1
JEE Main 2019 (Online) 9th January Morning Slot
+4
-1
For a uniformly charged ring of radius R, the electric field on its axis has the largest magnitude at a distance h from its center. Then value of h is :
A
$${R \over {\sqrt 5 }}$$
B
$${R \over {\sqrt 2 }}$$
C
R
D
R$$\sqrt 2$$
2
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
Two identical conducting spheres A and B, carry equal charge. They are separated by a distance much larger than their diameters, and the force between theis F. A third identical conducting sphere, C, is uncharged. Sphere C is first touhed to A, then to B, and then removed. As a result, the force between A and B would be equal to :
A
F
B
$${{3F} \over 4}$$
C
$${{3F} \over 8}$$
D
$${{F} \over 2}$$
3
JEE Main 2018 (Offline)
+4
-1
Three concentric metal shells A, B and C of respective radii a, b and c (a < b < c) have surface charge densities $$+ \sigma$$, $$- \sigma$$ and $$+ \sigma$$ respectively. The potential of shell B is :
A
$${\sigma \over { \in {}_0}}\left[ {{{{b^2} - {c^2}} \over c} + a} \right]$$
B
$${\sigma \over { \in {}_0}}\left[ {{{{a^2} - {b^2}} \over a} + c} \right]$$
C
$${\sigma \over { \in {}_0}}\left[ {{{{a^2} - {b^2}} \over b} + c} \right]$$
D
$${\sigma \over { \in {}_0}}\left[ {{{{b^2} - {c^2}} \over b} + a} \right]$$
4
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
A solid ball of radius R has a charge density $$\rho$$
given by $$\rho$$ = $$\rho$$o (1 $$-$$ $${\raise0.5ex\hbox{\scriptstyle r} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{\scriptstyle R}}$$) for 0 $$\le$$ r $$\le$$ R. The electric field outside the ball is :
A
$${{{\rho _o}{R^3}} \over {{ \in _o}{r^2}}}$$
B
$${{{\rho _o}{R^3}} \over {12{ \in _o}{r^2}}}$$
C
$${{4{\rho _o}{R^3}} \over {3{ \in _o}{r^2}}}$$
D
$${{3{\rho _o}{R^3}} \over {4{ \in _o}{r^2}}}$$
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