1
JEE Main 2020 (Online) 8th January Morning Slot
+4
-1
In finding the electric field using Gauss Law the formula $$\left| {\overrightarrow E } \right| = {{{q_{enc}}} \over {{\varepsilon _0}\left| A \right|}}$$ is applicable. In the formula $${{\varepsilon _0}}$$ is permittivity of free space, A is the area of Gaussian surface and qenc is charge enclosed by the Gaussian surface. The equation can be used in which of the following situation?
A
Only when $$\left| {\overrightarrow E } \right|$$ = constant on the surface.
B
For any choice of Gaussian surface.
C
Only when the Gaussian surface is an equipotential surface.
D
Only when the Gaussian surface is an equipotential surface and $$\left| {\overrightarrow E } \right|$$ is constant on the surface.
2
JEE Main 2020 (Online) 8th January Morning Slot
+4
-1
Three charged particle A, B and C with charges –4q, 2q and –2q are present on the circumference of a circle of radius d. the charged particles A, C and centre O of the circle formed an equilateral triangle as shown in figure. Electric field at O along x-direction is :
A
$${3{\sqrt 3 q} \over 4{\pi {\varepsilon _0}{d^2}}}$$
B
$${{\sqrt 3 q} \over 4{\pi {\varepsilon _0}{d^2}}}$$
C
$${{\sqrt 3 q} \over {\pi {\varepsilon _0}{d^2}}}$$
D
$${{2\sqrt 3 q} \over {\pi {\varepsilon _0}{d^2}}}$$
3
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
Two infinite planes each with uniform surface charge density to are kept in such a way that the angle between them is 30o. The electric field in the region shown between them is given by :
A
$${\sigma \over {{ \in _0}}}\left[ {\left( {1 + {{\sqrt 3 } \over 2}} \right)\widehat y + {{\widehat x} \over 2}} \right]$$
B
$${\sigma \over {2{ \in _0}}}\left[ {\left( {1 + \sqrt 3 } \right)\widehat y + {{\widehat x} \over 2}} \right]$$
C
$${\sigma \over {2{ \in _0}}}\left[ {\left( {1 + \sqrt 3 } \right)\widehat y - {{\widehat x} \over 2}} \right]$$
D
$${\sigma \over {2{ \in _0}}}\left[ {\left( {1 - {{\sqrt 3 } \over 2}} \right)\widehat y - {{\widehat x} \over 2}} \right]$$
4
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
Let a total charge 2Q be distributed in a sphere of radius R, with the charge density given by $$\rho$$(r) = kr, where r is the distance from the centre. Two charges A and B, of –Q each, are placed on diametrically opposite points, at equal distance, $$a$$ from the centre. If A and B do not experience any force, then :
A
$$a = {8^{ - 1/4}}R$$
B
$$a = {2^{ - 1/4}}R$$
C
$$a = {{3R} \over {{2^{1/4}}}}$$
D
$$a = {R \over {\sqrt 3 }}$$
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