1
JEE Main 2020 (Online) 5th September Morning Slot
+4
-1
An electron is constrained to move along the y-axis with a speed of 0.1 c (c is the speed of light) in the presence of electromagnetic wave, whose electric field is
$$\overrightarrow E = 30\widehat j\sin \left( {1.5 \times {{10}^7}t - 5 \times {{10}^{ - 2}}x} \right)$$ V/m.
The maximum magnetic force experienced by the electron will be :
(given c = 3 $$\times$$ 108 ms–1 and electron charge = 1.6 $$\times$$ 10–19 C)
A
4.8 $$\times$$ 10–19 N
B
2.4 $$\times$$ 10–18 N
C
3.2 $$\times$$ 10–18 N
D
1.6 $$\times$$ 10–18 N
2
JEE Main 2020 (Online) 5th September Morning Slot
+4
-1
A square loop of side 2$$a$$, and carrying current I, is kept in XZ plane with its centre at origin. A long wire carrying the same current I is placed parallel to the z-axis and passing through the point (0, b, 0), (b >> a). The magnitude of the torque on the loop about zaxis is given by :
A
$${{2{\mu _0}{I^2}{a^2}} \over {\pi b}}$$
B
$${{{\mu _0}{I^2}{a^2}} \over {2\pi b}}$$
C
$${{{\mu _0}{I^2}{a^3}} \over {2\pi {b^2}}}$$
D
$${{2{\mu _0}{I^2}{a^3}} \over {\pi {b^2}}}$$
3
JEE Main 2020 (Online) 4th September Evening Slot
+4
-1
A circular coil has moment of inertia 0.8 kg m2 around any diameter and is carrying current to produce a magnetic moment of 20 Am2 . The coil is kept initially in a vertical position and it can rotate freely around a horizontal diameter. When a uniform magnetic field of 4 T is applied along the vertical,it starts rotating around its horizontal diameter. The angular speed the coil acquires after rotating by 60o will be:
A
10 $$\pi$$ rad s–1
B
20 $$\pi$$ rad s–1
C
$$10{\left( 3 \right)^{1/4}}$$ rad s–1
D
4
JEE Main 2020 (Online) 4th September Evening Slot
+4
-1
The electric field of a plane electromagnetic wave is given by
$$\overrightarrow E = {E_0}\left( {\widehat x + \widehat y} \right)\sin \left( {kz - \omega t} \right)$$
Its magnetic field will be given by :
A
$${{{E_0}} \over c}\left( {\widehat x + \widehat y} \right)\sin \left( {kz - \omega t} \right)$$
B
$${{{E_0}} \over c}\left( {\widehat x - \widehat y} \right)\sin \left( {kz - \omega t} \right)$$
C
$${{{E_0}} \over c}\left( {\widehat x - \widehat y} \right)\cos \left( {kz - \omega t} \right)$$
D
$${{{E_0}} \over c}\left( { - \widehat x + \widehat y} \right)\sin \left( {kz - \omega t} \right)$$
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Physics
Mechanics
Electricity
Optics
Modern Physics
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