The relationship between uniform electric field intensity E and potential difference V across a separation d is

Explanation

For a uniform field, such as that between parallel plates, the intensity is the potential gradient, so a 100 V supply across plates 2 mm apart gives a field of 50,000 V per metre. This is why the unit volt per metre is equivalent to newton per coulomb. In a non uniform field the same relationship holds only as a local rate of change.