Three point charges q, 2q and 8q are to be placed on a
. 9cm long straight line. Find the
. positions where the charges shouldbe placed such that the potential energy
. of this sysrem is minimum. In this situation, what is the
. electric field at the charge q due to the other two charges?

Answer

`(##ALN_PHY_C01_E01_334_A01##)` , `E=0`

Explanation

For minimum potential energy of the system, q should be placed in the middle

`U_("system")=(K2qxxq)/(x) xx100+(Kq8q)/((9-x))xx100+((Kxx2qxx8q)/9)xx100`
`(dU)/(dx)=Kq^(2)xx100 [(-2)/x^(2)+8/((9-x)^(2))+0] rArr x=3 cm`
Electric field at the position of
`q=(Kxx2q)/((0.03)^(2))-(Kxx8q)/((0.06)^(2))=0`