Two Uniform Rods, Each of Length 2

Multiple Choice

Two uniform rods, each of length 2.0 m, are bent to form semicircles. One rod has a charger per unit lent of 1.5 nC/m, and the other has a charge per unit length of -1.5 nC/m. The semicircles are joined to make a circle. What is the magnitude of the electric field at the center of the circle?

A) 42 N/C
B) 84 N/C
C) 34 N/C
D) 68 N/C
E) 0