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) $\rightarrow$

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) $\rightarrow$

Quizplus · Accepted Answer

At point P, the electric field due to the positive charge and negative charge will be in opposite directions. The direction of electric field due to positive charge is radial and pointing away from the center of the semicircle. The direction of electric field due to negative charge is also radial, but pointing towards the center of the semicircle. At the center of the semicircle, these two electric fields cancel each other out and result in a net electric field of zero.

Since the electric field lines are continuous, they must be tangent to the semicircle at point P. The only option that shows an electric field direction that is tangent to the semicircle at point P is option B: F1F1F1S1F1F1F10.

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

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