1
JEE Main 2021 (Online) 20th July Morning Shift
+4
-1
A current of 5 A is passing through a non-linear magnesium wire of cross-section 0.04 m2. At every point the direction of current density is at an angle of 60$$^\circ$$ with the unit vector of area of cross-section. The magnitude of electric field at every point of the conductor is :

(Resistivity of magnesium $$\rho$$ = 44 $$\times$$ 10$$-$$8 $$\Omega$$m)
A
11 $$\times$$ 10$$-$$5 V/m
B
11 $$\times$$ 10$$-$$3 V/m
C
11 $$\times$$ 10$$-$$7 V/m
D
11 $$\times$$ 10$$-$$2 V/m
2
JEE Main 2021 (Online) 20th July Morning Shift
+4
-1
A certain charge Q is divided into two parts q and (Q $$-$$ q). How should the charges Q and q be divided so that q and (Q $$-$$ q) placed at a certain distance apart experience maximum electrostatic repulsion?
A
Q = 2q
B
Q = 4q
C
Q = 3q
D
Q = $${q \over 2}$$
3
JEE Main 2021 (Online) 18th March Morning Shift
+4
-1
An oil drop of radius 2 mm with a density 3g cm$$-$$3 is held stationary under a constant electric field 3.55 $$\times$$ 105 V m$$-$$1 in the Millikan's oil drop experiment. What is the number of excess electrons that the oil drop will possess? (consider g = 9.81 m/s2)
A
48.8 $$\times$$ 1011
B
1.73 $$\times$$ 1010
C
17.3 $$\times$$ 1010
D
1.73 $$\times$$ 1012
4
JEE Main 2021 (Online) 16th March Evening Shift
+4
-1
Find out the surface charge density at the intersection of point x = 3 m plane and x-axis, in the region of uniform line charge of 8 nC/m lying along the z-axis in free space.
A
0.424 nC m$$-$$2
B
4.0 nC m$$-$$2
C
47.88 C/m
D
0.07 nC m$$-$$2
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