Question

Two point charges are fixed on the x–axis in otherwise empty space as shown below.

In which Region(s) is there a place on the x–axis (aside from infinity) at which the electric field is equal to zero?

(A) Only in Region II 

(B) Only in Region III 

(C) In both Regions I and II

(D) In both Regions I and III

(E) In both Regions II and III

Answer 1

The correct option is: (B) Only in Region III 

Explanation:

For E to be zero, the electric field vectors from each charge must point in opposite directions and must therefore occur at a point outside the charges. For the electric field vectors from each charge to be equal in magnitude so they can cancel, it must also occur at a point closer to the smaller charge to make up for the weaker field.