1
JEE Main 2019 (Online) 12th January Morning Slot
+4
-1
Determine the electric dipole moment of the system of the three charges, placed on the vertices of an equilateral triangle, as shown in the figure :

A
$$2q\ell \widehat j$$
B
$$\left( {q\ell } \right){{\widehat i + \widehat j} \over {\sqrt 2 }}$$
C
$$\sqrt 3 \,q\ell {{\widehat j - \widehat i} \over {\sqrt 2 }}$$
D
$$- \sqrt 3 \,q\ell \widehat j$$
2
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
$${{ - \sqrt 2 q} \over {\sqrt 2 + 1}}$$
3
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
4
JEE Main 2019 (Online) 10th January Morning Slot
+4
-1
A charge Q is distributed over three concentric spherical shells of radii a, b, c (a < b < c) such that their surface charge densities are equal to one another. The total potential at a point at distance r from their common centre, where r < a, would be -
A
$${{Q\left( {{a^2} + {b^2} + {c^2}} \right)} \over {4\pi {\varepsilon _0}\left( {{a^3} + {b^3} + {c^3}} \right)}}$$
B
$${Q \over {4\pi {\varepsilon _0}\left( {a + b + c} \right)}}$$
C
$${Q \over {12\pi {\varepsilon _0}}}{{ab + bc + ca} \over {abc}}$$
D
$${{Q\left( {a + b + c} \right)} \over {4\pi {\varepsilon _0}\left( {{a^2} + {b^2} + {c^2}} \right)}}$$
JEE Main Subjects
Physics
Mechanics
Electricity
Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
Mathematics
Algebra
Trigonometry
Coordinate Geometry
Calculus
EXAM MAP
Joint Entrance Examination