Electric potential is not electric field
The mistake
Using V and E interchangeably, or assuming E = 0 wherever V = 0.
Why it feels right
Both describe 'how strong the electricity is' in casual terms.
How to catch it
You equated volts with volts per meter, or inferred one directly from the other's zero.
The first principle
Field is the negative gradient of potential: E_x = −dV/dx. V can be zero where E is nonzero, and V is constant throughout a region where E = 0.
worked mini-example
At the midpoint between +q and −q, what are V and E?
Common wrong move
Both zero.
Correct
V = 0, but E is non-zero (points from + to −).
Test the repair CIR-03 · transfer
include V/m
Make a fresh prediction before referring to the worked example.