InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
Three point charges ` Q, 4 Q` and ` 16 Q` are placed on a straight line ` 9 cm` long. Charges are placed in such a wat that the system has minimum potential energy . Then .A. `4Q` and `16 Q` must be at the ends and `Q` at a distance of `3` cm from the `16Q`B. `4Q` and `16 Q` must be at the ends and `Q` at a distance of `3` cm from the `16Q`C. Electric field at the position of `Q` at a distance of `6 cm` from the `16 Q`.D. Electric field at the position of `Q` at a distance of `6 cm` from the `16 Q`. |
|
Answer» Correct Answer - B::C For potential enrgy to be minmuum charge ` 11 Q` and ` 16Q` to be placed at the ebd of line ` U = (Kq_1q_2)/r_(12) + (Kq_1q_3)/r_(13) + (Kq_2q_3)/r_(23)` `U= (K. 4Q.Q)/((9-x) xx 10^(-12)) + (K. (4 Q) 16Q)/((9) xx 10^(-2)) + (KQ.16Q)/x` ` U= 4/((9-x)) + 100KA^2 . (64)/9 + 100 KQ^2` for `U` to be minimum `(dU)/(dx) =0` `1/((9-0x)^2) = 4/x^2` `(0-x)^2 x^2` ` x= 6 cm or 18 cm` since ` F=- (dU)/(dx) rArr F0.`, when `U` is min. |
|