Question

23. A dipole is placed in constant electric field E as shown. If it is released from rest from this
Гry
position, find the kinetic energy gained when it is parallel to electric field vector.
(Assume dipole is small and placed in a gravity free space)​

Answer 1

Given: A dipole is placed in constant electric field E as shown.

To find: The kinetic energy gained when it is parallel to electric field vector.

Solution:

• Now we have given that dipole is placed parallel to electric field.

• So, that means:

• p cos Ф is parallel to E, where Ф is angle between  E and vector.

• So now:

• W = -pE ( cos Ф(2) -  cos Ф(1) ) ................(i)

• Here Ф(1) will be zero degree as the vector is aligned at that angle, so  cos 0 = 1.

• Now by work energy theorem, we have:

                W = ΔK

• So from (i), we get:

                ΔK = -pE ( cos Ф(2) -  1 )

                ΔK = pE ( 1 - cos Ф(2) )

Answer:

               So the kinetic energy gained when it is parallel to electric field vector is  pE ( 1 - cos Ф(2) )

Answer 2

Answer:

pE(1-cos theta)

Explanation:

Refer image