightarrow v = {v_0}\widehat j$$ . If an electric field $$\overrightarrow E = {E_0}\widehat i$$ and magnetic field $$\overrightarrow B = {B_0}\widehat i$$ act on the particle, its speed will double after a time:
A
$${{3m{v_0}} \over {q{E_0}}}$$
B
$${{\sqrt 2 m{v_0}} \over {q{E_0}}}$$
C
$${{\sqrt 3 m{v_0}} \over {q{E_0}}}$$
D
$${{2m{v_0}} \over {q{E_0}}}$$
2
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
The figure gives experimentally measured B vs H variation in a ferromagnetic material. The retentivity, coercivity and saturation, respectively, of the material are :
A
1.0 T, 50A/m and 1.5 T
B
1.5 T, 50 A/m and 1.0 T
C
1.5 T, 50 A/m and 1.0 T
D
150 A/m, 1.0 T and 1.5 T
3
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
A planar loop of wire rotates in a uniform magnetic field. Initially at t = 0, the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of 10 s about an axis in its plane then the magnitude of induced emf will be maximum and minimum, respectively at :
A
2.5 s and 7.5 s
B
5.0 s and 10.0 s
C
5.0 s and 7.5 s
D
2.5 s and 5.0 s
4
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
The electric field of a plane electromagnetic wave is given by
$$\overrightarrow E = {E_0}{{\widehat i + \widehat j} \over {\sqrt 2 }}\cos \left( {kz + \omega t} \right)$$

At t = 0, a positively charged particle is at the point (x, y, z) = $$\left( {0,0,{\pi \over k}} \right)$$.
If its instantaneous velocity at (t = 0) is $${v_0}\widehat k$$ , the force acting on it due to the wave is :
A
parallel to $$\widehat k$$
B
parallel to $${{\widehat i + \widehat j} \over {\sqrt 2 }}$$
C
antiparallel to $${{\widehat i + \widehat j} \over {\sqrt 2 }}$$
D
zero
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