Lectures on Physics has been derived from Benjamin Crowell's Light and Matter series of free introductory textbooks on physics. See the editorial for more information....

Relating the units of electric field and voltage

From our original definition of the electric field, we expect it to have units of newtons per coulomb, N/C. The example above, however, came out in volts per meter, V/m. Are these inconsistent? Let's reassure ourselves that this all works. In this kind of situation, the best strategy is usually to simplify the more complex units so that they involve only mks units and coulombs. Since voltage is defined as potential energy per unit charge, it has units of J/C:

To connect joules to newtons, we recall that work equals force times distance, so J=N.m, so

As with other such difficulties with electrical units, one quickly begins to recognize frequently occurring combinations.

Last Update: 2009-06-21