A uniformly charged insulating rod of length 12.0 cm is bent into the shape of a semicircle as shown in the figure below. The rod has a total charge of −7.50 µC.
Find the magnitude of the electric field at O, the centre of the semicircle.
E = 2kq / pi r2
(Acquired on the internet)
The Attempt at a Solution
E = 2(9X109)(-7.5X10-6) / pi (0.06)2
E = -135000 / 0.01130973355
E = -11936620.73
magnitude: 11936620 N/C
Got it wrong... I don't know why...