Question

A positive charge experiences a force F when placed at point X in a uniform electric field. The charge is then moved from point X to point Y. Distances r and s are shown on the diagram.

IF you want to see the diagram here is the link:
http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Physics%20%289702%29/9702_s08_qp_1.pdf

Scroll down to Q. No.) 16 you'll see it
Someone told me that it might have something to do with vector rule but I don't know how to use it; help anyone?

Answer 1

Change in potential energy is always equal to the opposite of the work done by the force.
This should help you solve the problem.

Answer 2

Opposite of the work done by force?
wait you mean the force F on the charge times the distance s?

Answer 3

Definitely.

Answer 4

thank you very much; but I came across this question and I didn't understand a single thing this answerer was writing

http://openstudy.com/study#/updates/4f9fb580e4b01d279f25edac

Answer 5

the question is exactly the same as mine

Answer 6

Lots of unnecessary things in this answer.
Just remember what I wrote above.

It is true that the potential decreases when you go down the field lines, but as for energy, it depends whether the test charge is positive or negative.
So better remember the rule with the force because it always holds.

Answer 7

Alright thank you very much!!!

Answer 8

yw :)