1
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A thin ring of 10 cm radius carries a uniformly distributed charge. The ring rotates at a constant angular speed of 40 $$\pi $$ rad s–1 about its axis, perpendicular to its plane. If the magnetic field at its centre is 3.8 × 10–9 T, then the charge carried by the ring is close to ($$\mu $$0 = 4$$\pi $$ × 10–7 N/A2 ).
A
7 × 10–6 C
B
4 × 10–5 C
C
2 × 10–6 C
D
3 × 10–5 C
2
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 167 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
3
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A shell is fired from a fixed artillery gun with an initial speed u such that it hits the target on the ground at a distance R from it. If t1 and t2 are the values of the time taken by it to hit the target in two possible ways, the product t1t2 is -
A
$${{2R} \over g}$$
B
$${R \over g}$$
C
$${R \over {2g}}$$
D
$${R \over {4g}}$$
4
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 147 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
$$\sqrt {{{a + b} \over 2}} $$
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