Saved Bookmarks
| 1. |
Obtain an expression for the electric potential energy of a systemof two point charges in the absence of an externalelectric field. |
|
Answer» Solution :Consider a system consisting of two point charges `q_1` and `q_2` separated by a distance `r_12` in free SPACE. Let the charge `q_1` be moved from infinityto the pointA . No WORK is doneduring this process as the charge `q_1` is moved in a field free region. Withthe charge `q_1` FIXED at A, let the other charge `q_2` be moved from infinityto the point B against the fielddue to charge `q_1`. Work done in this process is `W=V_Bq_2`...(1 ) `V_B` is potential at B due to `q_1` But `V_B=1/(4piepsilon_0)q_1/r_12` So equation (1) becomes `W=1/(4piepsilon_0)(q_1q_2)/r_12` This work done is stored in the FORM of potential energy of the system of two charges `q_1` and `q_2`. Hence `U=1/(4piepsilon_0)(q_1q_2)/r_12`. 
|
|