Question

Charges $2q$ and $-q$ are placed at $(a,0)$ and $(-a,0)$ as shown in the figure. The x coordinates of the point at which electric field intensity is zero will be $(x,0)$ where :

• A. $-a<x<a$
• B. $x<-a$
• C. $x>-a$
• D. $0<x<a$

Answer 1

The correct option is B $x<-a$

For zero electric field intensity, point should not be between the tow charges as between the two charges, the direction due to both of the charges is same.

As electric field ($E=q/4\pi {ϵ}_o{r}^2$)is inversely proportional to the square of distance from charge, it should be nearer to the charge $-q$ compared to the charge $2q$.

So from above conditions, the point should be on left of the $-q$ charge i.e., $x<-a$