1
JEE Main 2019 (Online) 11th January Morning Slot
+4
-1
Three charges Q, + q and + q are placed at the vertices of a right-angle isosceles triangle as shown below. The net electrostatic energy of the configuration is zero, if the value of Q is :

A
$${{ - q} \over {1 + \sqrt 2 }}$$
B
+ q
C
$$-$$ 2q
D
$${{ - \sqrt 2 q} \over {\sqrt 2 + 1}}$$
2
JEE Main 2019 (Online) 11th January Morning Slot
+4
-1
The given graph shows variation (with distance r form centre) of :

A
Electric field of a uniformly charged sphere
B
Electric field of a uniformly charged spherical shell
C
Potential of a uniformly charged sphere
D
Potential of a uniformly charged spherical shell
3
JEE Main 2019 (Online) 10th January Evening Slot
+4
-1
Four equal point charges Q each are placed in the xy plane at (0, 2), (4, 2), (4, –2) and (0, –2). The work required to put a fifth charge Q at the origin of the coordinate system will be -
A
$${{{Q_2}} \over {4\pi {\varepsilon _0}}}$$
B
$${{{Q^2}} \over {2\sqrt 2 \pi {\varepsilon _0}}}$$
C
$${{{Q_2}} \over {4\pi {\varepsilon _0}}}\left( {1 + {1 \over {\sqrt 3 }}} \right)$$
D
$${{{Q_2}} \over {4\pi {\varepsilon _0}}}\left( {1 + {1 \over {\sqrt 5 }}} \right)$$
4
JEE Main 2019 (Online) 10th January Evening Slot
+4
-1
Charges –q and +q located at A and B, respectively, constitude an electric dipole. Distance AB = 2a, O is the mid point of the dipole and OP is perpendicular to AB. A charge Q is placed at P where OP = y and y >> 2a. The charge Q experiences an electrostatic force F. If Q is now moved along the equatorial line to P' such that OP' = $$\left( {{y \over 3}} \right)$$, the force on Q will be close to - $$\left( {{y \over 3} > > 2a} \right)$$

A
9F
B
3F
C
F/3
D
27F
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