Positive charge +Q is uniformly distributed on the upper half of a semicircular rod and negative charge -Q is uniformly distributed on the lower half.What is the direction of the electric field at point P, the center of the semicircle?
A)" $\uparrow$ "
B)" $\downarrow$ "
C)" $\leftarrow$ "
D)" $\rightarrow$ "
E) ""

Question

Positive charge +Q is uniformly distributed on the upper half of a semicircular rod and negative charge -Q is uniformly distributed on the lower half.What is the direction of the electric field at point P, the center of the semicircle? 
A)" $\uparrow$ " 
B)" $\downarrow$ " 
C)" $\leftarrow$ " 
D)" $\rightarrow$ " 
E) ""

Quizplus · Accepted Answer

At point P, the electric field due to the upper half of the semicircular rod is directed downwards and the electric field due to the lower half of the semicircular rod is directed upwards. The magnitudes of these fields are equal due to the uniform charge distribution. Therefore, the net electric field at point P is directed upwards, perpendicular to the plane of the semicircle. Therefore, the correct choice is B, which shows the electric field pointing upwards.

Positive Charge +Q Is Uniformly Distributed on the Upper Half ↑\uparrow↑

Positive Charge +Q Is Uniformly Distributed on the Upper Half $\uparrow$