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) 12th January Morning Slot
+4
-1
There is a uniform spherically symmetric surface charge density at a distance R0 from the origin. The charge distribution is initially at rest and starts expanding because of mutual repulsion. The figure that represents best the speed V (R(t)) of the distribution as a function of its instantaneous radius R (t) is :
A
B
C
D
3
JEE Main 2019 (Online) 11th January Evening Slot
+4
-1
An electric field of 1000 V/m is applied to an electric dipole at angle of 45o. The value of electric dipole moment is 10–29 C.m. What is the potential energy of the electric dipole?
A
- 7 $$\times$$ 10–27 J
B
$$-$$ 9 $$\times$$ 10–20 J
C
$$-$$ 10 $$\times$$ 10–29 J
D
$$-$$ 20 $$\times$$ 10–18 J
4
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
$${{ - \sqrt 2 q} \over {\sqrt 2 + 1}}$$
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