In Fig., a thin rod forms a semicircle of radius r = 3.00 cm. Charge is uniformly distributed along the rod, with +q = 4.50 pC in the upper half and -q = -4.50 pC in the lower half. What are the (a) magnitude and (b) direction (relative to the positive direction of the x axis) of the electric field `vec(E)` at P, the center of the semicircle ?

Explanation

(a) 57.2 N/C, (b) `-90^(@)` counterclockwise from the `.^(+)(x)` axis