The electric potential difference \( V \) between two parallel plates can be calculated using the formula:
\[ V = E \cdot d \]
where:
- \( E \) is the magnitude of the electric field,
- \( d \) is the distance between the plates.
Given:
- \( E = 1250 , \text{N/C} \)
- \( d = 0.05 , \text{m} \)
Substituting the values into the formula:
\[ V = 1250 , \text{N/C} \cdot 0.05 , \text{m} = 62.5 , \text{V} \]
Rounding to the tenths place, the electric potential difference is:
\[ \boxed{62.5 , \text{V}} \]