1
JEE Main 2020 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
An electron gun is placed inside a long solenoid of radius R on its axis. The solenoid has n turns/length and carries a current I. The electron gun shoots an electron along the radius of the solenoid with speed v. If the electron does not hit the surface of the solenoid, maximum possible value of v is (all symbols have their standard meaning) : JEE Main 2020 (Online) 9th January Evening Slot Physics - Magnetic Effect of Current Question 111 English
A
$${{e{\mu _0}nIR} \over {4m}}$$
B
$${{e{\mu _0}nIR} \over m}$$
C
$${{e{\mu _0}nIR} \over {2m}}$$
D
$${{2e{\mu _0}nIR} \over m}$$
2
JEE Main 2020 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A small circular loop of conducting wire has radius a and carries current I. It is placed in a uniform magnetic field B perpendicular to its plane such that when rotated slightly about its diameter and released, it starts performing simple harmonic motion of time period T. If the mass of the loop is m then :
A
$$T = \sqrt {{{2m} \over {IB}}} $$
B
$$T = \sqrt {{{\pi m} \over {IB}}} $$
C
$$T = \sqrt {{{\pi m} \over {2IB}}} $$
D
$$T = \sqrt {{{2\pi m} \over {IB}}} $$
3
JEE Main 2020 (Online) 9th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A long, straight wire of radius a carries a current distributed uniformly over its cross-section. The ratio of the magnetic fields due to the wire at distance $${a \over 3}$$ and 2$$a$$, respectively from the axis of the wire is :
A
2
B
$${1 \over 2}$$
C
$${3 \over 2}$$
D
$${2 \over 3}$$
4
JEE Main 2020 (Online) 9th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A charged particle of mass 'm' and charge 'q' moving under the influence of uniform electric field $$E\overrightarrow i $$ and a uniform magnetic field $$B\overrightarrow k $$ follows a trajectory from point P to Q as shown in figure. The velocities at P and Q are respectively, $$v\overrightarrow i $$ and $$ - 2v\overrightarrow j $$ . Then which of the following statements (A, B, C, D) are the correct ?
(Trajectory shown is schematic and not to scale) : JEE Main 2020 (Online) 9th January Morning Slot Physics - Magnetic Effect of Current Question 112 English
(A) E = $${3 \over 4}\left( {{{m{v^2}} \over {qa}}} \right)$$

(B) Rate of work done by the electric field at P is $${3 \over 4}\left( {{{m{v^3}} \over a}} \right)$$

(C) Rate of work done by both the fields at Q is zero

(D) The difference between the magnitude of angular momentum of the particle at P and Q is 2mav.
A
(A), (B), (C), (D)
B
(A), (B), (C)
C
(A), (C), (D)
D
(B), (C), (D)
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