Two point charges +Qand -Q_(2)areplaced at A and B respectively . A lineof forceemanates from Q_(1)at an angletheta with line joining A and B . Atwhatanglewill itterminate at B ?

Two point charges +Qand -Q_(2)areplaced at A and B respectively . A li

1.	Two point charges +Qand -Q_(2)areplaced at A and B respectively . A lineof forceemanates from Q_(1)at an angletheta with line joining A and B . Atwhatanglewill itterminate at B ?
Answer» Solution :We knowthat numberof emerging lines offorce f is PROPORTIONAL to magnitude of the change. Thefieldlines emanating from Q1 are spread out EQUALLY in all direction . The number of fieldlines or flux through cone ofhalfangle `theta` is `(Q_(1))/(4pi)2pi (1- cos theta)` Similary the numberof linesof force terminatingon `-Q_(2)` ATAN angle `phi` is `(Q_(2))/(4pi) 2pi (1- cosphi)` . The total lines of force emanating from `Q_(1)` is EQUAL to the totallines of froceterminatingon `Q_(2)` `rArr (Q_(1))/(4pi) 2pi(1-cos theta) = (Q_(2))/(4pi)2pi(1-cosphi)` or`(Q_(1))/(2)(1- cos theta) = (Q_(2))/(2)(1- cos phi)` `Q_(1) sin^(2) theta // 2 = Q_(2) sin^(2) phi //2` `rArr phi = 2 sin^(-1){ sqrt((Q_(1))/(Q_(2))) sin theta//2}`