1
JEE Main 2019 (Online) 9th January Morning Slot
+4
-1
Three charges + Q, q, + Q are placed respectively, at distance, 0, d/2 and d from the origin, on the x-axis. If the net force experienced by + Q, placed at x = 0, is zero, then value of q is :
A
$$-$$ $${Q \over 4}$$
B
+ $${Q \over 2}$$
C
+ $${Q \over 4}$$
D
$$-$$ $${Q \over 2}$$
2
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$$\sqrt 2$$
3
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
$${{F} \over 2}$$
4
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
$${\sigma \over { \in {}_0}}\left[ {{{{b^2} - {c^2}} \over b} + a} \right]$$
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