According to wikipedia the definition of electric potential difference is as follows:
The difference in electric potential between two points (i.e., voltage) is defined as the work needed per unit of charge against a static electric field to move a test charge between the two points.
Imagine a simple circuit one variable resistor connected to a 12v battery. An electric field is created between the + and - pole of the battery. The difference in electric potential is apparently constant when measured across the resistor independent of it's resistance.
Intuitively I would say that the work needed for a unit of charge to pass a with resistance $a$ is larger than for a resistance $b$ where $a>b$. This implies that that the potential difference across the resistor is greater for $a$ than for $b$. Why am I wrong?