I am tasked with the following exercise:
Electric charges of $+q$ are fixed at the four corners of a square of side-length a. (i) What is the electric potential at the centre of this square? (ii) If two of the charges are replaced by charges of $-q$, what now is the potential at the centre of the square? (iii) Does it matter for the electric potential which two charges are replaced? (iv) Does it matter for the electric field at the centre which two are replaced?
And I think this exercise requires me to understand how electric potential contributions are made with varying charge signatures.
For (i), I think the electric potential at the centre of the square should be maximum, as none of the electric potential contributions of each the charges should interfere with eachother. However, for (ii), the fact that potential here can switch sign challenges my knowledge further, and I can't figure out what will happen.
Need some guidance here.