1
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
At the center of a fixed large circular coil of radius R, a much smaller circular coil of radius r is placed. The two coils are concentric and are in the same plane. The larger coil carries a current I. The smaller coil is set to rotate with a constant angular velocity $$\omega$$ about an axis along their common diameter. Calculate the emf induced in their smaller coil after a time t of its start of rotation.
A
$${{{\mu _o}{\rm I}} \over {2\,R}}$$ $$\omega$$ $$\pi$$ r2 sin$$\omega$$ t
B
$${{{\mu _o}{\rm I}} \over {4\,R}}$$ $$\omega$$ $$\pi$$ r2 sin$$\omega$$ t
C
$${{{\mu _o}{\rm I}} \over {4\,R}}$$ $$\omega$$ r2 sin$$\omega$$ t
D
$${{{\mu _o}{\rm I}} \over {2\,R}}$$ $$\omega$$ r2 sin$$\omega$$ t
2
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
A plane polarized monochromatic EM wave is traveling in vacuum along z direction such that at t = t1 it is found that the electric field is zero at a spatial point z1. The next zero that occurs in its neighbourhood is at z2. The frequency of the electroagnetic wave is :
A
$${{3 \times {{10}^8}} \over {\left| {{z_2} - {z_1}} \right|}}$$
B
$${{1.5 \times {{10}^8}} \over {\left| {{z_2} - {z_1}} \right|}}$$
C
$${{6 \times {{10}^8}} \over {\left| {{z_2} - {z_1}} \right|}}$$
D
$${1 \over {{t_1} + {{\left| {{z_2} - {z_1}} \right|} \over {3 \times {{10}^8}}}}}$$
3
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
A convergent doublet of separated lenses, corrected for spherical aberration, has resultant focal length of 10 cm. The separation between the two lenses is $$2$$ cm. The focal lengths of the component lenses are :
A
10 cm, 12 cm
B
12 cm, 14 cm
C
16 cm, 18 cm
D
18 cm, 20cm
4
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
If the de Broglie wavelengths associated with a proton and an $$\alpha$$-particle are equal, then the ratio of velocities of the proton and the $$\alpha$$-particle will be :
A
4 : 1
B
2 : 1
C
1 : 2
D
1 : 4
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