Saved Bookmarks
| 1. |
(a) Depict the equipotential surfaces for a system of two identical positive point charges placed a distance 'd' apart. (ii) Deduce the expression for the potential energy of a system of two point charges q_1 and q_2 brought from infinity of the points vecr_1 and vecr_2 respectively in the presence of external electric field vecE. |
|
Answer» Solution :(a) Equoipotential surfaces of two identical postive POINT charges placed at a distance 'd' apart. (b) (a) Let ` vecE` be the external field. ` therefore` Work done one ` q_2` against the external field ` =q_2.V(r_2)` Work done on `q_2` against the filed due to ` q_1=(1)/(4 pi epsilon_0) .(q_1q_2)/(r_12)=(q_1q_2)/(4pi epsilon _0r_12)` where `r_12` is the distance between `q_1 and q_2`. By the SUPER position principle for fields, we add up the work on `q_2` against the two fields (`vecE` and that due to`q_1`). Therefore, work done in bringing `q_2` to `vecr_2`. `=q_2.V(vecr_2)+(q_1q_2)/(4piepsilon_0r_12)` Thus, the POTENTIAL energy of the SYSTEM = the total work done in assembling the configuration. `=q_1.V(vecr_1)+q_2+(q_1q_2)/(4piepsilon_0 r_12)`. 
|
|