
Anyway, could someone help me with these:
Four charges of +4.0nC are situated at each of the corners of a square 0.1m wide.
Charges at points Q, R, S and P.
a)Determine electrostatic force on charge P
b) What is the electrostatic force on a -1nC charge placed at the centre of the square? Justify your answer.
For a) I got something like 2.75 x 10-5N on a bearing of 045. It took about 3 pages of working to get to this and I have no idea if it's right.
For b) I put 0N and waffled about vector sums adding to zero and the forces all cancelling out. Blah blah blah.
Also, derive E=V/d. It's probably in the sheets we were *supposed* to get last week
