Hi

@user69608 hi :-)

i have a doubt about stable equilibrium will send some pics in a while

OK ... ?

this is from feynman's book

OK. What's your question?

i found something contradicting i guess i am sending wait

in this question in part (e).isn't this disobeying what feynman said in the first image

Note that in this case the central charge has the same sign as the charges at the corners. In Feynmann's example the central charge had the opposite sign to the charges at the corners.

how did he conclude that equilibrium can not be stable

also what does "there are no points of stable equilibrium in any electrostatic field-except right on the top of another charge

in this he says "in any electrostatic field" then how will that matter if central charge is positive or not?

Good point. I'll have to go away and think about it.

yes sure