1
WB JEE 2020
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Four identical point masses, each of mass m and carrying charge + q are placed at the corners of a square of sides a on a frictionless plane surface. If the particles are released simultaneously, the kinetic energy of the system when they are infinitely far apart is
A
$${{{q^2}} \over a}(2\sqrt 2 + 1)$$
B
$${{{q^2}} \over a}(\sqrt 2 + 2)$$
C
$${{{q^2}} \over a}(\sqrt 2 + 4)$$
D
$${{{q^2}} \over a}(\sqrt 2 + 1)$$
2
WB JEE 2020
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A very long charged solid cylinder of radius a contains a uniform charge density p. Dielectric constant of the material of the cylinder is K. What will be the magnitude of electric field at a radial distance x (x < a) from the axis of the cylinder?
A
$$p{x \over {{\varepsilon _0}}}$$
B
$$p{x \over {{2k\varepsilon _0}}}$$
C
$$p{{{x^2}} \over {2a{\varepsilon _0}}}$$
D
$$p{{{x^{}}} \over {2k}}$$
3
WB JEE 2020
MCQ (Single Correct Answer)
+2
-0.5
Change Language
A pair of parallel metal plates are kept with a separation d. One plate is at a potential + V and the other is at ground potential. A narrow beam of electrons enters the space between the plates with a velocity v0 and in a direction parallel to the plates. What will be the angle of the beam with the plates after it travels an axial distance L?
A
$${\tan ^{ - 1}}\left( {{{eVL} \over {md{v_0}}}} \right)$$
B
$${\tan ^{ - 1}}\left( {{{eVL} \over {mdv_0^2}}} \right)$$
C
$${\sin ^{ - 1}}\left( {{{eVL} \over {md{v_0}}}} \right)$$
D
$${\cos ^{ - 1}}\left( {{{eVL} \over {mdv_0^2}}} \right)$$
4
WB JEE 2020
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Two pith balls, each carrying charge + q are hung from a hook by two springs. It is found that when each charge is tripled, angle between the strings double. What was the initial angle between the strings?
A
30$$^\circ $$
B
60$$^\circ $$
C
45$$^\circ $$
D
90$$^\circ $$
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