Awhen a point charge of +q is placed on one corner of a square, an electric field strength of 2 n/c is observed at the center of the square. suppose three identical charges of +q are placed on the remaining three corners of the square. what is the magnitude of the net electric field at the center of the square?

You can use a symmetry argument to determine the net electric field at the center of the square.

Each one of the square's corners is equidistant from the center. You can then argue that the contribution to the field at the center from each charge is equal in magnitude.

You can also argue that, for any charge placed on the square, its contribution to the field can be matched with and canceled out by the contribution from the charge on the opposite corner (e.g. the contributions from the top-left and bottom-right charges will cancel out).

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