1
JEE Main 2019 (Online) 12th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A plane electromagnetic wave having a frequency v = 23.9 GHz propagates along the positive z-direction in free space. The peak value of the Electric Field is 60 V/m. Which among the following is the acceptable magnetic field component in the electromagnetic wave ?
A
$$\overrightarrow B $$ = 2 × 10–7 sin(1.5 × 102 x + 0.5 × 1011t) $$\widehat j$$
B
$$\overrightarrow B $$ = 60 sin(0.5 × 103x + 0.5 × 1011t) $$\widehat k$$
C
$$\overrightarrow B $$ = 2 × 10–7 sin(0.5 × 103 z + 1.5 × 1011t) $$\widehat i$$
D
$$\overrightarrow B $$ = 2 × 10–7 sin(0.5 × 103 z - 1.5 × 1011t) $$\widehat i$$
2
JEE Main 2019 (Online) 12th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A diatomic gas with rigid molecules does 10 J of work when expanded at constant pressure. What would be the heat energy absorbed by the gas, in this process ?
A
35 J
B
30 J
C
25 J
D
40 J
3
JEE Main 2019 (Online) 12th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A uniform cylindrical rod of length L and radius r, is made from a material whose Young’s modulus of Elasticity equals Y. When this rod is heated by temperature T and simultaneously subjected to a net longitudinal compressional force F, its length remains unchanged. The coefficient of volume expansion, of the material of the rod, is (nearly) equal to :
A
$${{3F} \over {\left( {\pi {r^2}YT} \right)}}$$
B
$${{6F} \over {\left( {\pi {r^2}YT} \right)}}$$
C
$${F \over {\left( {3\pi {r^2}YT} \right)}}$$
D
$${9F\left( {\pi {r^2}YT} \right)}$$
4
JEE Main 2019 (Online) 12th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A smooth wire of length 2$$\pi $$r is bent into a circle and kept in a vertical plane. A bead can slide smoothly on the wire. When the circle is rotating with angular speed $$\omega $$ about the vertical diameter AB, as shown in figure, the bead is at rest with respect to the circular ring at position P as shown. Then the value of $$\omega $$2 is equal to - JEE Main 2019 (Online) 12th April Evening Slot Physics - Circular Motion Question 51 English
A
$${{\sqrt 3 g} \over {2r}}$$
B
$${{2g} \over {\left( {r\sqrt 3 } \right)}}$$
C
$${{\left( {g\sqrt 3 } \right)} \over r}$$
D
$${{2g} \over r}$$
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