In the figure below, how much work must we do to bring a particle, of charge Q =
ID: 2050971 • Letter: I
Question
In the figure below, how much work must we do to bring a particle, of charge Q = +16e and initially at rest, along the dashed line from infinity to the indicated point near two fixed particles of charges q1 = +4e and q2 = –q1/2? Distance d = 8.65 cm, 1 = 37°, and 2 = 60°.
In the figure below, how much work must we do to bring a particle, of charge Q = +16e and initially at rest, along the dashed line from infinity to the indicated point near two fixed particles of charges q1 = +4e and q2 = ?q1/2? Distance d = 8.65 cm, theta1 = 37 degree, and theta2 = 60 degree.Explanation / Answer
This can be easily solved using the concept of Potential.
Theory says that,
Work done by external force in bringing a charge from one point to another is equal the change in potential energy of that charge between those points.
Here, Initial point = Infinity.
So, Initial Potential Energy = 0.
Potential at Required point due to previous placed charges = K*q1/2d + K*q2/d [K = 1/4o = 9*109]
= K * (4e/2d - 2e/d)
= 0.
Since, potential at required point is zero, any charge placed there will have zero potential energy.
Final Potential Energy = 0.
Change in energy = 0. Hence work done by externnal force = 0 (zero).