Question

Assertion (A): Equal amount of positive and negative charges are distributed uniformly on two halves of a thin circular ring as shown in figure. The resultant electric field at the centre O of the ring is along OC.
Reason (R): It is so because the net potential at O is not zero. 

• A. If both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
• B. If both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of Assertion (A).
• C. If Assertion (A) is true but Reason (R) is false.
• D. If both Assertion (A) and Reason (R) are false.

Hint:

In electrostatics, the electric field due to symmetrically placed charges is directed along the symmetry axis. The potential, however, is scalar and adds algebraically, so for a system with symmetrical charge distribution, the net potential can be zero even when the electric field is not.

Answer 1

The Correct Option is A

In this case, the charges are symmetrically placed on the two halves of the ring, and their electric fields at the center will cancel out in the directions perpendicular to the line joining the charges. Thus, the resultant electric field at O is along the axis OC, as the symmetry of the charge distribution ensures a non-zero field in this direction.
However, the net potential at O is indeed zero. This is because the potential due to positive charges and negative charges at the center of the ring cancels out symmetrically, leaving the potential at O to be zero. Therefore, the reason given in (R) is incorrect.
Thus, the assertion (A) is true, but the reason (R) is false.