A square has equal positive charges at three of its corners and a negative charge at the third. The direction of the electric field at point P is

Question

Quizplus · Accepted Answer

Based on the given information, we can draw a diagram of the charges at the corners of the square and use the principle of superposition to determine the direction of the electric field at point P. By adding up the electric field contributions from each individual charge, we find that the net electric field points in the direction shown in choice B.

To see this, consider the electric field from the positive charge q at the upper left corner of the square. This field points to the right and downward, since the positive charge repels positive test charges and attracts negative ones. Similarly, the electric field from the positive charge q at the upper right corner points downward and to the left, while the electric field from the positive charge q at the lower left corner points upward and to the right.

Finally, the electric field from the negative charge -q at the lower right corner points to the left and upward, since negative charges attract positive test charges and repel negative ones. When we add up these four electric field vectors, we find that they combine to produce a net electric field pointing in the direction shown in choice B.

A Square Has Equal Positive Charges at Three of Its