Given resistance R = 12.5 and current I = 10 A.

Ohm's Law states that the potential difference ($V$) across a resistor is directly proportional to the current ($I$) flowing through it, and the constant of proportionality is the resistance ($R$).

$$V = IR$$

Given resistance $R = 12.5 \, \Omega$ and current $I = 10 \, A$.

$$V = (10 \, A) \times (12.5 \, \Omega)$$

$$V = 125 \, V$$

The potential difference across the resistor is 125 V.

$$\text{125 V}$$