potential difference
A uniform electric field makes it easier to measure the difference in electric potential energy. This energy, also called the electric potential difference is commonly referred to as the voltage , based on the unit, volt V . To measure the voltage across some distance, it is necessary to pick a position to be the relative zero, because voltage is the change in potential difference. Any point in a system can be given the value of zero volts, but it is typically the point of a point charge or one plate in a uniform electric field as shown above. The voltage is measured using a voltmeter, which measures the electric potential difference across two points.