Four charges q1, q2, q3 and q4 are placed at the positions as shown in the figure, given q1 +q2+ q3 + q4 = 0 . The electric field on z-axis  
  • a)
    is always along +ve z-axis  
  • b)
    is always along −ve z-axis  
  • c)
    is always zero on z-axis  
  • d)
    may be perpendicular to z-axis or zero on z-axis depending on charges 
Correct answer is option 'D'. Can you explain this answer?

Related Test

Answers

Satvir Kaur
Jul 22, 2020
As q1 +q2 + q3 + q4 = 0 , z axis is an equipotential line. Thus electric field is either zero or perpendicular to the z-axis. When q2 = q4 and q3 = q1 electric field is zero at origin and in all other cases it is perpendicular to z-axis. 

As q1 +q2 + q3 + q4 = 0 , z axis is an equipotential line. Thus electric field is either zero or perpendicular to the z-axis. When q2 = q4 and q3 = q1 electric field is zero at origin and in all other cases it is perpendicular to z-axis.
As q1 +q2 + q3 + q4 = 0 , z axis is an equipotential line. Thus electric field is either zero or perpendicular to the z-axis. When q2 = q4 and q3 = q1 electric field is zero at origin and in all other cases it is perpendicular to z-axis.