Two very large parallel sheets a distance d apart have their centers directly opposite each other. the sheets carry equal but opposite uniform surface charge densities. a point charge that is placed near the middle of the sheets a distance d/2 from each of them feels an electrical force f due to the sheets. if this charge is now moved closer to one of the sheets so that it is a distance d/4 from that sheet, what force will feel?

(a) f
(b) 4f
(c) 2f
(d) f/2
(e) f/4

Option (A) is the correct answer.

Explanation:

According to the Gauss law, electric field due to very large sheet of charge is as follows.

                    E =

where,     = charge per unit area

Since, it is given that there are two sheets of equal and opposite charge. Therefore, electric field between the plates will be as follows.

                  E =

Also, we know that relation between force and electric field is as follows.

                       F = qE

Hence, force felt by the charge present inside the plates will be as follows.

                    F =

This shows that force is not dependent on the distance and the charge is kept from one of the plate. Therefore, we can say that the force F felt by the charge is same when it is placed at a distance and at a distance from one of the plate.

Thus, we can conclude that the force we will feel is F.

12000j is work done

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.