1
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Shown in the figure is a shell made of a conductor. It has inner radius a and outer radius b, and carries charge Q. At its centre is a dipole $$\overrightarrow P $$ as shown. In this case : JEE Main 2019 (Online) 12th April Morning Slot Physics - Electrostatics Question 186 English
A
surface charge density on the inner surface is uniform and equal to $${{\left( {Q/2} \right)} \over {4\pi {a^2}}}$$
B
surface charge density on the inner surface of the shell is zero everywhere
C
surface charge density on the outer surface depends on $$\left| {\overrightarrow P } \right|$$
D
electric field outside the shell is the same as that of a point charge at the centre of the shell
2
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A circular disc of radius b has a hole of radius a at its centre (see figure). If the mass per unit area of the disc varies as $$\left( {{{{\sigma _0}} \over r}} \right)$$ , then the radius of gyration of the disc about its axis passing through the centre is: JEE Main 2019 (Online) 12th April Morning Slot Physics - Rotational Motion Question 161 English
A
$$\sqrt {{{{a^2} + {b^2} + ab} \over 2}} $$
B
$$\sqrt {{{a + b} \over 3}} $$
C
$$\sqrt {{{{a^2} + {b^2} + ab} \over 3}} $$
D
$$\sqrt {{{a + b} \over 2}} $$
3
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
An excited He+ ion emits two photons in succession, with wavelengths 108.5 nm and 30.4 nm, in making a transition to ground state. The quantum number n, corresponding to its initial excited state is (for photon of wavelength $$\lambda $$, energy $$E = {{1240\,eV} \over {\lambda (in\,nm)}}$$) :
A
n = 4
B
n = 7
C
n = 5
D
n = 6
4
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A progressive wave travelling along the positive x-direction is represented by y(x,t) = Asin(kx – $$\omega $$t + $$\phi $$). Its snapshot at t = 0 is given in the figure. JEE Main 2019 (Online) 12th April Morning Slot Physics - Waves Question 93 English
For this wave, the phase $$\phi $$ is :
A
$${\pi \over 2}$$
B
$$\pi $$
C
0
D
$$ - {\pi \over 2}$$
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